Engine only 2-strokes under the right load

Discussion in '2-Stroke Engines' started by Just_Gasit, Jul 12, 2009.

  1. Just_Gasit

    Just_Gasit Member

    I'm still in break in period and find I only hear proper combustion under just the right load, the rest of the time it 4 strokes or semi spudders. I'm hoping the 25:1 mix is the main cause as I plan to run 32:1 after I burn 2 gallons. I played with the needle and that wasn't it. I have no air leaks, filter is fine. Adding choke bogs it down. I don't have an idle mixture screw on the carb that came with my kit, doesn't have a place for one either. Too bad, it's useful for low end and off idle mixture. Do these HT motors just run like this normally? Can't be good for plug life or fuel economy.
     

  2. ratty

    ratty New Member

    I'm pretty sure its just the nature of the beast. All mine run that way. Only having one gear doesn't help either!
     
  3. Hawaii_Ed

    Hawaii_Ed Member

    The kits do not have an idle mixture screw, that is just a bump stop for the slider. The carbs have an adjustable clip for idle and off idle mixture. All the way up is lean, all the way down is rich. However it does not impact WOT. As stated above, lots of these engines seem to sorta run that way, but you can tweak it some with the clip.
     
  4. nadroj

    nadroj Member

    break it in first then it will run better
     
  5. Just_Gasit

    Just_Gasit Member

    Update

    Starting into my second gallon of fuel and it is starting to run better. I remember breaking in a KX 250 years ago and it never ran all that poorly. I guess these little China dolls have a different temperment. Bugs are working out, things are getting tweeked, a quality drive chain is on order and I've ridden it to work since last Friday. Another week and I'm sure there will be further improvement.
     
  6. radrob

    radrob Member

    200 to 300 miles is where mine smoothed out
     
  7. Nitropeewee

    Nitropeewee Member

    mines got 600 plus miles on it runs great! it acts the same way. its not 2 strokin till it gets under load n gettin some gas(up hill er realy on the throttle) i run about 32-1 with a lil lucas gas treatment does great only runs about 175 to 205 degrees @ 22-24 mph all day long.
     
  8. arceeguy

    arceeguy Active Member

    All two strokes will "four stroke" under light load. So when you are just cruising, the engine will oscillate between two stroking, and four stroking. Once under load, the four stroking should stop. If it doesn't stop, you can try lowering the jet needle by raising the C-clip a notch or two.

    My old two stroke lawn boy mower soumds like h3ll under light load, but once it hits thick grass and the governor applies more throttle - I get the nice strong buzzing as the mower powers through. Same goes for my HT engine. It doesn't really sound all that smooth when I'm loafing along at 20mph, but it sounds great when accelerating or flying down the road WFO.
     
  9. Just_Gasit

    Just_Gasit Member

    Update

    I live at 4500 ft and finally went ahead and soldered up the main jet and redrilled with a #74 bit. this was about 2 sizes smaller than original. The WOT is perfect, 2 strokes mostly, fades to a 4 stroke as the load is lighter. I moved the clip all the way up and this greatly improved the midrange too. Needle had almost no effect before since the main was just way too rich. (plug was black BTW) I also added the very small hole from the bowl to the forward center edge of the slide to act as an idle circuit, another improvement. I also did a exhaust mod, I removed the end cap, cut the outter large tube and then modified the core hole arrangment. I removed the baffle plates, and drilled more holes further up the core tube, I welded up the holes that are near the bottom end but left the small gap at the end plug where the cap bolts on to prevent gunk from pileing up inside. I then rewelded the outter tube back in place. I cut the small tube flush with the inside of the cap and using the left over piece, I drilled a second "small" pipe hole next to the original, welded in and cut flush too. I then inserted a copper pot scrubber mesh and capped it at the end with 1/8 metal hardware wire to prevent the scrubber stuff frome being blown out over time. I then put the cap back on. It's quieter than original and keeps the catalyst piece functional and flows better.
     
  10. arceeguy

    arceeguy Active Member

    I'm within a couple hundred feet of sea level, and I have had to drop the needle because of rich low/mid speed and drill the jet one size up to eliminate lean bog near WFO. In colder weather (below about 55), the main jet needs to be hogged out two sizes larger.

    At 4500 ft. these things must be spitting fuel out of the box!
     
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