Keihin Carburetors

                         Table of Contents

00. Keihin   carb ID     years     US model / Euro model x speed, engine
====================  M O P E D S  ====================
01. Keihin 50A, 50B1966-68 Honda P50 xxxxxxxxxxxx  40 kmh OHC
02. Keihin 610 (50B) 1967-68 Honda P50 Little Honda     40 kmh OHC
02. Keihin C4B, C5B  1969-70 Honda PC50A xxxxxxx  40,50 kmh OHC
03
. Keihin C5A, C5A  1969-70 Honda PC50 Little Honda   40 kmh OHC
03. Keihin S4A, S5A   1969-70 Honda PS50  xxxxooo x
40,50 kmh OHC
03. Keihin F4A, F5A  1970-73 Honda PC50K1, PF50 x
40,50 kmh OHV
03. Keihin S4B, S5B   1970-71 Honda PS50  xxxxxxxxooo
50 kmh OHV
03. Keihin PA 00A-A  1973-77 Honda PC50K1, PF50R ooo 50 kmh OHV

03. Keihin PA 01A-A  1973-77 Honda PC50K1, PF50R ooo 40 kmh OHV

04. Keihin PA M0A-A  1978-83
Indian AMI50 4-Stroke xx    30 mph OHV

0
4. Keihin BB
21A-B  1978-79 Honda PA50-I Hobbit xxx    20 mph TS
05. Keihin BB
20A-C  1978-83 Honda PA50-II Hobbit xx     30 mph TS
0
5. Keihin P 006A-A  1974-75 Honda MR50 Elsinore xxx   40 kmh OHC
0
5. Keihin PA 06A-A  1973-78 Honda PM50, PF50M xxxx   40 kmh TS
0
5. Keihin PA 07A-A  1975-78 Honda PF50M xxxxxxxxx    50 kmh TS
0
6. Keihin PA 08B-A  1977-78 Honda NC50 Express xxx    30 mph TS
06. Keihin PA 08B-B  1977-79 Honda NC50, NA50  xxxx   
30 mph TS
06. Keihin PA 08C-A  1978-79 Honda NC50, NA50  xxxx   
30 mph TS
06. Keihin PA 08E-A  1980-80 Honda NC50 Express xxx    30 mph TS
06. Keihin PA 08E-B  1980-80 Honda NC50 Express xxx    30 mph TS
06. Keihin PA 08D-A  1980-80 Honda NA50 Express II xx   30 mph TS
0
7. Keihin PA 15A-A  1981-81 Honda NC50 Express xxx    30 mph TS
07. Keihin PA 16A-A  1981-81 Honda NA50 Express II xx   30 mph TS
0
8. Keihin PA 13B-A  1981-82 Honda NX50 Express SR x   30 mph TS
08. Keihin PA 13B-B  1982-83 Honda NC50 Express xxx    30 mph TS

08. Keihin PA 13E-A  1982-83 Honda NU50 Urban Express 30 mph TS

08. Keihin PA 25A-A  1982-83 Honda NC50I, NU50I xxx     25 mph TS

08. Keihin PA 29C-D  1984-87 Honda NQ50, NB50 xxxxx   30 mph TS

=================  M I N I   C Y C L E S  ==================
09. Keihin PA   Z502  1968-71 Honda Z50A Mini Trail xxx 00 mph OHC
10. Keihin PA 655-A  1972-75 Honda Z50A Mini Trail xxx oo mph OHC
11. Keihin PA 674-A  1970-75 Honda QA50  xxx oooo xxx 00 mphOHV
11. Keihin PA 03A-A  1976-78 Honda Z50A Mini Trail xxx oo mph OHC
12. Keihin PA 03C-A  1979-81 Honda Z50R
12. Keihin PA 03D-A  1982-85 Honda Z50R
12. Keihin PA 03F-B  1986-87 Honda Z50R
12. Keihin PA 03H-A  1988-91 Honda Z50R
12. Keihin PA 03H-B  1988-91 Honda Z50R
14. Keihin PA 03M-A  1992-99 Honda Z50R
14. Keihin PA 03N-A  1992-99 Honda Z50R
13. Keihin PA 42A-C  2000-03 Honda XR50R
15. Keihin PA 42A-C  2004-09 Honda CRF50F
=================  M O T O R C Y C L E S  ==================
14. Keihin PB 15A-A  1982-83 Honda C70 Passport

=================  K E I H I N   P A R T S  ==================
15. Float needles

16. Float bowls

17. Gaskets and o-rings

18. Jets

 


Keihin

Welcome

Keihin carburetors are used on almost all Honda motorcycles (or copies of Hondas). Here we focus on the 50cc moped, mini-cycle and scooter carburetors mostly from the 1970’s and 1980’s. 

From WikipediaThe Keihin Corporation was founded December 19, 1956 and currently maintains its head office in Shinjuku Ward, Tokyo, Japan. Among the products they are internationally known for is the production of carburetors and fuel injection, and is a major suppler to Honda, and also Triumph, Suzuki, Kawasaki, KTM and Harley Davidson motorcycles. In addition to carburetors, Keihin supplies the automotive industry with engine, transmission and climate control products, including intake manifold assemblies, HVAC assemblies, compressors, valves, solenoids and electronic control units. Keihin’s largest shareholder is Honda Motor Co. Ltd. Keihin first began U.S. manufacturing in 1989. Counting all U.S. locations, Keihin has more than 20,000 employees. Keihin North America’s corporate headquarters is in Anderson, Indiana.

Flange holes 42, 38, 32 mm

Keihin motorcycle carburetors are labeled with a cast-in model ID prefix followed by several numbers and letters that specify the carburetor version for that application. Most of these Honda moped, noped, mini-cycle, scooter and small motorcycle carbs are Keihin prefix “PA”. Other Keihin motorcycle carburetor model codes are PB, PC, PD, PJ, PWK, CV, CVK, VB, VD, VE.

Flange mount: The Keihin PA family of carburetors are flange mount. Flange mount carbs have a diamond shape mounting flange with bolts on either side of the main air hole. The bolt holes can have different spacing.

Carburetor replacement: When replacing a carburetor the new carb must have the same bolt hole spacing. There is a way to get around this by making the bolt holes into slots. With slotted mount holes the flange mount carb is not automatically centered, so it has to be manually positioned in the center as the mount bolts are tightened.

 

 


Mopeds

P50 carb service

1. Keihin 
carb model code years  frame number range      models
50A-000 #044 1966-67 P25-A000001-00000 Honda P25
50A-610 #044 1967-68 P50-100001-148606 Honda P50
50A-610 #044 1967-68 P50-100001-148606 Honda P50 Little Honda (US)
50B-NL   #044 1967-68 P50-128651-148606 Honda P50 (Netherlands)

50B-000 #044 1968-68 P50-148607-000000 Honda P50

50B-000 #044 1968-68 P50-148607-000000 Honda P50 Little Honda (US)

Links to Images:
1966 Honda P25 (NL model)    1967 Honda P50    1968 Honda P50 (US model) 

Bore:  42.0 mm, stroke 35.6 mm, displacement: 49.3 cc. P50’s have down-draft carburetors, unusual.
50B carbs do not have a replaceable float valve. It’s part of, and only sold with, the float chamber cover.
50B has a larger carb size ∅11? and  jet #68 or 62. 50A has a smaller carb size ∅9? and jet #60 or 55.

Honda P50 carburetors

  =00 quantity   Keihin
0#=00
⇓⇓⇓⇓   
 (a)50A  (b)50A-610  (c)50B-N  (d)50B
0#=00 abcd  price   Honda part#x  description xxx specs
00=00 1000 N/A 16100-044-030  
00=00 1000N/A 16100-044-315 carburetor 50A-000 ’66-67

00=00 0100  N/A
16100-044-405 carburetor 50A-610 ’67-68
00=00 1100N/A 16010-044-004 gasket set 10-piece 4 12 13
00=00 1100  N/A 16010-044-004 15 20 20 20 24 27 32
08=00 1100N/A 16151-044-681 jet needle

11=00 1100  N/A 16125-044-004
float valve set
12=00 1100N/A 16173-001-004
rubber seal ring
13=00 1100N/A 16188-044-004 valve fiber washer 7.2 x 10.5
16=00 1000N/A 16133-044-004 needle jet

16=00 0100  N/A 16133-044-681 needle jet 2.6 x 1.55
17=00 1000  N/A 0-99144-03804 slow jet 38
17=00 0100N/A 0-99144-03504 slow jet 35

24=00 1100N/A 16123-044-004
jet access gasket
25=00 1000N/A 0-99120-06014 main jet 60

25=00 0100  N/A 0-99120-05514 main jet 55
26=00 1100  N/A 16112-044-004 float chamber cover
30=00 4400  0$1 0-93600-04008 sunk-phillips screw M4 x 8M4 x 8
32=00 1100N/A (not sold separately) choke shaft o-ring
=======================================
00=00 0010N/A 16100-044-681 carburetor 50B-NL 67-68
0
0=00 0001  N/A 16100-044-683 carburetor 50B-00 1968

01=00 0011 $18 16010-044-680 gasket set 4-piece 4 15 20 27
1n=27 1111 0$6
 16174-044-004 float o-ring 1.25 x 38 (40.5od)
1p=04
1111 0$5 16171-044-004 top rubber washer 10 x 15 x 1
1r=15 1111 0$5 16175-001-004 needle jet o-ring  2 x 4 (8od)
1i =20 3333 0$2 16175-260-004 jet/screw o-ring 2 x 2.5 (6.5od)

02=00 0011  N/A 16012-044-681 needle set 2a 2b 2c 2d
2a=06 1111 0$5 16156-044-004 throttle w-clip
2b=07 1111 0$2 16157-044-004 needle e-clip 1.5 for 2.0 needle
2c=00 0011  N/A 16151-044-683 jet needle
2d=00 0011  N/A 16133-044-683 needle jet 2.6 x 2.0
03=00 1111  N/A 16014-044-004 top set 3a 3b 1p
3a
=03 1111  N/A 16119-044-004 carb top M16-1.0
3b=02 1111 0$3 16118-044-004 cable adjuster male M6-0.75

04=00 0011  N/A 16015-044-014 chamber/valve set 4a 1n
4a=00 0011  N/A 16112-044-014
chamber cover w/valve
05=00 1111  N/A 16016-044-014 screw set 5a 5b 5c 5d 1i 1i
5a=18 1111  N/A 16163-044-014 idle speed screw
5b=19 1111
N/A 16162-259-004 idle air screw
5c=21 1111  N/A 16182-011-004 idle speed spring
5d=22 1111  N/A 16181-202-004 idle air spring
06=00 0011  N/A 16022-044-680 valve (slide) set 6a 6b
6a=09 1111  N/A 16141-044-683 throttle valve (slide)
6b=05 1111  N/A 16185-044-004 throttle spring

10=00 0022  .80 00-93500-03008 phillips screw M3 x 8
13=00 0o10N/A 99114-044-0681 main jet 68
13=00 00oN/A 00-99120-06214 main jet 62
14=00 0011  N/A 99203-044-5201 slow jet

Part Sets: Before 1968 most Honda parts were sold individually. That is how the top carb is listed and illustrated. Starting in 1968, many Honda parts were only sold in sets. That is how the bottom carb is listed and illustrated. 

