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TOPIC: Replaced the Chinese carb with rebuilt Mikuni VM24SH

Replaced the Chinese carb with rebuilt Mikuni VM24SH 15 Apr 2019 17:13 #1

  • DD430
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Good evening folks. I took the CT2 out on a maiden voyage a few weeks ago and the bike ran OK at higher RPM's but it stumbled a bit getting there. On the way home it really went south on me. When I pulled it apart I found that the pilot jet had dropped into the float bowl. Pretty indicative of Chinese manufacturing - I'm sure that they'll improve things but they're not there yet.

The bike came with the original carburetor that really was in pretty good shape considering it's age - no ethanol eaten parts - so I ordered a rebuild kit from Keyster along with new jets using the same numbered jets that the carburetor housed (I think) originally. I took the carb apart and dunked it in Berryman's carb cleaner for a 1/2 hour in order to clean out any 'hidden' residue and rebuilt it today - new jets, choke assembly, gaskets, & etc. It's now back on the bike and I'm ready to give it a 'kick'.

The question is this: Anyone have an opinion as to where to set the both the air screw and throttle/idle screw? Since the Chinese carb was 'suspect' to begin with I don't want to set those two parts on the Mikuni using the Chinese carb as a 'template' in terms of 'how many revolutions' in and/or out I set them. I did set the 'c' clip needle two slots down from the top - just where I found the original to be set.

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Sears Allstate 106
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Last Edit: by DD430.

Replaced the Chinese carb with rebuilt Mikuni VM24SH 15 Apr 2019 17:24 #2

  • MarkT
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If you use the Keyster jets, it probably won't be much better than the Chinese carb? I recommend staying with the original Mikuni jets and slide needle.

Air screw setting is usually about 1.5 turns out from lightly seated. Manual will have the exact factory spec.

On the stop screw, best to err on "too far out". It's easy to keep it running with the throttle grip and turn in the screw to get it to stay at correct rpm.
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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

Replaced the Chinese carb with rebuilt Mikuni VM24SH 16 Apr 2019 06:08 #3

  • DD430
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Thanks, Mark. I'll give it a try. By the way, I did ned up using genuine Mikuni jets from Niche Cycle but used gaskets from Keyster.

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Sears Allstate 106
Honda Superhawk CB77E
BSA Starrfire
BSA Goldstar
Honda 400T
BMW K75
BMW R1100
BMW R1100RT
Honda Elite 80
Yamaha CT 2

Replaced the Chinese carb with rebuilt Mikuni VM24SH 16 Apr 2019 06:41 #4

  • MarkT
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DD430 wrote: Thanks, Mark. I'll give it a try. By the way, I did ned up using genuine Mikuni jets from Niche Cycle but used gaskets from Keyster.


Perfect! I wasn't sure and had to say something because of the grief the Keyster jets often cause. :likey

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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