Hello I have a coolster 110cc that will drive by itself at idle. It is still drivable but you have to hold the rear brake while at stop . I have had this ATV new since 2017 and have not done any modifications... I have played around with the idle screw with no success thank you.

 

Have you slowed the idle down to stalling point? If it still "runs away" at this engine speed, you have a problem with the clutch. No idea what type a Coolster has. Most circa 110cc bikes have a lawnmower style centrifugal, but some of those using variable belt drive just let the belt get slack enough to slip at low revs.

 

Thanks for the reply ,It’s a 3050C...the problem is still present but way better at low idle...thing is where we ride is high altitude so I usually have to crank up the idle really high to keep the atv from not stalling..and that’s when it really wants to take off ...

 

I don't normally recommend touching the idle jet, but your circumstances dictate that the standard setting may be rich, lean it down a little, and you may find you can sustain a lower idle speed setting.