Parts for the top carb that are the same as the bottom, are only listed in the bottom carb parts.

 


2. Keihin
size carb model code eng  years    frame number range      Honda models
0∅9  C4A on #063 ohc 1969-70 PC50-1000000 to 1057917   PC50 xxxxxx40 km/h
∅10  C5A on #063 ohc 1969-70 PC50-1057918 to 1060412   PC50 (1306302) 50 km
∅10  C5A on #063 ohc 1969-70 PC50-1060413 to 0000000   PC50 Little Honda (US)  
∅10  C5A on #064 ohc 1969-70 PS50-1000000 to 1001412   PS50 xxxxxx50 km/h
∅10  S5A on #064 ohc 1969-70 PS50-1001413  to 0000000   PS50 xxxxxx50 km/h
0∅9  C4B on #081 ohv 1970-71 PC50-2000000 to 2039616   PC50K1 xxxx40 km/h
∅10  C5B on #081 ohv 1970-71 PC50-2039617 to 0000000   PC50K1 xxxx50 km/h
∅10  S5B on #082 ohv 1970-71 PS50-2000000  to 0000000   PS50K1 xxxx50 km/h
0∅9  F4A on #081 ohv 1971-73 PC50-0000000 to 0000000   PC50K1 xxxx40 km/h
∅9 o F4A on #099 ohv 1970-73 PF50-1000000 to 0000000   PF50 Amigo  40 km/h
∅10  F5A on #081 ohv 1971-73 PC50-0000000 to 0000000   PC50K1 xxxx50 km/h
∅10  F5A on #099 ohv 1970-73 PF50-1000000 to 0000000   PF50 Amigo  50 km/h

Links to Images:
1969-70 Honda PC50A (USA)     Keihin C5A      1969 Honda PC50A (Euro)
1973 Honda PC50K1  xxxxxxx Keihin F4A

PC50 ohc engine

 

1969-70 PC50: Before April 1970, the PC50 had a OHC engine (over head cam). Bore 42.0 mm, stroke 35.6 mm, displacement 49.3 cc. The valves were operated by a cam in the head, driven by a cam chain.

Spigot mount: The Keihin C4A, C5A, C4B, C5B carburetors for the early 1969-70 PC50A were spigot mount type. They had a round float bowl gasket (with three flat sides when installed), a push-in jet, jet pad, completely round “donut” float, all metal float needle with replaceable float seat.

PC50K1 ohv eng.

1970-73 PC50K1: After April 1970, the PC50K1 had a OHV engine (over head valve). The valves were operated by pushrods from a cam down in the case.

Flange mount: The Keihin F4A, F5A, carburetors for the 1970-73 PC50K1 were flange mount type with 32mm bolt spacing. The intake o-ring 2 x 18 (22 OD) groove was on the intake pipe, rather than the carburetor flange like all future ones. Everything else was the same, round float bowl gasket (with three flat sides when installed), a push-in jet, jet pad, completely round “donut” float, all metal float needle with replaceable float seat.

 

1969 Honda PC50 carburetor illustration

Keihin C4A,B  C5A,B

0o quantity  
o#
⇓⇓⇓⇓⇓⇓ 
Keihin (a)C4A (b)C5A (c)C4B (d)C5B (e)F4A (f)F5A
o# abcdef  price   Honda part#x  description xxx specs
00 100000  N/A 16100-063-690 carb. C4A   ∅9  69-70 PC50
00 010000  N/A 16100-063-004 carb. C5A ∅10  69-70 PC50, PS50

00 001000  N/A 16100-081-690 carb. C4B   ∅9  70 PC50K1 < 2039617
00 000100  N/A 16100-081-014 carb. C5B ∅10  70 PC50K1 > 2039616

00 000010  N/A 16100-099-690 carb. F4A   ∅9  70-73 PC50K1, PF50
00 000001  N/A 16100-099-600 carb. F5A 10  70-73 PC50K1, PF50
01 111011 $17 16010-063-004
gasket solo-set 1d 1e 1n 1p 1q
01 000100 $17
16010-063-000 gasket solo-set 1d 1e 1n 1p oo 1r
0
1 111111 $18 16010-114-305 gasket multi-set 1d 1e 1n 1p 1q 1r
1d 111111 0$2 16176-551-004 main jet o-ring 1 x 3 (5 od)
1e 111111 $10
16197-063-004 jet pad disk Ø7.3 x 1.9

1n 111111 0$7 16173-063-004 float bowl o-ring 1.5 x 40 (43 od)

1p 111111 0$5
 16171-044-004 top rubber washer 10 x 15 x 1
1q 111011 0$3 16189-056-004 drain screw seal washer 3 x 6 x 0.5
1r  000100 0$5 16175-001-004 drain screw o-ring C5B 2 x 4 (8od)

02 00110N/A 16012-064-004 needle set F5A 2a 2c 2d 2f

2a 
11110N/A 16051-063-004 jet needle C4A C5A C4B C5B F5A
2b 000010  N/A 16051-063-690 jet needle F4A
2c
111111 0$5 16156-044-004 needle w-clip
2d
111111 0$2 16157-044-004 needle e-clip 1.5 for 2.0 needle
2e
110000  N/A 16133-063-004 needle jet C4A C5A 2.1 x 2.5
2f  00110N/A 16133-081-004 needle jet C4B C5B F5A
2g 000010  N/A 16133-081-690 needle jet F4A

03 111111  N/A 16013-064-004 float set 3a 3b 3c 3d 3e 10
3a 111111  $13 16123-063-004 float needle (all metal)
3b 111111  N/A 16122-063-004 float
3c 111111  N/A 16127-063-014 float arm
3d 111111  N/A 16126-063-014 float hinge pin
3e 111111  N/A 16196-063-014 float pin plate
04 111111  N/A 16014-064-004 top set 4a 4b 1p
4a 111111  N/A 16119-063-004 top with pipe

4b 111111  N/A 16118-045-004 cable adjuster female M6-0.75
05 111011  N/A 16015-064-004 chamber set 5a 5c 1n 1q
05 000100  N/A 00000-000-000 chamber set 5b 5d 1n 1r
5a 111011  N/A (not sold separately) chamber bare
5b 000100  N/A (not sold separately) chamber bare
5c 111011  N/A 16164-225-004 drain screw C4A C5A C4B F4A F5A
5d 000100  N/A 16162-304-004 drain screw C5B
06 111111  N/A 16016-063-004 adjustment screw set

6a 111111  N/A 16163-063-014 idle speed screw
6b 111111  N/A 16162-044-004 idle air screw & spring
6c 111111  N/A 16181-250-004 idle speed spring
07 111111  N/A 16022-063-004 throttle valve set
7a
111111  N/A 16141-063-004 throttle valve (slide)
7b 111111  N/A 16185-044-004 throttle spring
09 111111  N/A 16194-063-004 cable pipe cover
10 222222 $1.00 93500-0300500A phillips screw M3 x 5
11 222222 $1.00 93500-040120A phillips screw M4 x 12
12 111111 $0.50 94111-030000 spring washer M3
13 222222 $0.20 94111-04000 spring washer M4 
15 101010  N/A 99201-063-0550 main jet #55 push-in see jets below
15 01010 N/A 99201-063-0620 main jet #62 push-in see jets below
18 111111  N/A (not sold separately) idle jet press-in tube 0.35=0.0138″ 

 

 


1975 PF50

3. Keihin
size   carb   years  model code      models00xxxxxxxspeed version
0∅9 PA 01A on 1973-77 081 Honda PC50K1 00xxxxxxx  40 km/h
0∅9 PA 01A on 1973-78 099 Honda PF50R Amigo/Novio 40 km/h
∅10 PA 00A on 1973-77 081 Honda PC50K1 00xxxxxxx  50 km/h
∅10 PA 00A on 1973-78 099 Honda PF50R Amigo/Novio 50 km/h
∅10 PA M0A on 1978-83 000 Indian AMI-50 (US) xxxxx   30 mph

Links to Images:
Honda PC50K1 carburetor Keihin PA 00A-A      Honda PC50K1 carburetor
Honda PC50K1 float bowl missing the rubber disk (push-in jet support pad)
1975 Honda PC50K1    
1980 Indian AMI50        Indian AMI50 carburetor Keihin PA M0A-A

Late PC50: The carburetor changed from “donut” float to a swinging float, and a NC50-type float bowl and gasket. The 1973-77 PC50K1 and 1973-78 PF50 engine and carb are the same as the Taiwan remake engine and Keihin carburetor used on the 1978-83 Indian moped. So the carburetor parts are the same also, with some exceptions.

PA 00A (16100-081-024) and PA 01A (16100-099-693) have the same parts. The push-in jet size, venturi size and intake flange o-ring are the only difference. Here is the cmsnl.com carburetor parts list for PA 00A and 01A on Honda PF50 Amigo (NE, BE, FR, DE, IT, UK) model. It is the main source of the information below.

1980 Indian AMI-50

PA M0A (E210-20-50) has the same parts as PA 00A and PA 01A, but has a screw-in jet instead of push-in. So the jet, jet pad, jet o-ring, and float bowl are different. 

Flange Mount: 32 mm hole spacing, 2 x 18 (22 od) o-ring 00A, 01A.

Indian AMI50: The Indian AMI50 Chief four stroke moped engine, OHV with pushrods and internal pedals, made from 1978-1984, is a Taiwan-made copy of a Honda PC50K1 or PF50 engine, OHV with pushrods and internal pedals, made from 1973-1978. The Indian had three different carburetors, Tillotson (some 1978), Keihin (some 1978, most 1979-80), Mikuni (some 1980, all 1981-84). Only the Keihin parts are listed here.

