2000 rm125 carb

Hey guys! I’m new here and wondering if anyone has ever put a Keihin 38mm Air Striker on a 2000 rm125. I believe the original carb on the bike is just worn out. I have throughly cleaned it, put new jets and seals in and still runs rich and will not idle. Even with the idle screw all the way in. I have tried multiple settings on the air screw and still will not idle. The bike has excellent compression (150 psi). The bike was running with a high idle until I cleaned it. Now will not idle at all.


Staff member
For the carburetor you have, the idle mixture screw will be an air screw. Turning it in will make the idle mix richer, out to lean the idle mix.
Mid throttle position is handled by the needle shape or needle jet ports, and anything beyond half throttle is controlled by the Main jet size.

I'd clean the carburetor again really well, jets and all passages blown out with compressed air.
If you're more than 3 turns out from lightly seated on the idle mixture screw, and still not lean, I'd step down on the pilot jet. And start again from 1.5 turns from lightly seated. You will eventually get surging or a hanging idle from revved up. That's too lean.

If the dimensions of the inlet and outlet are correct, the 38MM Keihin could be a good swap. I have looked a the 39.5mm air striker as well for a mod on my bike. Fuel line and choke location may vary.
Remember, if you do the carburetor swap, you'll have to go through the process of tuning it correctly, as above, anyway.

-BIG DAN:thumb: