Apr 14, 2013
Hey guys new to forum. But not new to motors and wrenchin on stuff.

I got a CR125 that seems to idle high at time and then fades out and wants to die. Yes I have played with the idle screw on the choke knob. I feel if I turn the idle up any higher it is going to rev way to high while idling.

My air flow screw is turned out 1 and half turns.
Ive rebuilt the top end couple weekends ago. I cleaned air filter and oiled it. Cleaned carb. What else could be causing this problem? Only thing I can think of is something with the jetting or something...? I don't know much about jets and needles.

It was like this last summer but just dealt with it by continuing to rev it well riding so it didn't die while stopped.

Prob gonna go riding next weekend so want it to run better. Gonna rip it up in 2 weekends for sure so needs to be running great then.


Mar 13, 2013
Check Air Boot, and Intake boot, for leaks. I would even go as far as pulling the PV cover off and checking the bearing seal that the PV rod goes through. Mine had like a 2-3mm gap inbetween the rod and seal that I replaced and fixed my high idle problem. I also pulled the float bowl off and pulled SJ and MJ and prayed with carb and choke cleaner.

I also read that if your silencer isnt packed you will never get a good jetting to stick. So If your silencer is due I would re-pack it.

Rich Rohrich

Moderator / BioHazard
Jul 27, 1999
.. and also keep in mind it's a 125 two-stroke race engine not a Buick. It's not supposed to sit there and idle on the stand while you put on your gear.


Damn Yankees
Nov 21, 2000
North East USA
I never tune my bike so it will iddle more than a few seconds. I find I get better throttle response that way. It also shuts off better when coming into a turn. There's nothing worse than chopping the gas only to have it "idle" into the turn...and over the berm :)
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