150cc GY6 "jerk" on throttle

[catchacuda]

Hey, here we go again with an atv.
It's an AlphaSports LG 150 gy6. After going through some wiring we got spark. The carb was full of crap, looked like saw dust, cleaned it spotless and got it running.

While accelerating, maybe 1/2 throttle and up, you experience a pronounced "jerk" sensation, let off the throttle and you're fine. If you stay in the throttle, it will jerk once, smooth out and repeat. Other than that It behaves pretty well. Im not sure weather to start looking at a fueling issue or maybe cvt related?

Any input?

Just realized I posted in the wrong area doh!

[edwardtennant]

what colour is the spark plug? could be rich or lean

[90GTVert]

I moved your post. No worries.


Something that may help here and with many other issues in the future :

-If the issue is throttle dependent (only happens at 1/4 throttle or 1/2 throttle to WOT or wherever), then it is usually best to start with the carburetor and related issues for your troubleshooting.

-If the issue is speed dependent (only happens at launch, at 20MPH, at 50MPH, etc...), then it is most often better to start your search with the CVT.



Problems only 1/2 throttle and up and often related to the main jet size.

Some symptoms of rich and lean tunes that may help :
www.49ccscoot.com/faq/symptoms.html

A quick and simple trick if you are unsure if it's rich or lean is to put a little electrical tape across a small portion of the airbox inlet. Don't over more than half of it, preferably no more than a 1/4 of it to start. That will richen it up (as long as the airbox is sealed to the carb) and you can see if the condition improves or degrades. This isn't a replacement for having main jets on hand for tuning, but it can help for faster diagnosis.