HS 142 pulls hard to mid power then bogs and stutters

Discussion in '4 Stroke Bicycle Engines & Kits' started by Timcocycle, Oct 24, 2016.

  1. Timcocycle

    Timcocycle New Member

    Oct 24, 2016
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    Hello all. I just built my HS four stroke and took it out for the maiden voyage.
    The only mod I did was take off the black box muffler and put the generic chrome
    2 stroke pipe on. The bike idles just fine and accelerates hard up until 3/4 throttle then
    Starts losing power and stuttering. I can hold the the throttle maxed and it will go a constant 23 but no more. Gas flows like a river to the carb so no flow issue there. Anybody have an idea of what is going on? It'll idle all day even after bogging around for ten miles. Stock plug as well. 89 octane gas. Valves set at .01 maybe a little less. Any help would be Much appreciated. :-||
  2. Agreen

    Agreen Member

    Feb 10, 2013
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    Sounds like the carb is too lean on the main jet.
  3. KCvale

    KCvale Well-Known Member

    Feb 28, 2010
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    Sounds like valves to me but one easy thing you want to do anyway is a NGK 7544 (CR7HIX) Iridium spark plug, no matter what else may be an issue, that's the plug you want for the best performance on the HS engines.

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