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Thread: atc90 stroker carby help

  1. #1
    vroomy's Avatar
    vroomy is offline At The Back Of The Pack Arm chair racerFirst time rider
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    atc90 stroker carby help

    hi, finally got my atc90 motor back from a fresh build. Its running a Helm&Son stroker crank with 54mm piston which should be around 133cc? anyhow im trying to figure out what size carb i should run? i have a 26mm mukuni and a 21mm keihin copy any of those work well? i was going to run the 26mm but it wont fit my sudco manifold, the bolt holes on the mikuni are slightly offset. Can anyone here give me some advice? cheers

  2. #2
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    26mm is a little to big IMO , it will work but throttle response will be boggy , 21mm might be fine but I’m not a fan of China carburetors .
    A genuine VM22mm or VM24mm mikuni round slide is you best bet or a old school 24mm Keihin if you can find one .
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  3. #3
    vroomy's Avatar
    vroomy is offline At The Back Of The Pack Arm chair racerFirst time rider
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    Ok ill start looking. Any idea what manifold fits these larger carbs properly?

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    Quote Originally Posted by vroomy View Post
    Ok ill start looking. Any idea what manifold fits these larger carbs properly?
    I believe the bolt width on a 26 is a bit wider than a 22 but I could be wrong. I've never had an issue with my 22's on any of the four aftermarket intakes I have.
    And make sure you are getting a genuine mikuni, there are plenty of copies ones on the market.
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  5. #5
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    I agree with Mike. A 26mm is almost too big for even a 180 motor. The VM22 would make your 90 scream. Will be a lot more responsive than anything larger.
    At 133cc and 54mm Bore you should have a 58mm Stroke. Good running little set up.
    * 1978 ATC 90/180 Pauter PJ1 / Springer "Team BAPP" Bike *

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