Hi,

I've got 2 Coolster 125cc model ATV3125B for my kids.

Got them working (after replacing coil, ignition switch, battery, spark plugs, etc.).

Tuned the air-fuel mixture with just the screw (uses PZ25 -- anyone know if lean is turning screw out or in?????).

Both quads will ride for 45-60 minutes and then stall and get very hard to start.

If I let them cool a while, they're fine again.

Anyone have any suggestions?

Thanks,

Joseph

 

I'm no expert when it comes to these china built quads , but turning the fuel misture screw in leans and turning it out enrichens it ; sound's like you've had a run of bad luck with this quad !

I hope it was new and the parts you had to replace were provided free of charge by the company you bought it from , i've read here on the forums that some of the companies/Dealers gave them these parts free ; while some others wouldn't i hope you were one of the lucky ones and good luck with the quad !......

 

The dealer has been helpful and has supplied the parts at no charge (but with wrong parts and delays).

I can't figure the screw out. On another site, it says that the mixture screw is an air bleed adjustment, so screwing it IN is enrichening it.

UGH!

 

try a valve adjustment, could be tight valves.

 

I've never done a valve adjustment and don't feel too confident about it. Do valve tolerances change over the first 45 minutes of running?

 

if the factory didn't correctly set the valve clearance to begin with and were set up tight as soon just as the engine was fired up the valves will only get tighter because heat causes the metal to expand, what happens, if they were set up to tight the valves now with the heat will not close al the way causing the engine to quit running until cooled off and the metal shinks again. valve adjustment on these engines take appox 30 minutes or less. if you need instructions on how to adjust the valves you can e-mail me at luvmysxs@yahoo.com .

one more thing i would also take a look at would be the fuel tank vent, usally in the fuel cap , if your fuel cap doesn't have a vent then its like the hibirds 110's that vent thru the carburetor) if it's plugged then it will also stop fuel flow. this also would make your quad quit running, this is easy to check out, just loosen the fuel cap or remove it and run the quad and see if it still quits.