Coolster 125 Pitbike bogging issues - Page 3

Dusman · 08-22-2019, 09:41 PM

Hi fellow ChinaRiders,

I have a 2016 Coolster 125 pit bike that had a hard time starting, continuing to idle once hot, and regardless of whether it was cold or hot, it would begin to bog down when you reached 3/4 throttle. Instead of trying to crack the tamper proof stock carb, I simply purchased a PZ22 mikuni clone on Amazon and installed it today. Carb got installed, idles like a champ now, starts no problem, but the bogging is still there at 3/4 throttle and its slightly worse now. I fiddled around with the mixture screw and it didn’t seem to really make much difference so I left it at about 2 turns out.

I did also try to check the valve lash, but if you are familiar with these bikes, you can’t get a standard feeler gauge in there since the valve tappets are somewhat sunk down into the top of the head inside of a @ 1.5 inch valve cover hole.

It seems to me at this point it either has to be (1) valves or (2) jets.

What kind of feeler gauge do you use to check your valve lash on these bikes and what size pilot and main jets do you use?

I’m approximately 980 ft above sea level.

08-22-2019, 09:41 PM	#1
Dusman Join Date: Jan 2018 Location: NC Posts: 214	Coolster 125 Pitbike bogging issues Hi fellow ChinaRiders, I have a 2016 Coolster 125 pit bike that had a hard time starting, continuing to idle once hot, and regardless of whether it was cold or hot, it would begin to bog down when you reached 3/4 throttle. Instead of trying to crack the tamper proof stock carb, I simply purchased a PZ22 mikuni clone on Amazon and installed it today. Carb got installed, idles like a champ now, starts no problem, but the bogging is still there at 3/4 throttle and its slightly worse now. I fiddled around with the mixture screw and it didn’t seem to really make much difference so I left it at about 2 turns out. I did also try to check the valve lash, but if you are familiar with these bikes, you can’t get a standard feeler gauge in there since the valve tappets are somewhat sunk down into the top of the head inside of a @ 1.5 inch valve cover hole. It seems to me at this point it either has to be (1) valves or (2) jets. What kind of feeler gauge do you use to check your valve lash on these bikes and what size pilot and main jets do you use? I’m approximately 980 ft above sea level.
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