 

Keihin PA 00A 01A M0A

 quantity
o#
⇓⇓⇓   
Keihin  (a)PA-00A  (b)PA-01A  (c)PA-M0A
o# abc price Indian part#  Honda part#x  description xxx specs
00 1oo  N/A E210-00-00 16100-081-024 carburetor PA 00A Ø10 E10
00 o1o  N/A E210-00-00
16100-099-693 carburetor PA 01A   Ø9 E10
00 oo1  N/A E210-00-50 16100-000-000 carburetor PA M0A Ø10
o1 11o $22 E231-00-00
16010-081-004 gasket solo-set   1a o d e f o h i
o1 110 $23 E231-00-00 16010-143-305 gasket multi-set 1a c d e f o h i

o1 oo1 $18 
E231-gask   16010-081-014 gasket solo-set  1a o o o f g h
o1
001 $19 E231-00-00 16010-181-305 gasket multi-set 1a o o o f g h i  l

1a 111 $$3 E231-####00000-000-000 top rubber washer 10 x 18 x 1
1c 000 $$2 E231-00-00 00000-000-000 intake o-ring 2 x 20 (24 od) 
1d 11o 0$2 0000-00-00 16176-551-004 main jet o-ring 1 x 3 (5 od)

1e 11o $10 E231-00-00 16197-063-004 jet pad disk Ø7.5 x 1.8 

1f  111 $15 E231-02-00 00000-000-000 float bowl gasket Ø1.5 NC50-type
1g oo1 $$2 E231-11-00 00000-000-000 drain screw o-ring 1.5 x 4 (7 od)
1h 11o $$2 0000-00-00 00000-000-000 intake o-ring 2 x 18 (22 od)

1i 110 0$2 0000-00-00 16175-260-004 drain screw o-ring 2 x 2.5 (6.5 od)

02 111 $24 E231-13-00 16155-883-005 float needle valve non-stirrup type
03 111  N/A E231-####16012-081-014 needle set 3a 3b 3c 3d
3a 111 $10 E231-09-00 00000-000-000 jet needle D348 thick Ø2 x 33
3b 111 0$2 E231-10-00 16157-044-004 needle e-clip substitute 1.5mm
3c 111 0$5 E231-08-00 16156-044-004 w-spring clip

3d 111N/A E231-####16133-081-004 needle jet ∅3.95 ∅5 ∅3.9 ∅5 x 27
3d ooo $$6 E231-00-00 16133-000 03A needle jet ∅3.95 ∅5 ∅3.9 ∅5 x 27
3d ooo $$6 E231-00-00 16133-000 03B needle jet ∅3.95 ∅5 ∅3.9 ∅5 x 27
o4 111 $28
 E231-####16013-147-004 float set 4a 4b 4c
4a 111 $21 E231-06-00 00000-000-000 float bare white non-stirrup
4b 111 $$4 E231-15-00 00000-000-000 hinge pin substitute Ø2 x 18.5
4c 111 $$3 E231-16-00 0-93600-04006 hinge pin screw M4 x 6 sunk
05 111 N/A E231-01-00 16014-081-004 top set 5a 5b 1a

5a 111 $25 E231-03-00 00000-000-000 substitute cap brass M20-1.0 
5b 111 $$3 E231-####00000-000-000 cable adjuster male M6-0.75

06 11oN/A E231-01-00
16015-081-004 chamber set 6a 6b 1f 1i
6a 11oN/A 0000-00-00 16015-165-B10 float bowl bare for push-in jet
06 oo1 $67 E231-####
16015-099-601 chamber set 6a 6c 1f 1g
6a oo1 $46 E231-01-00 16015-165-B10 float bowl bare for screw-in jet
6b 
11o  N/A E231-00-00 00000-000-000 bowl drain screw M4-0.70

6c oo1 $16 E231-23-00 00000-000-000 bowl drain screw M6-1.00
07 111 $15 E231-####16016-143-620 adjustment screw set 7a 7b 7c 7d
7a 111 $$6 E231-19-00 00000-000-000 idle air mix screw M6-0.75 special
7b 111 $$4 E231-21-00 00000-000-000 idle speed screw M4-0.70 special
7c 111 $$5 E231-20-00 00000-000-000 idle air screw spring Ø5.6 x 10
7d 111 $$2 E231-22-00 00000-000-000 idle speed screw spring Ø4.9 x 9
08 1o1 $40 E231-####16022-081-004 valve set 8a 8b Ø13 PA 00A
08 1o1 $00 E231-####16022-HB2-003 new #

8a
1o1 $25 E231-07-00 00000-000-000 throttle slide Ø13 #15A PA 00A
8b 1o1 $15 E231-17-00 00000-000-000 throttle spring Ø10 x 42 PA 00A
08 o1o  N/A 0000-00-00 16022-143-620 valve set 8a 8b Ø12 PA 01A
08 1o1 $00 E231-####16022-191-004 new #

11 111 $2.00 E231-04-00 16118-086-004 rubber boot substitute Dellorto
12 222 $1.00 E231-12-00  93500 – 04012 bowl screw M4 x 12 pan phillips
13 222 $0.25 E231-####   95002-02070 bowl screw lock washer
14 111N/A    E231-####   95001-35150
drain hose
15 111N/A    E231-####0-95002-02070 drain hose clamp
16 oo1 $$7 E231-18-00 99101-187-070 main jet #70 M6-0.75 screw-in
16 oo1  N/A E231-00-0 99201-187-0700 new #

16 11o $16 E231-00-00 99201-081-070 main jet
#70 0.0275″ push-in
16 11 N/A E231-00-0 99201-081-0700 new #

17 oo1N/A E231-01-00 00000-000-000 carb body bare
18 oo1N/A E231-####00000-000-000 idle jet press-in tube 0.38 mm=0.015″ 

Indian PA-MOA carb disassembled

 

Choke plate: These three carbs have a lever choke that swings a plate to block air flow. There is no enrichment fuel path or jet. So the float bowl has no choke jet. The other baby Keihins with cable or vacuum operated choke do have a choke jets in their float bowls. The choke (enrichment) fuel passes up through the sealed off corner of the bowl gasket.  

Float Bowl: The PA-03A and 03B chamber set (float bowl, float bowl gasket, drain screw and drain screw o-ring) from 1970’s Honda mini-cycles (Mini Trail or Monkey) interchanges with a PA 00A, 01A chamber set  from 1970’s Honda mopeds. The drain screw (4 or 6 mm) and its o-ring (2×2.5 or 1.5×4) are different. So if the float bowl is changed the drain screw must also be changed. 

Needle jet: The PA-03A and 03B mini-cycle needle jets (emulsion tubes) interchange with PA 00A, 01A, and M0A moped ones. These press out with taps from a hammer and punch from above. At first the punch tip needs to be bigger than the 4 mm tube end. Once the tube end gets below the floor a smaller 3.5 to 3.9 mm straight round bar is needed. It has to enter the 4 mm hole and contact the idle tube around the edge.

Keihin MOA parts

Idle jet: A little downstream from the needle jet is the idle jet. It is a pinhole 0.015″ at the upper end of a vertical brass tube about 20mm long. The idle tube is a press fit in the carb body. Some can be pulled out with just a pliers. Some might be tighter and require a drill bit be placed inside the tube to prevent crushing from the tighter pliers grip. This tube was never intended to be replaced and is not sold or included in any common carb kit. 

Air tunnels: In the front below the main air inlet are two small horizontal air tunnels. The center tunnel is main air and the side tunnel is idle air. The small amount of air sucked in through the main air tunnel passes through tiny holes in the emulsion tube and becomes thousands of microscopic air bubbles in the liquid gasoline that is being drawn upward. The tiny amount of air sucked in through the idle air tunnel passes around the idle air adjustment screw cone shape tip and goes to the vertical idle passage just above the idle jet. The idle air tunnel is the size of a regular paper clip 0.036 inch. A straightened paper clip cleans it perfectly.    

 


4. Keihin
∅10 BB 21A-B,F 148 on 1978-79 Honda PA50 I   Hobbit (US) 20 mph
∅12 BB 20A-C  #148 on 1978-83 Honda PA50 II Hobbit (US) 30 mph

Links to Images:
1978 Honda PA50 II (USA 30mph)

Flange mount: 42 mm bolt hole spacing

Honda’s successor to the four-stroke PC50 was the two-stroke PA50, known in the USA as Hobbit, and in Europe as Camino. It was made in Belgium by Honda Benelux, so it had a mix of Japanese and European design and componentry. 

In US models, 20 mph versions were 1978-79 red. 30 mph versions were 1978-79 yellow, 1980 yellow, 1981-82 red, and 1983 black.

This Keihin BB type carburetor is not like any other moped carburetor. It looks more like a Honda generator carburetor. It is a very flat design. It has to be special because it swings up and down with the engine, and is very close to the frame at the place where you step through.   

Keihin (1978-83 Honda PA50) carburetor illustration

Keihin BB-20A and BB-21A

  quantity
o#
⇓⇓   
Keihin  (a)BB 21A-B or F   (b)BB 20A-C 
o# ab price  Honda part# x description xxx specs
00 1o  N/A 16100-148-645

00 1o  N/A 16100-148-646 carburetor 21A ∅10 (20 mph ’78-79)
00 o1  N/A 16100-148-708 carburetor 20A ∅12 (30 mph ’78-83)
01 11 $14 16010-124-760 gasket solo-set   1c 1g oo 1j
01 11 $15 16010-156-305 gasket multi-set 1c 1g 1h 1j

1c 11 $$2 00000-000-000 intake o-ring 2 x 20 (24 od)
1g 11 $$2 00000-000-000 drain screw o-ring 1.5 x 4 (7 od)

1j  11 $11 00000-000-000 float bowl gasket 2 x 50 (54 od)
o2 11  N/A 16011-147-004 16011-147-305
o2 11 $21 16011-881-741 float needle valve stirrup type

03 11  N/A 16013-124-760
03 11  N/A 16013-124-762 float set 3a 3b
3a 11  N/A 00000-000-000 float bare
3b 11  N/A 00000-000-000 hinge pin

04 11  N/A 16016-148-611 screw set 4a 4b 4c 4d 4e
4a 11 0$1 00000-000-000 idle speed screw M4 x 15 slot
4b 11  N/A 00000-000-000 idle speed spring
4c 11  N/A 00000-000-000 idle fuel screw
4d 11  N/A 00000-000-000 idle fuel spring
4e 11 0$3 00000-000-000 cleaning access plug M5 x 5 slot
05 11  N/A 16024-124-760 drain screw set
07 11  N/A 16110-148-010 choke lever cover
08 11  N/A 16166-148-740 nozzle, main
09 11  N/A 16199-148-611 vent hose ∅3.5 ∅6.5 x 65 gray
09 11 
.50 16199-148-sub substitute∅3.1 ∅6.3 x 65 clear
10 11 0$2 0-93500-04008 cable pinch screw M4 x 8
11 22 0$1 0-93500-04012 bowl screw M4x12 pan phillips
12 22  .50 0-94111-04800 lock washer M4 split
13 11 N/A95001-35400-40 drain hose ∅3.5 ∅7.0 x 400 gray

13 11  $1 95001-35400sub substitute ∅3.1 ∅6.3 x 400 clear
14 10  N/A 99101-124-600 main jet 60 21A
14 0 N/A 99101-124-780 main jet 78 20A

15 11  N/A 0-95002-02070 drain hose clamp B7 (for 7 not 6.3)
16 11  N/A 0-95002-02065 vent hose clamp B6.5

 

1978 PA50 carb service

PA50 carb removal

 Servicing: The best way to remove the PA50 carburetor is to hold the back of the bike up by either a rope tied to an overhead beam, or with a milk crate and blocks of wood. Remove the floorboards and side covers. Unplug the ignition wires from the coil at the right rear. Pull them through and move them out of the way. Disconnect the decompression cable and the spark plug cap. Loosen the wiring clamps so there is slack in the wires. Remove the lower rear shock bolts and the swing arm pivot bolt above the engine. Then the whole sub-frame can be moved away from the main frame, either by lifting the back of the bike up, or by swinging it around sideways.

Note that the float bowl can go on two different ways. The wrong way assembles normally, but causes the vertical brass overflow tube to contact the float. Honda designed all of the cleaning ports, drain screws, and adjustment screws to face the right side of the bike, which is the upper left in the exploded view. The drain hose spigot on the float bowl faces the same way as the adjustment screws. The other way to tell is by shaking the carburetor. If you can hear the float rattling inside then the float is not stuck so the float bowl is on correctly. 

