MikeJ-2009

98 Yamaha PW80

Carb rebuilt 1 year ago. Ran great for a long time. Occassionaly started dying during 50%+ throttle. Filed plug and ran fine again. Started doing it more and more, and finally wouldn't take any throttle.

Plug splattered with oil. Disabled stock auto-lube pump. Running pre-mix now.
Took top end apart, put back together, new plug, pre-mix.

Started fine today, adjusted carb to factory specs, idles fine. Light throttle runs fine, 40%+ throttle it bogs like it's dead. 40%+ throttle with choke open runs perfect, but during 40% and under with choke open it dies.
Idle and part throttle with fine air/fuel, full throttle with no choke and it's super lean and dying.

Who knows how to diagnose the part of the carb I should be looking at? The only other change I made is running toulene up to 100 octane. I'm stumped.

#1NISMO

idk is it still stock bore, when u had it apart did u put new rings and a piston in it ? maybe running premix it needs a lil bigger main jet if it mixes the oil and gas normally after that piont, otherwise idk

MikeJ-2009

I've really kinda narrowed it down to the carb, but I don't know ---- about carbs, so I don't know what potentially would be the first thing to look for. Fiddling with the choke while riding makes it run like woah, so it's got something to do with the fuel. Maybe I'll tear the carb out and just clean everything.

WTF

on my 50 it did that untiill i messed with the screws on the carb. i dont know what i did but i think its like one is for over half throttle adjustment the other is for idle and the other is somthing else. somthin like tha.t

mine was a honda 50 though with a 82cc big bore. and oversized carb. that thing ripped. i sold it cause i always limping away from this tiny bike bloody. good times.

bigdaddyvtec

needle valve/slide is all good

SOunds like the carb needs a serious douching with some carb cleaner..... Sounds like its starving for fuel.....

WTF

i think i raised or lowerd it a notch i dont remember. fuc carbs

b18.

Its bogging down like there is too much fuel or is it starving, like cutting out when you apply throttle? Regardless take it off and give it a good carb cleaner bath, make sure that the reservoir is getting fuel and the induction line isn't clogged, (little straw dipping into the fuel bowl). It seems to me that the thing is starving when you gas it, probably because the needle is all gummed up, single jet 2-stroke carbs always do that ---- because of the added oil. Be glad its not a floating ITB carb set up 4cyl motor, that is the biggest pain in the *** calibrate ever.

sikcrx89

you know i pulled out my pocket bike yesterday and it was doing the same thing chcoking out at 50%+ i pulled the the carb bowl drain screw and it was barely dripping gas from the bowl.. i found out it was the fuel on/off valve the little rubber washer or whatever was fuckign the flow up and the bike was running out of gas up top.. i pulled the one screw out of the valve and just broke the other one loose and gas sarted rolling out of the bowl and that what fixed mine.. not sure if your has like a ball valve/fuel valve to turn the gas on/off but if it does break it loose and make sure the carb is getting good fuel flow