so we have a 97 or 98 kx125 motor on a shifter kart... and it runs like crap and i need help.

so heres what its doing, lugs pritty bad on the bottom but doesnt smoke like its fat, and up in the high RPMs it feels like its got a speed limiter.

here has what i have done so far, changed reeds, rebuilt carb, changed carb, changed jets, trimmed the plug wire back, pinched the plug wire cap a bit, changed plugs, changed fuel pump, made sure the coil had a good ground and changed the fuel filters.

so im stumped, could the timing be off? is the timing adjustable on these things. im used to chevy v8's in sprint cars, lol these things are a differant world