While every other moped carburetor is a sliding throttle valve type, this one is a swinging plate throttle valve. The reason is to be flatter, to get more clearance from the bottom of the frame. The manual choke is also a swinging plate, with an automatic release.

Some servicing can be done with the carburetor installed. It is easy to clean the idle passages and jet by spraying a one second long burst of carb spray into the idle mixture screw hole, followed by compressed air. The running engine is allowed to consume the flammable solvent before the next burst is sprayed in, to prevent the engine from getting flooded.

 

 


1975 PF50M

5. Keihin
size carb model code years       Honda models
∅12   006A on #131 1974-75 MR50 Elsinore (US)
∅10 PA06A on #122 1973-75 PM50 Canguro, PM50 Novio  40 km/h
∅10 PA07A on #143 1975-78 PF50M, PF50MR (BE,NL,NZ) 40 km/h
∅12 PA07A on #143 1975-78 PF50M, PF50MR (FR,UK,CA) 50 km/h

Links to Images:
Keihin PA06B carburetor     Keihin PA07A carburetor    Keihin 006A carburetor
1973 Honda PM50 Canguro      1974 Honda PM50 Novio

Flange mount: PA06A PA07A 32 mm bolt hole spacing
Spigot-mount: 006A

Cable-choke: The choke cable passes through the carb top along with the throttle cable.  

Keihin PA06A-A and PA07A-A

  quantity
o#
⇓⇓⇓   
Keihin    (a)006A   (b)PA06A   (c)PA07A
o# abc price  Honda part# x description xxx specs 
00 10o  N/A 16100-131-004 carburetor ∅12 006A   74-75 MR50

00 o00  N/A 16100-122-004 
00 o00  N/A 16100-122-014 carburetor ∅10 696A
00 o00  N/A 16100-122-024 carburetor ∅10 PA06B

00 01o  N/A 16100-122-690 carburetor ∅10 PA06A PM50 < 20101

00 01o  N/A 16100-122-691 carburetor ∅10 PA06A PM50 > 20100
00 01o  N/A 16100-122-692 carburetor ∅10 PA06A PM50 > 20100 

00 o01  N/A 16100-143-620 carburetor ∅12 PA07A PF50M, PF50MR
00 10o  N/A 16010-131-004 gasket solo-set   5-piece 1a d e f o i

01 011  N/A 16010-122-004
01 011  N/A 16010-122-014 gasket solo-set   7-piece 1a d e f h i s
01 111  N/A 16010-122-305 gasket multi-set 7-piece 1a d e f h i s
1a 111 
N/A 00000-000-000 top gasket Ø1.5
1d 111 0$2 16176-551-004 main jet o-ring 1 x 3 (5 od)
1e 111 $10 16197-063-004 jet pad disk Ø7.5 x 1.8 

1f 111  N/A 00000-000-000 float bowl gasket Ø1.5
1h 011 $$2 00000-000-000 intake o-ring 2 x 18 (22 od)

1i  111 0$2 16175-260-004 drain screw o-ring 2×2.5(6.5od)
1s 111  N/A 00000-000-000 float valve o-ring 1.5 x 5 (8od)
96 011  N/A 99201-1220650 main jet push-in #65 PA06A

96 100  N/A 99201-1220750 main jet push-in #75 006A PA07A?

 

 

 


6. Keihin
size     carb  model code  year 00 frame number range  000  model
∅12 PA08B-A or B #147 1977 NC50-1139281 to 0000000 NC50 Express (US)    30 mph
∅12 PA08B-A or B #147 1978 NC50-2000013 to 0000000 NC50 Express (US)    30 mph
∅12 PA08E-A or B #147 1979 NC50-2100011 to 0000000 NC50 Express (US)    30 mph

∅12 PA08E-A or B #147 1980 NC50-2200005 to 0000000 NC50 Express (US)    30 mph
∅12 PA08B-B    on #163 1979 AB01-5000001 to 0000000 NA50 Express II (US) 30 mph

∅12 PA08D-A    on #163 1980 AB01-5200001 to 0000000 NA50 Express II (US) 30 mph

1981 NC50

Links to Images:
Keihin PA08B-A carburetor
1977-79 Honda NC50 with PA08B-A carb 
Keihin PA08E-A carb for 1980 Honda NC50 (missing top cap and cable choke)
Keihin PA08E-B carb for 1980 Honda NC50 Express
Keihin PA08D-A carb for 1980 Honda NA50 Express II

Flange Mount: 38 mm hole spacing. 2 x 20 (24 od) intake o-ring.

Honda Express carburetor versions, showing things that are different.

Honda Express carburetor versions

Cable choke: This carburetor has a throttle cable and a choke cable coming straight up and looping around. It has no vent hoses, vacuum hoses, or oil lines going into it. The oil injection goes into the intake manifold. The float reservoir vent is just a small tube slanting downward.

As with most Honda carburetors, fuel is never allowed to spill onto the engine or anything else. Instead an overflow tube inside the float chamber allows any overflow fuel to flow out and down the drain hose and onto the ground below the engine.  

The 1977-79 Honda NC50 and NA50 each had two carburetor versions, PA08B-A and PA08B-B. Regardless of the year, or the VIN number, they could have either version. So the customer had to look at the model number stamped into the carburetor, and tell the Honda dealer that number, to get certain parts correct. 

Oil injection hose location: The 1977-79 Honda Express had the oil hose going into the intake manifold, not the carburetor. The 1980 and later models had the oil injection hose going into the carburetor at the throttle slide area. There must have been some benefit, like maybe throttle slide lubrication.

PA08B-A and PA08B-B

    quantity
o#
⇓⇓⇓⇓⇓ 
Keihin PA(a)08BA (b)08BB (c)08EA (d)08EB (e)08DA 
o# abcde price  Honda part#x  description xxx specs
10 1ooooN/A 16100-147-673 

10 1ooooN/A 16100-147-675 carburetor 77-78 NC50 PA 08B-A
10 o1oooN/A 16100-147-676 carb 78-79 NC50 NA50 PA 08B-B
10 oo1o0N/A 16100-147-711 carburetor 
1980 NC50 PA 08E-A
10 oo01o  N/A 16100-147-712 carburetor 
1980 NC50 PA 08E-B
10 oooo1N/A 16100-163-771 carburetor  1980 NA50 PA 08D-A

o1 10ooo $23 16010-143-620 gasket solo-set   1a o c d e f g
o1 o1111 $20 16010-147-711 gasket multi-set oo b c d o f g
1a 100o0 $$3 00000-000-000 top rubber washer 10 x 18 x 1
1b o1111 $$8 00000-000-000 top rubber washer 13 x 16.5 x 1
1c 11111 $$2 00000-000-000 intake o-ring 2 x 20 (24 od) 
1d 1o1o1 0$2 16176-551-004 jet or screw o-ring 1 x 3 (5 od)
1e 1oooo $10 16197-063-004 jet support pad disk Ø7.5 x 1.8
1f 11111 $15 00000-000-000 float bowl gasket  Ø1.5 NC50-type
1g 11111 $$2 00000-000-000 drain plug o-ring 1.5 x 4 (7 od)
o2 1oo1o $21 16011-881-741 float needle valve  stirrup
o2 o11o1 $24 16155-883-005 float needle valve regular
o3 1o1o0  N/A 16012-147-004 needle set 3a 3b 3c 3d 08BA EA
o3 ooooo $22 16012-130-640 needle set 3a 3b 3c 3d PA 03A-A
o3 ooooo $22 16012-165-014 needle set 3a 3b 3c 3d PA 03B-A

o3 o1o11 $15 16012-147-014 needle set 3a 3b 3c 08BB EB DA
3a 11111 0$5 16156-044-004 jet needle w-clip
3b 11111 0$2 16157-044-004 jet needle e-clip 1.5 for Ø2.0 needle
3c 11111 $10 00000-000-000 jet needle Ø2.0 D348 thick 08B-A,
3c 11111 $10 00000-000-000 PA 08B-B, 03A-A, 00A, 01A

3c ooooo $10 00000-000-000 jet needle Ø2.0 D117 thin 03B-A,
3c ooooo $10 00000-000-000 PA 03C-A, 03D-A, 03H-B, 03M-A, etc
3d 1o1oo  N/A 00000-000-000 needle jet (emulsion tube) 08BA 08EA
3d o1o11  N/A 00000-000-000 needle jet & jet fixed 08BB 08EB 08DA

3d ooooo $10 00000-000-000 needle jet (emulsion tube) PA 03A-A
3d ooooo $10 00000-000-000 needle jet (emulsion tube) PA 03B-A
o
4 1oo1o  N/A 16013-143-620
o4 1oo1o  N/A 16013-099-691 float set 4a oo 4c 4d black stirrup
o4 o11o1 $28 16013-147-004 float set oo 4b 4c 4d white regular
4a 1oo1o  N/A 00000-000-000 float bare, solid black foam stirrup
4b o11o1 $21 00000-000-000 float bare hollow white plastic regular
4c 11111 $$4 00000-000-000 hinge pin substitute Ø2 x 18.5
4d 11111 $$3 0-93600-04006 hinge screw M4x6 sunk phillips

1977-79 NC50 idle adjustment screws
7a idle speed screw, tighter is faster
7c idle air mix screw, tighter is richer

o5 1oooo $25 16014-143-620 top set substitute 5a 1a M20-1.0
o5 o1111 $22 16014-147-004 top set substitute 5a 1b M18-1.0
o6 1ooooN/A 16015-147-004 chamber set A 6a oo 6c 1e 1f 1g for jet pad
o6 o1111  N/A 16015-147-014 chamber set B  oo 6b 6c oo 1f 1g for no pad
6a 1oo0oN/A 16015-147-004 float bowl A shallow with pad holder
6b o1111  N/A 16015-147-014 float bowl B shallow, no jet pad holder
6c 11111 $16 00000-000-000 float drain screw M6x20 special
o7 11o1o $15 16016-143-620 screw set 7a b c d idle air
o
7 oo101  N/A 16016-147-711 screw set 7a b o d e f g idle fuel

7a 11111 $$4 00000-000-000 idle speed screw M4x19 special
7b 11111 $$2 00000-000-000 idle speed screw spring Ø5.6 x 10
7c 11o1o $$6 00000-000-000 idle air screw M6-0.75 thick tip
7d 11111 $$5 00000-000-000 idle air or fuel spring Ø4.8 x 9
7e oo1o1  N/A 00000-000-000 idle fuel screw M6-0.75 thin tip
7f  oo1o1 $$3 00000-000-000 idle fuel screw washer 3.1 x 5.0 x 0.5
7g oo1o1 0$2 16176-551-004 idle fuel screw o-ring 1 x 3 (5 od)

1980-83 NC50 idle adjustment screws
7a idle speed screw, tighter is faster 
7e idle fuel mix screw, tighter is leaner

o8 11111 $38 16022-143-620 valve set 8a, 8b
8a 11111 $25 00000-000-000 throttle slide Ø13 #15A
8b 11111 $15 00000-000-000 throttle spring original Ø9.5 x 42
8b
11111 $$7 00000-000-000 throttle spring substitute shorter, stiffer
o9 11111 $25 16046-147-004 choke set substitute 9a 9b 9c
9a 11111 $10 00000-000-000 choke top substitute plastic M12-1.0
9a 11111 $15 00000-000-000 choke top substitute metal M12-1.0
9b 11111 $$4 00000-000-000 choke spring substitute
9c 11111 $12 00000-000-000 choke slide substitute
11 11111 $2.00 16118-166-004 rubber boot substitute Dellorto
12 22222 $1.00   93500-04012 bowl screw M4x12 pan phillips
13 22222 $0.20   94111-04000 lock washer M4 split
14 11111 $1.00 95001 – 35003 hose substitute 1/8 x ¼ 3.1 x 6.3

1977-80 NC50 cable choke top substitute

15 11111  N/A 95002 – 02070 drain hose clamp B7 (for 7 not 6.3)
16 10o0o  
N/A 99201.081.0780 push-in jet 78 08BA

16 10o0o $23 substitute jet, #70 drilled to 78 08BA
16 01111 N/A fixed needle jet & jet pressed in 08BB EA EB DA
this jet is 0.78mm 0.0307″, cleaned with a #69 drill 0.0292″     

 

Main Jet: On PA08BB, EA, EB and DA versions the main jet is a tamper-proof tight press-fit type, in the center. The jet cannot be removed, and cannot be replaced. It is 0.78 mm – 0.0307″, and can be cleaned perfectly with a #69 drill 0.0292″.    

