Engine Trouble jerking and bucking at low speed. 10 - 15 mph

Discussion in '2-Stroke Engines' started by VenturiEffect, Apr 13, 2015.

  1. VenturiEffect

    VenturiEffect New Member

    So ive recently got into performance mods. Mainly for speed. And torque balance. 32 tooth, sbp x chamber and a dellorto sha clone carb. I installed all of these at the same time. #65 jet in the carb extended intake manifold and 13 inch header on the pipe. From flange to very beginning of expansion bell. It starts right up. With ease I mean one turn of the pedals and bam. But when I get up to maybe 10 mph hit the gas and it like a bucking horse jerking and misfiring. Not a steady idle. Not sure what going on here. Im thing about putting the stock exhaust back on and try to tune the carb a little richer then put.the x chamber back on. Any thoights on what may be causing this? 20150411_125826.jpg
     

  2. VenturiEffect

    VenturiEffect New Member

    Also the engine is a gen IV dax build f80
     
  3. jaguar

    jaguar Well-Known Member

  4. VenturiEffect

    VenturiEffect New Member

    Its all flat land here not to mention im at sea level. And completely clueless when it comes to jetting and diagnosing
     
  5. VenturiEffect

    VenturiEffect New Member

    Ive also noticed since ive put the carb on that it seems to flood alot. It literally sucks the gad out alot better or it could be that I swapped frames and the tank is tilted downwards in the back
     
  6. jaguar

    jaguar Well-Known Member

    click on my signature link and read the section on jetting
     
  7. VenturiEffect

    VenturiEffect New Member

    Would you happen to know what jet size I would need for sea level I checked your chart out but not understanding it to well
     
  8. Timbone

    Timbone Active Member

    You are turning a 32 tooth cog. My math for a 26" wheel:

    2500 (RPM) / 4 (internal reduction) /2.9 (11x32) x 81.64 (26" wheel circumference) /12 (feet) /5280 (ft) x 60 (mph) = 17mph

    My 41 cog figures out to 13mph @ 2500 rpm. That's a big difference! Of course, you can get 40mph @ 6000 rpm! Zoom!

    This has to be a factor, especially if the engine isn't performing perfectly.

    =Timbone=
     
  9. VenturiEffect

    VenturiEffect New Member

    Could that be the problem timbone. Im thinking that might be it.
     
  10. jaguar

    jaguar Well-Known Member

    there are too many factors that affect what size jet is needed.
    you just have to buy some smaller ones and try them out.
    I prefer to just use micro drill bits and fill the jet hole with solder and then drill a new hole. that saves the cost of having to buy 6 different jets.
     
  11. VenturiEffect

    VenturiEffect New Member

    Yeah I might end up doing that. I already have micro bit around. What solder should I usr
     
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