'05 CR125 Air Screw and Idle

Just picked up the bike yesterday, bought it off craigslist for $1650 and the idle on it was way up there (let out the clutch without gas and it wouldn't stall haha).

I think the guy had the air screw (screw with the lock nut right?) at about 3 turns out, i turned it in and put it at about 2 turns as a starting place and it idled very high. Backed it out a turn and started it until i got it where i liked it, 6 turns out.

I think i read you should only go 3 turns out until you need to change your pilot jet or is it alright to run it at 6 turns out? I haven't looked to see what jets are in it yet and i've never messed with a 2 stroke's carb, so please inform me.


Edited by honda53

Thanks, very helpful link. since i just got it i think i'm going to drain the gas and put my premix ratio in and see how it runs. then i'll go from there.

I just put a Tiny Tach on it and it's idling slightly above 1400rpm (and this is after i got it down haha), what should it be idling at?

Alright, just had to take the carb off to get to the jets, its got a 55 pilot/slow jet in it. while i had the carb off i cleaned it up a little and found another screw kinda below the choke knob, it was at 1 1/2 turns out. i put the screw at one turn out and the idle dropped down to around 600rpm (about right?). Also, im not sure if it was because it was getting dark outside, but the exhaust started looking white, thats when i killed it and want to see what you guys have to say haha.


Which screw is the air screw and how many turns is it supposed to be out and how many can you go?

Which screw is the one below and kind of to the right of the choke knob (#7 in the link) and how many turns out is it supposed to be?

Parts fiche link:



The phillips head idle screw has the locknut, the airscrew is the small brass flat head screw.

If you want your bike to idle you just turn it clockwise to increase idle.

The air screw richens or leans your pilot. Clockwise to rich counter to lean. If you reach 3 turns out counter clockwise from slightly seated and it is still rich off idle, you need a smaller pilot jet.

Ok, thanks that staightens things out, I was thinking the idle screw was the air screw and that I was going way too far out :ride: I guess I shouldn't trust random threads off google.

Thanks :ride:

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