On a PA08BA the main jet presses or slides in and out, and is supported by a rubber disk. If the disk is missing, the jet can slide downward, allowing fuel to get past the jet o-ring, causing a rich fuel mixture.

Idle Hole Cleaning: Near the engine side of the carb body is a brass tube that dips down into the liquid gasoline. That tube, about 1.5 mm (0.060″) inner diameter and 20mm long, leads to the idle or pilot jet, which is about 0.30 mm (0.012″). The idle jet gets clogged from sitting, then the engine will run but won’t idle. Nothing but a very thin (0.010″) steel guitar string will clean it out. See below about jet drills and cleaning tiny jets. Ultrasonic parts cleaners, carb spray, carb dip, and compressed air are not usually effective. Another way to clean out the idle jet is to 1) place a drill bit that fills the hole (so it does not get crushed), 2) clamp it with a small vise grips, 3) rotate back and forth while pulling, 4) when it comes out, the actual hole is easy to see and clean, 5) press it back in the same way it came out.

Strong solvent is needed to dissolve varnish or tar residue left from years of sitting. Carburetor spray, parts dip, or acetone all help clean out the tar, sometimes with a lot of scraping, brushing or rubbing. Always remember to remove all rubber things first, to not let the rubber touch the solvent. Strong solvents will swell soft rubber, deforming it. Never soak the whole carburetor in strong solvent. In this way, Shaun (at Royal Cyclery and later at Myrons Mopeds) has successfully cleaned out over 100 Honda Express carburetors, without ever replacing any of the rubber gaskets. Part of the reason was they were only sold at Honda dealers, but nonetheless, they are not needed in a normal service or clean-out.

Keihin PA08C-A: This is approximately for a 1979-80 NC50, or maybe NA50. It is identical to a PA08B-B. It has the same white float, non-stirrup float needle, fixed jet, 18mm top threads, and same gaskets. The idle mixture screw type is unknown. No photo available. 

 


7. Keihin
size  carb  model code  years       models
∅12 PA15A-A on #190 1981-81 Honda NC50 Express (US) xxxxx xxxx 30 mph
∅12 PA16A-A on #193 1981-81 Honda NA50 Express II (US) xxxx xxx  30 mph

∅12 PA13B-A on #187 1981-82 Honda NX50 Express SR (US) xxxx xx  30 mph
∅12 PA13B-B on #GA6 1982-83 Honda NC50 Express (US) xxxxx xoxx 30 mph

∅12 PA13E-A on #GC1 1982-83 Honda NU50 Urban Express (US) xxxx 30 mph

∅12 PA13E-A on #GC1 1982-83 Honda NU50M Urb. Expr. Deluxe (US) 30 mph
∅11 PA25A-A on #GA6 1982-83 Honda NC50I Express (Iowa) xxxxxxx25 mph
∅11 PA?????   on #GC1 1982-83 Honda NU50I Urban Express (Iowa) x  25 mph
∅10? PA25A-A on#GC1 1982-83 Honda NU50MI Urb. Ex. Deluxe (Iowa)25 mph

Links to Images:
1981 Honda NC50 Express (1-speed) xxx Keihin PA15A-A carb for 1981 NC50
1981 Honda NA50 Express II (2-speed)   Keihin PA16A-A carb for 1981 NA50
1982 Honda NU50 Urban Express  xxxx  Keihin PA13E-A and Keihin PA13B-B 
1982 Honda NX50 Express SR  xxxxxxx  Keihin PA13B-A carb
1982-83 Honda NC50, NU50 hoses  xxx
 Keihin PA25A-A carb for 1982 NC50I

Flange Mount: 38 mm hole spacing, 2 x 20 (24 od) o-ring on NC50, NA50 (PA15A-A, PA16A-A, PA13B-B)
Flange Mount: 32 mm stud spacing, 2 x 18 (22 od) o-ring on NX50, NU50, NU50M (PA13B-A, PA13E-A)
Flange Mount: 36 mm hole spacing, 2 x 20 (24 od) o-ring on NC50I, (PA25A-A)

Vacuum-operated automatic choke: These carburetors features a screw-in main jet, and a built-in vacuum-operated (not electric) automatic choke. When the temperature switch on the head is cold, it allows the engine vacuum to raise the choke plunger up, which opens a new fuel passage, to enrich the mixture during cold starting. As the engine warms up, it closes the vacuum, allowing the thin spring to pull it back down, for normal running. The more precise term for this is “automatic vacuum operated cold start fuel mixture enrichment device”. The 1981-83 automatic choke device itself is not replaceable.

The vacuum source hose has a check ball valve that only allows air flow into the carburetor venturi, and not back out. It needs this even though there is reed valve, because there is still some residual reverse flow caused by the forward and reverse motion of the piston.

The vacuum choke that came out in 1981 did not last long. After 1983, 50cc on-road Honda’s had electric chokes, because they were electric-start scooters with 12 volt batteries. 

Identical twins: The PA16A-A looks identical to the PA15A-A. It is on the 1981 Honda NA50 Express II, the final year of that USA-only model. They both have 38 mm flange hole spacing, #75 screw-in jet, 20 mm intake o-ring and the non-stirrup type B float needle. The only difference is the top cable curved pipe. On a PA15A-A it is permanently attached to the screw-on top cap with a swivel joint, while on a PA16A-A the curved cable pipe is detachable.

Intake studs: After 1981 these carbs had studs instead of threaded holes in the mounting flange, except for PA25A-A. PA13B-A and PA13E-A studs are spaced 32 mm with a 18mm intake o-ring. PA13B-B studs are spaced 38 mm, with a intake o-ring 20 mm. 

Iowa carb: The PA25A-A is like a PA13B-A, with M18-1.0 top cap threads, vacuum-operated automatic choke, choke jet in float bowl, tall 2.5 x 1.5 float bowl gasket, non-stirrup type float and float needle, screw-in main jet size 75. The only noticeable difference is the absence of studs.

Iowa cylinder: The exhaust port is restricted. Here left is 49-state, right is Iowa.

Keihin PA 15AA 16AA 13BA 13BB 13EA

      quantity
o#
⇓⇓⇓⇓⇓⇓ 
PA (a)15AA (b)16AA (c)13BA (d)13BB (e)25AA (f)13EA
o# abcdef price  Honda part#x  description xxx specs
00 1o0000 N/A 16100-190-672 carburetor ’81-81 NC50 PA15A-A
00 o10000 N/A 16100-193-672 carburetor ’81-81 NA50 PA16A-A
00 o01000 N/A 16100-187-673
carburetor ’81-82 NX50 PA13B-A
00 o00100 N/A 16100-GA6-671 carburetor ’82-83 NC50 PA13B-B
00 o00010 N/A 16100-000-000 carburetor ’82-83 NC50I PA25A-A

00 o0000
N/A 16100-GC1-671
carburetor ’82-83 NU50 PA13E-A
01 001
001 $24 16010-187-003 gasket solo-set   1b o d g h k
01 110110 $24 16010-190-004 gasket solo-set   1b c d g o k
01 001001 $25 16010-GF8-305 gasket multi-set 1b o d g h k t u

1b 111111 $$8 00000-000-000 top rubber washer 13 x 16.5 x 1
1c 110110 $$2 00000-000-000 intake o-ring 2 x 20 (24 od) 
1d 111111 0$2 16176-551-004 idle fuel screw o-ring 1 x 3 (5 od)
1g 111111 $$2 00000-000-000 drain plug o-ring 1.5 x 4 (7 od)

1h 001001 $$2 00000-000-000 intake o-ring 2 x 18 (22 od)
1k 111111 $22 00000-000-000 float bowl gasket 2.5 tall by 1.5 wide
02 0010?0  N/A 16012-187-671 needle set 2a 2b

02 1100?0  N/A 16012-193-671 needle set 2a 2b 2c 2d
02 0001?1  N/A 16012-GA6-671 needle set 2a 2b 2c oo 2e

02 0000?1  N/A 16012-GC1-671 needle set 2a 2b 2c oo 2f

2a 111111 0$5 16156-044-004 jet needle w-clip
2b 111111 0$2 16157-044-004 jet needle e-clip for 1.5 clip groove
03 111111 $28 16013-147-004 float set white 3a 3b 3c
3a 111111 $21 00000-000-000 float bare white plastic regular
3b 111111 $$4 00000-000-000 hinge pin substitute Ø2 x 18.5
3c 111111 $$3 0-93600-04006 hinge screw M4x6 sunk phillips
04 1o0000  N/A 16014-190-014 top set NC50 fixed cable pipe M18-1.0
04 o10000 $24 16014-147-014 top set NA50 detachable pipe M18-1.0
04 o01110  N/A 16014-187-013 top set NX50, 82-83 NC50 M18-1.0

04 o00001  N/A 16014-GB2-003
04 o00001  N/A 16014-GB0-831 

04 o00001  N/A 16014-098-980 top set NU50 fixed cable pipe M18-1.0

05 110000  N/A 16015-191-034 chamber set deep bowl with choke jet
05 001000  N/A 16015-187-671 chamber set deep bowl with choke jet
05 0001?0  N/A 16015-GA6-671 chamber set deep bowl with choke jet

05 0000
?N/A 16015-187-043 chamber set deep bowl with choke jet
06 000111 $22 16016-191-004 idle fuel adjustment screw set
06 111000 $22 16016-187-003 idle fuel adjustment screw set

6e 111000  N/A 00000-000-000 idle fuel mixture screw M6-0.75 special
6b 111111 $$5 00000-000-000 idle fuel mix screw spring Ø5 x 9
6f  111111 $$3 00000-000-000 idle fuel mix screw washer 3.1×5.0x0.5
07 111111 $0016028-187-003
07 111111 $15 16028-GC8-004 idle speed screw and spring 7a 7b

7a 111111 $$4 00000-000-000 idle speed screw M4x19 special
7b 111111 $$2 00000-000-000 idle speed screw spring Ø5.5×10
08 1100?0 $38 16022-143-620 throttle slide & spring
08 0010?1  N/A 16022-187-731 throttle slide & spring
08 0001?1 
N/A 16022-191-004 throttle slide & spring
8a 110000 $25 00000-000-000 throttle slide Ø13 #15A
8b 110000 $15 00000-000-000 throttle slide spring Ø9.5 x 42

Keihin PA15 idle fuel mixture screw

10 100000  N/A 16118-086-004
10 100000  N/A 16118-166-004 cable rubber boot
10 101110  N/A 16118-187-003 cable rubber boot
10 00000N/A 16118-GB4-003 cable rubber boot

11 111111 $24 16155-883-005 float needle valve KL 18-4608
12 110110  N/A 16199-435-771 overflow hose 3.0 x 6.5
12 00100N/A 16199-187-003 
12 00100N/A 16198-HC0-405 overflow hose 3.0 x 6.5
13 001000  N/A 16608-187-000 control hose with check ball 5 x 10

13 110000  N/A 16608-193-670 control hose with check ball 5 x 10
13 000110  N/A 16608-GA6-670 control hose with check ball 5 x 8

13 00000N/A 16608-GC1-000 control hose with check ball 5 x 8

14 222222 0$1 93892-04012-08 screw & washer M4x12 pan phillips
15 111111  N/A 95002 – 02070   hose clamp B7 vacuum source hose
16 111000  N/A 95002 – 02100   hose clamp B10 for control hose
16 000111  N/A 95002 – 02080   hose clamp B8 for control hose

17 111111  N/A 95002 – 02650   hose clamp B6.5 for overflow hose
18 111111  N/A
 95005 – 35001   vacuum (source) hose 3.5 x 7 x 130
19 oo0010 $$7 99101-187-0700 screw-in jet #70 M6-0.75 PAMOA PA25A ? 78-80 Indian, 82-83 NC50I
19 110100 0$7 99101-187-0750 screw-in jet #75 M6-0.75 PA15A 16A 13BB 81-83 NC50, 81 NA50
19 oo1000 0$7 99101-187-0780 screw-in jet #78 M6-0.75 PA13BA 81-82 NX50
19 oo0001 0$7 
99101-187-0850 screw-in jet #85 M6-0.75 PA13EA 82-83 NU50

 

 

Float Valve Seat: On these carburetors the float seat (the cup that the float needle valve slides in) is carved into the actual carburetor body, and is not replaceable. Polish it with a spinning Q-tip and polish, such as Turtle Wax. 

Choke jet: On all of these NC50-type carbs, both shallow and deep-float-bowl versions, there is a choke jet, pressed into a corner of the float bowl. When it gets clogged the engine will only start easily when it is warm.

Verify all jets and fuel or air passageways are open, using wires and or visually with carb spray (wear goggles).

Cable Differences: You can tell what year range a Honda Express is from a distance. A 1977 to 1980 has two cables, a throttle and a choke cable coming straight up from the carburetor.  A 1981 has just a throttle cable coming straight up, but also a vacuum hose for the choke and a float vent hose.  A 1982 to 1983 has a black plastic curved elbow on top, that redirects the throttle cable forward and down, a vacuum hose for the choke, and a vent hose. A 1982-83 also has a different frame, a low headlight, and a two speed transmission.

Comparison of PA MOA-A, PA 08B-B, PA 08B-A, and PA 15A-A

The Honda Express throttle cable curves rearward and loops downward to get below the carburetor, and then goes forward into the frame tube. The loop design adds friction, but it makes a good clean step-thru frame without any cables or wires hanging out.    

Keihin idle mixture screw channels
Left PA08B-B with idle air screw
Right PA15A-A with idle fuel screw

 

 

 

 

You can tell the difference between a carb with an idle air mixture screw, and a carb with an idle fuel mixture screw, by the shape of the casting at the top of the float chamber.

 

 

 


8. Keihin PA 29C-D, PA29H-A, others on #GK8 1984-85 Honda NQ50 Spree
10. Keihin PA 29C-D, PA29H-A, others on #GE8,GN2 1983-85 Honda NM50 Aero 50

Links to Images:
1983 Honda NM50 Aero 50
1985 Honda NQ50 Spree
Spree carburetor PA 29C-D

Keihin (1985-87 Honda NM50) carburetor illustration

The gasket is drawn wrong

These were zippy 50cc two-stroke automatic scooters that maxed out at 30mph to meet many US state’s moped laws. They have electric start so there is 12 volt battery power to operate an automatic electric choke. They also have a gas gauge and an automatic vacuum petcock on the gas tank. You don’t have know very much to operate one. They had a CVT variator that continuously changes the belt drive pulley size ratio, for very quick acceleration. 

PA 29C-D gaskets N/A

The float bowl gasket in the illustration looks like the NC50-type, but it’s not. The actual gasket has an additional loop, for a vent and overflow. A “tall” float bowl gasket for a 1982-83 NC50 would work fine. Only if the float overflowed then some of the overflow would leak onto the carb instead of through the overflow hose and onto the ground.

From measuring an actual PA 29C-D carburetor, the sizes can be displayed in the PA 29C-D gaskets photo. The PA 29C-D gasket set is not available but the PA15A-A gasket set can be a substitute. See above.

Idle Mixture Screw: The idle mixture screw is an “air screw” that blocks off an air channel.

Main Jet: The main jet is a screw-in, recessed-type, M6-0.75 thread, size 68 (0.68mm).

Pilot Jet: The idle jet is not replaceable. It is inside the upper end of the brass tube, pressed into the main body, on the engine side of the main jet.

Float Seat: This carb does not have a replaceable float needle valve seat. The seat is part of the main body, and must be cleaned and polished with a spinning Q-tip.

Float: non-stirrup type white plastic 16013-147-004 see 6-4.0b, non-stirrup needle valve 16155-883-005 see 6-2.0b

Flange Mount: The flange mount holes on the Spree carburetor are spaced 35mm, center-to-center. That is different from the late PC50 32mm, and the NC50 38mm, and Z50 32mm (1976-78 38mm)

Top Cap: M18 x 1 thread

 

 


Mini Cycles

 

9. Keihin Z502 on #045 1968-71 Honda Z50A Mini Trail   

Keihin Z502

Links to Images:
1968-71 Z50A carburetor
1968-71 Z50A carb kit

Flange Mount: 32mm hole spacing, 2 x 18 (22 od) o-ring

Main Jet: This carb has a screw-in main jet #50.

Pilot Jet: It also has a screw-in idle (pilot) jet #38.

Float Seat: It also has a screw-in float needle seat, replaceable.

Float: no-stirrup metal-tip needle valve, metal swinging float

 

 

 

 

 

 

 

 

 

 

 


10. Keihin 655-A on #130 1972-75 Honda Z50A Mini Trail
12. Keihin 674-A on #114 1970-72 Honda QA50
12. Keihin ceto and #129 1973-75 Honda QA50

Links to Images:
1972 Honda Z50A carburetor     1970-73 Z50A drain screw
1974-75 Z50A and QA50 carb kit  This kit is missing the drain plug o-ring and jet pad disk.
1974-75 Z50A and QA50 carb kit  1970-73 carb kit also had a float seat and a float seat washer.

Keihin 655-A, 674-A

 

Flange Mount: 32mm hole spacing, no o-ring groove on carburetor. Instead the o-ring groove is on the intake manifold. Since the 2 x 18 (22 od) intake o-ring is not part of the carburetor, it is not in the Honda gasket set 16010-114-004, or the multi-app set 16010-114-305.

Main Jet: This carb has a “long” press-in jet, with a rubber pad disk under it.

Pilot Jet: The idle jet is not replaceable. It is inside the upper end of the brass tube, pressed into the main body, on the engine side of the main jet.

Float Seat early: The 1970-73 carburetor had a screw-in float needle seat, that was replaceable, like in the illustration.

Float Seat late: The 1974-75 carburetor did not have a replaceable float needle valve seat. The seat was part of the main body, and must be cleaned and polished with a spinning Q-tip.

Float: no-stirrup metal-tip needle valve, swinging float 16013-114-004

Top Cap: M18 x 1.0 thread

Drain screw: 1970-73 chamber set 16015-114-004 had a M4-0.7 thread drain screw with a 2 x 4 (8 od) o-ring. 1974-75 had a M6-0.75 thread drain screw with no o-ring. 1976-78 had a M6-1.0 thread drain screw with a 2 x 2.5 (6.5od) o-ring. 1979-later had a 1.5 x 4 (7od) drain screw o-ring.

 

 

 

 

 


11. Keihin (10 mm) PA 03A-A on #130 1976-78 Honda Z50A Mini Trail
12. Keihin (11 mm) PA 03C-A on #181 1980-81 Honda Z50R
12. Keihin (11 mm) PA 03D-A on #181 1982-85 Honda Z50R
12. Keihin (11 mm) PA 03F-B on #181 1986-87 Honda Z50R  

Links to Images:
1979-81 Honda Z50R carburetor
1982-85 Honda Z50R carburetor PA03D-A
1979-81 Honda Z50R carb kit: D117 thin needle, #58 screw-in jet. Left to right:
drain screw, needle jet (emulsion tube), idle air screw, idle speed screw, float needle

Flange Mount: 38 mm hole spacing 1976-78.  32 mm hole spacing 1979-87.

’76-78 Z50A, ’79-87 Z50R

   quantity
o#
⇓⇓⇓⇓
Keihin PA(a)03A-A  (b)03C-A  (c)03D-A  (d)03F-B
o# abcd price  Honda part#x  description xxx specs
o0 1ooo  N/A 16100-130-641 
o0 1oo0  N/A 16100-130-642 carburetor PA 03A-A Ø10 x 38
’76-78 Z50A
o0 o100  N/A 16100-165-014 carburetor PA 03C-A Ø11 x 32 ’79-81 Z50R
o0 oo10  N/A 16100-181-751 carburetor PA 03D-A Ø11 x 32 ’82-85 Z50R

o0 0001  N/A 16100-181-830
o0 0001  N/A 16100-181-831
o0 0001  N/A 16100-181-832 carburetor PA 03F-B ’86-87 Z50R
o0 0001  N/A 16100-181-850
o0 0001  N/A 16100-181-851
o0 0001  N/A 16100-181-852 carburetor PA 03F-B ’86 Z50R

o1 1o00 $22 16010-081-004 gasket solo-set   1a o d e f o h i
o1 1000 $23 16010-143-305 gasket multi-set 1a c d e f o h i

o1 0100 $18 16010-081-014 gasket solo-set   1a o o o f o h i
o1 0011
$23 16010-165-621 gasket solo-set   o o o o f g h o l
o1 0111 $19 16010-181-305 gasket multi-set 1a o o o f g h i  l

1a 1o00 $$3 00000-000-000 top rubber washer 10 x 18 x 1
1d 1oo0 0$2 16176-551-004 main jet o-ring 1 x 3 (5 od)
1e 1000 $10 16197-063-004 jet support pad disk Ø7.5 x 1.8 
1f 1111 $15 00000-000-000 float bowl gasket  Ø1.5 NC50-type
1g o111 $$2 00000-000-000 drain screw o-ring 1.5 x 4 (7 od)
1h 1111 $$2 00000-000-000 intake o-ring 2 x 18 (22 od)
1i  1000 0$2 16175-260-004 drain screw o-ring 2 x 2.5 (6.5 od)
1l  0111 $$5 16110-181-831 top rubber washer 13 x 19 x 1

02 1000  N/A 16012-130-640 needle set
02 0111  N/A 16012-181-831 needle set
03 1o00  N/A16013-099-691
o3 1o00  N/A 16013-143-620 float set 3a oo 3c 3d black stirrup
o3 o111 $28 16013-147-004 float set oo 3b 3c 3d white regular
3a 1o00  N/A 00000-000-000 float bare, solid black foam stirrup
3b o111 $21 00000-000-000 float bare hollow white plastic regular
3c 1111 $$4 00000-000-000 hinge pin substitute Ø2 x 18.5
3d 1111 $$3 0-93600-04006 hinge screw M4x6 sunk phillips
o4 1100  N/A 
16014-130-640 top set with pipe 4a 1a M18-1.0
o4
0011  N/A 16014-GB1-912 top set with pipe 4a 1l M20-1.0
05 1o00  N/A 16015-130-640 chamber set 5a 1e 1f 5b 1g

05 o110  N/A 16015-099-691 chamber set 5a oo 1f 5b 1g

05 o??1  N/A 16015-130-641
05 o??1  N/A 16015-165-621 chamber set 5a oo 1f 5b 1g

6a 0??1 16016-165-621 
6a ???1 16016-165-505 idle air screw set
6b ???1 16208-GC8-004 idle speed screw set
07 ???? slide set
09
10 1ooo
N/A16011-143-620
10 1ooo $21 16011-881-741 float needle valve  stirrup
10 o111 $24 16155-883-005 float needle valve regular
11 2222 0$1 93892-04012-08 screw & washer M4x12 pan phillips
14 1000 $16 99201-081-0580 main jet push-in #58 0.0228″
14 0100  N/A fixed needle jet and main jet pressed in 0.0228″
14 0011 0$7 99101-187-0580 main jet screw-in #58 0.0228″
18 1111  N/A (not sold separately) idle jet press-in tube 0.015″ pinhole

 

Pilot Jet: The idle jet is not replaceable. It is inside the upper end of the brass tube, pressed into the main body, on the engine side of the main jet.

Float Seat: This carb does not have a replaceable float needle valve seat. The seat is part of the main body, and must be cleaned and polished with a spinning Q-tip.

1976-78 Honda Z50A carb kit
D348 thick needle, #58 press-in jet
 (the jet support pad is not shown)

Carb Kit: Beware of low-cost carburetor kits. In the kit at the right several things are wrong or made badly. 1) it is missing the press-in jet pad disk, 2) the jet o-ring was too big to allow the jet to press in. You can see it seems big in the photo. It was size 1.5 x 4 instead of 1 x 3, 3) the float needle was longer than stock, and the wire stirrup was bent badly in two ways. The throttle (jet) needle was D117 thin instead of D348 thick.

 In 1979 the model name changed from Z50A to Z50R, and the name Mini Trail was dropped.

The 1979-later float bowl no longer has a press-in jet support pad disk 7.5 x 1.8mm.

For some reason in 1979 Honda wanted to make their jets tamper-proof. It’s funny that they went from one extreme to the other, from jets that fall out too easy, to jets that never come out. Both the NC50 and the Z50 changed to “fixed” jets (not replaceable) in late 1978 and 1979. After 1981 the jet was a screw-in, thankfully, like in the illustration

Float: In 1979 the float and float needle changed, from stirrup-type needle valve with black foam float, to no-stirrup needle valve 16155-883-005 with white plastic float 16013-147-004. Like before, the float needle has a rubber cone upper tip and a spring-loaded lower tip. 

 


12. Keihin PA 03H-A on #GW8 1988-88 Honda Z50R
15. Keihin PA 03H-B on #GW8 1988-91 Honda Z50R
15. Keihin PA 03M-A on #GW8 1992-99  Honda Z50R

Links to Images:
1992-99 Honda Z50R carburetor Keihin PA03M-A
1992-99 Honda Z50R carb kit

Flange Mount: 32mm hole spacing

   quantity
o#
⇓⇓⇓ 
Keihin PA (a)03H-A  (b)03H-B  (c)03M-A
o# abc price  Honda part#x  description xxx specs
o0 100  N/A 16100-GW8-671 

o0 100  N/A 16100-GW8-672 carburetor PA 03H-A 1988 Z50R up to JS900485
o0 010  N/A 16100-GW8-673 carburetor PA 03H-B ‘88-91 Z50R mix screw changed
o0 001  N/A 16100-GW8-680 carburetor PA 03M-A 1992-93 Z50R
o0 001  N/A 16100-GW8-681 

o0 001  N/A 16100-GW8-682 carburetor PA 03M-A 1994-99 Z50R
o0 001  N/A 16100-GW8-780
o0 001  N/A 16100-GW8-791
o0 001  N/A 16100-GW8-792 carburetor PA 03N-A
o0 111  N/A 16100-GW8-305 multi-carb  PA 03N-A
o1 111 $23 16010-181-681 gasket solo-set   oo 1f 1g 1h 1l

o1 111 $19 16010-181-305 gasket multi-set 1a 1f 1g 1h 1l
1f  111 $15 00000-000-000 float bowl gasket  Ø1.5 NC50-type
1g 111 $$2 00000-000-000 drain plug o-ring 1.5 x 4 (7 od)
1h 111 $$2 00000-000-000 intake o-ring 2 x 18 (22 od)
1l  111  $$5 16110-181-831 top rubber washer 13 x 19 x 1

05 bowl set
06 screw set
07 slide set
09

 

Main Jet: screw-in #58, M6-0.75

Float: no-stirrup type white plastic 16013-147-004, needle valve 16155-883-005

Top Cap: M20-1.0 thread

In 2000 the Z50R was replaced by the XR50R. The carburetor remained mostly the same.

Idle Mixture Screw: For the entire Z50R year range 1968 to 1999, the idle mixture screw was an air type, not a fuel type. An idle air screw blocks an air tunnel, so tighter is less air (richer). An idle fuel screw blocks off a fuel tunnel. So tighter is less fuel (leaner). 

 


13. Keihin PA 42A-C on #GEL  2000-03 Honda XR50R
16. Keihin PA 42A-A on #GEL  2000-03 Honda XR50R

16. Keihin PA 42A-A on #GEL  2004-09 Honda CRF50F

Links to Images:
2000 Honda XR50R carburetor PA42A-C
2008 Honda CRF50F carburetor  The gasket for this was in use for over 34 years!

This carburetor looks the same as the previous Z50R ones, except the flange is thicker and has square corners, not rounded.

Flange Mount: 32mm hole spacing, thicker with square corners

Chinese re-makes of this carburetor are common on the internet, at incredibly low prices. Read several reviews before buying one. Try to re-use the original Keihin.

In 2004 the XR50R was replaced by the CRF50F. The carburetor remained mostly the same.

Service: Here is a good article about how to remove and clean the non-replaceable idle (pilot) jet.

https://thumpertalk.com/forums/topic/1047667-clogged-pilot-jet-on-a-crf50-success/

The CRF50F idle jet in that article did not crush when gripped lightly with a vise grip pliers. But some pressed-in idle jets have thin walls, or have a tighter fit that needs heavy clamping. Those require a close-fitting drill bit or solid wire, be placed in the hole first, to prevent crushing the tube with the vise grips. It’s a good idea to do that always. 

 

 


Motorcycles

 

14. Keihin PB 15A-A on #GB4  1982-83 Honda C70 Passport (US)

Links to Images:
Keihin PB 15A-A carburetor

Flange Mount: 36? mm hole spacing

   quantity
o#
⇓       
Keihin PB (a)15A-A
o# a price  Honda part#x  description xxx specs
o0 1  N/A 16100-174-673 carburetor PB 15A-A 1980-80 C70
o0 1  N/A 16100-174-772 carburetor PB 15A-A 1981-81 C70

o0 1  N/A 16100-GB5-671 carburetor PB 15A-A 1982-83 C70
o1 1  N/A 16010-GB4-013 gasket solo-set
o1 1  N/A 16010-141-305 gasket multi-set 

 

 

 


Keihin Parts

 

15.  Float needles (valves)

Baby valves: These are the float needle valves for the smallest “baby” Keihin carburetors. Most other float needles are bigger than these, but look the same in photos.

 

16123-063-004 float needle valve $13  all metal type
On road models: 1969-70 Honda PC50, 1969-70 Honda PS50, 1970-72 Honda PC50K1, 1971-73 PF50 Amigo standard (FR DK NE), 1971-73 PF50 Amigo Graduate (UK), 1970-71 PS50K1, PS50K1 (NE), others

 

16011-881-741 float needle valve $21 stirrup type
supersedes 16011-143-620  16011-147-004

On road models: 1977-79 Honda NC50 Express (with PA08B-A carb), 1978-79 PA50I and PA50II Hobbit, 1976-78 Z50A Mini Trail  Off road:
1976-78 Honda Z50A, 1977-79 XL75, 2004-07 CR80F, 1976-78 XR75, 1979-84 XR80, 1985-03 XR80R, 1977 CT125, 1976 TL125

 

16155-883-005 float needle valve $24 regular type
On road models: 1973-77 Honda PC50K1, 1973-78 Honda PF50 Amigo/Novio, 1978-83 Indian AMI-50, 1979-83 Honda NC50 Express (with PA08B-B carb), 1980-83 PA50II Hobbit, 1979-81 NA50 Express II, 1981-82 NX50 Express SR, 1982-83 NU50 Urban Express, 1980-83 C70 Passport, 1978-79 CT90 Trail 90, 1986 CT110 Trail 110, 1982 MB5, 1990 NS50, 1984-85 NQ50 Spree, 1988-90 SA50 Elite 50, 1985-91 CH80 Elite 80 
Off road: 1979-99 Honda Z50R, 1988 ZB50, 2000-03 XR50R, 2004-12+ CRF50F, 2004-09, CRF70F, 1978-82 CT70, 1997-03 XR70R, 1978-79 Honda CT90, 1980-84 CT110

 

Valve seats: The seat is the hole that the needle tip seals against. These “baby” Keihin PA series carbs have non-replaceable valve seats. Most motorcycle carburetors have replaceable float valve seats that screw in or push in. The seat is normally replaced with the needle. With these the seat must be cleaned, polished and inspected. It’s a tiny round hole at the end of a dark small round tunnel. It’s hard to see. It must be perfectly circular with no nicks or scratches on the edge of the hole, where it seals against the rubber cone tip of the needle.  The walls of the tunnel must be clean, smooth and shiny or the float might stick open a little and cause an overflow leak.

Beware of low cost float needles (valves). These have to be made precisely the same as originals in order to function properly. In the photo, the left one is a 16011-991-741 generic low-cost replica, made incorrectly. The stirrup wire is bent and the needle is longer. The right and middle are 16011-991-741 Honda originals (or KL-made replicas) for comparison, made correctly. 

 

 


Chamber families 165, 147A, 191, GK8

16.  “baby” Keihin float bowls

Here the chamber sets from above are all listed together, along with the carbs and bikes they go on. A chamber set includes the float bowl, float gasket, drain screw, and drain screw o-ring. As a courtesy, here are the links to CMS in Netherlands where you can view their image and see their price and availability.

Families: A chamber set family is one or more chamber sets that can interchange.

Jet pad: Before about 1980 these carburetors had push-in main jets. The push-in main jet was supported by a pill size rubber pad. The jet pad was held by a circular wall in the bottom of the float bowl. You can see that in the image on the right. The second bowl is for a jet pad, but the first bowl is not.

Choke jet: Carbs with fuel enrichment  type chokes have a jet in one corner of the float bowl (2nd, 3rd, and 4th in the image). Carbs with air valve choke plates do not have a choke jet (first in the image).

  Float Bowls (chambers) with no choke jet  =================    chamber     gasket


16015-064-004                                064 family
cmsnl.com roundish shape, shallow for jet pad, no choke jet
on carbs C4A C5A C5B F4A F5A lever-plate choke
on bikes 69-70 PC50/PS50, 70-73 PC50K1/PS50K1, 71-73 PF50


16015-114-004                                114 family
cmsnl.com roundish shape, deep for jet pad, no choke jet
on carbs 655A 674A lever-plate choke
on bikes 72-75 Z50, 70-75 QA50


16015-081-004                                081 family
cmsnl.com NC50-shape, shallow for jet pad, no choke jet
on carbs PA00A PA01A lever-plate choke
on bikes 73-77 PF50R, 73-78 PC50K1

16015-130-640  
 cmsnl.com NC50-shape, shallow, for jet pad, no choke jet
on carbs PA03AA lever-plate choke
on bikes 76-78 Z50A, 79-81 Z50R and other Z50’s


16015-099-691                                165 family
cmsnl.com NC50-shape, shallow, for no jet pad, no choke jet
on carbs PAM0A PA03HA PA03HB PA03MA others lever-plate choke
on bikes 78-83 Indian, 88-99 Z50R, 04-05 CRF50F many others

16015-130-641 16015-165-621
 cmsnl.com NC50-shape, shallow, for no jet pad, no choke jet
on carbs PA03CA PA03DA lever-plate choke
on bikes 80-85 Z50R

same

16015-165-920 16015-165-621
 cmsnl.com NC50-shape, shallow, no jet pad, no choke jet
on carbs
on bikes

16015-165-621 16015-165-B10
 cmsnl.com NC50-shape, shallow, for no jet pad, no choke jet
on carbs PA03FB lever-plate choke
on bikes 86-87 Z50R

same

16015-165-B10
 cmsnl.com
 NC50-shape, shallow, for no jet pad, no choke jet
on carbs PA03?? lever-plate choke
on bikes 93-96 Z50J (Japan model)

 

  Float Bowls (chambers) with choke jet  =================    chamber     gasket


16015-147-004                                147A family
  cmsnl.com NC50-shape, shallow, for jet pad, with choke jet
on carbs PA08BA  black float, cable-enrich choke
on bikes 77-78 NC50


16015-147-014                                 147B family
 cmsnl.com  NC50-shape, shallow, for no jet pad, with choke jet
on carbs
PA08BB 08EA 08EB 08DA white float cable-enrich choke
on bikes 78-80 NC50, 79-80 NA50


same

16015-187-043 use 16015-191-034  191 family
 cmsnl.com NC50-shape, deep, for no jet pad, with choke jet
on carbs PA13EA                 white float vacuum-enrich choke

on bikes 82-83 NU50, NU50M

16015-187-671 use 16015-191-034
 cmsnl.com NC50-shape, deep, for no jet pad, with choke jet
on carbs PA13BA                 white float vacuum-enrich choke

on bikes 81-82 NX50

16015-191-014 16015-191-024
 cmsnl.com NC50-shape, deep, for no jet pad, with choke jet
on carbs PA15AA PA16AA  white float vacuum-enrich choke

on bikes 81 NC50, 81 NA50

same

16015-191-024 ⇒ 16015-191-034
 cmsnl.com NC50-shape, deep, for no jet pad, with choke jet
on carbs PA15AA PA16AA  white float vacuum-enrich choke

on bikes 81 NC50, 81 NA50

16015-191-034   available soon
 
 cmsnl.com NC50-shape, deep, for no jet pad, with choke jet
on carbs
PA15AA PA16AA  white float vacuum-enrich choke
on bikes 81 NC50, 81 NA50

16015-GA6-671 use 16015-191-034
treatland.tv NC50-shape, deep, for no jet pad, with choke jet
on carbs
PA13EA                 white float vacuum-enrich choke
on bikes 82-83 NC50


16015-GK8-671                                GK8 family
  cmsnl.com  NC50 with outer loop, very deep, choke jet
on carbs
PA29CD PA29HA others electric-enrich choke
on bikes 84-86 NQ50, 83-85 NM50

 

 


17.  Gasket Multi-App Sets (for several carburetors)

There are 100’s of vintage Honda carburetors. Many share the same gaskets, but have maybe one or two things different. To reduce the number of different gasket sets, Honda combines several sets into one multi-set. In a multi set there are extra “optional” gaskets, that may or may not be needed. These are in separate packages labeled A or B. There is a sheet of paper with a table of replacement gasket set part numbers, the specific part numbers they replace, and a number, usually 1 or 0, in the A and B columns, telling how many of each “optional” gaskets are required.  

 

16010-114-305

16010-114-305 $18
fits 1972-75 Honda Z50A Mini Trail
fits 1970-75 Honda QA50
1p top rubber washer 10 x 15 x 1  
1q (A) drain screw washer 3 x 6 x 0.5
1d main jet o-ring 1 x 3 (5 od)
1e jet support disk Ø7.5 x 1.8? 
1n float bowl gasket 1.5 x 40 (43 od) 
1r drain plug o-ring 2 x 4 (8 od)

 


16010-143-305

16010-143-305 $23    
fits 1976-78 Honda Z50A Mini Trail, 1979-81 Z50R
fits 1977 NC50 Express and some 1978 (except for the drain plug o-ring)
fits 1970-77 PC50K1 and 1978-80 Indian AMI50 (except drain plug o-ring)

1a top rubber washer 10 x 18 x 1
1h (A) intake o-ring 2 x 18 (22 od) 

1c (B) intake o-ring 2 x 20 (24 od) 
1d main jet o-ring 1 x 3 (5 od)
1e jet support disk Ø7.5 x 1.8 
1f  float bowl gasket Ø1.5 NC50 type
1i  drain plug o-ring 2 x 2.5 (6.5 od)

 


16010-147-505

16010-147-505 $21 
fits 1979 NC50 and some 1978 (except for the intake o-ring)
fits 1979-80 NA50 and NC50 (except for the intake o-ring)
fits 

1b top rubber washer 13 x 16.5 x 1
1h intake o-ring 2 x 18 (22 od)
1d (A) idle fuel screw o-ring 1 x 3 (5 od)
1g (A) drain plug o-ring  1.5 x 4 (7 od)
1f  float bowl gasket Ø1.5 NC50 type
1i  (B) drain plug o-ring 2 x 2.5 (6.5 od)

 


16010-156-305

16010-156-305 $15   
fits 1978-83 Honda PA50
1c intake o-ring 2 x 20 (24 od)
1h intake o-ring 2 x 18 (22 od)
1g drain plug o-ring  1.5 x 4 (7 od)
1j float bowl gasket 2 x 50 (54 od)

 

 


16010-181-305

16010-181-305 $19  
fits 1979-86 Z50R, 2000-03 XR50R, 2004-11+ CRF50F
1a top rubber washer 10 x 18 x 1
1h intake o-ring 2 x 18 (22 od)
1l  top rubber washer 13 x 19 x 1 
1g drain plug o-ring  1.5 x 4 (7 od)
1f float bowl gasket Ø1.5 NC50 type

 

 


16010-GF8-305

16010-GF8-305 $25  
fits 1981-82 NX50, 1982-83 NC50/NU50

1b top rubber washer 13 x 16.5 x 1
1c intake o-ring 2 x 20 (24 od)
1d (A) idle fuel screw o-ring 1 x 3 (5 od)
1t (B) o-ring 1.5 x 8.5 (11.5 od)
1u (B) nylon washer 6.2 x 11 x 0.8
1g drain plug o-ring  1.5 x 4 (7 od)
1k float bowl gasket 2.5 tall x 1.5 wide NQ50 type

 

 


18. Jets

99201-081-0700

  ∅ 5   P U S H – I N    J E T S   ∅5.0 x 9.5 with o-ring 1 x 3 (5 od)
 ===========================================
 N/A 99201.081.0500 jet push-in 50 
 N/A 99201.081.0520 jet push-in 52
 N/A 99201.081.0550 jet push-in 55 C4A C4B F4A C5A

$16 99201.081.0580 jet push-in 58 PA 03A-A
 N/A 99201.081.0600 jet push-in 60
 N/A 99201.081.0620 jet push-in 62 C5B F5A

$16 
99201.081.0650 jet push-in 65 PA 01A
 N/A 99201.081.0680 jet push-in 68 

$16 99201.081.0700 jet push-in 70 PA 00A
 N/A 99201.081.0780 jet push-in 78 PA 08B-A
$23 substitute jet, #70 drilled to 78 PA 08B-A

 

99101-187-0700

M 6   S C R E W – I N   J E T S    M6-0.75 thread 
===========================================

0$7 99101-187-0580 jet #58 PA03DA PA03FB 82-87 Z50R
 N/A 99101-187-0600 jet #60
 N/A 99101-187-0640 jet #64

0$7 99101-187-0680 jet #68 PA29CD PA29HA 84-87 NQ50
$$7 99101-187-0700 jet #70 PAMOA PA25A ? 78-80 Indian, 82-83 NC50I
0$7 99101-187-0750 jet #75 PA15A 16A 13BB 81-83 NC50, 81 NA50
0$7 99101-187-0760 jet #76
0$7 99101-187-0780 jet #78 PA13BA 81-82 NX50
0$7 99101-187-0800 jet #80
 N/A
99101-187-0820 jet #82 
0$7 99101-187-0850 jet #85 PA13EA 82-83 NU50

 

99101-124-0700

M 7   S C R E W – I N   J E T S    M7-0.75 thread 
===========================================
 N/A 99101-124-0600 main jet 60 21A
 N/A 99101-124-0780 main jet 78 20A

 

 

 

 

 

 


19. Where else to get Keihin parts

Consolidated Motor Spares B.V. (CMS): This is an excellent online store from the bike-loving nation of Netherlands that has “every” Honda part. They have parts schematic illustrations for every Honda model worldwide, and photos of every part on every Honda, and not just motorcycles. And not just Honda, but also Kawasaki, Suzuki, and Yamaha. Much of the information of the Honda “Baby” Keihin carburetors came from CMS. https://www.cmsnl.com/