1997 RM250 no idle

[stillife9796]

I just bought a 1997 RM250, had sat for 2-3 years. It won't idle and at low RPM is bogging down, very eratic, like it trying to clean itself out. When it does clean itself out at high RPM it runs great but then won't idle and runs very bad at low RPM again everytime.
Here's what I've done so far:
1. Drained old fuel
2. Filled with fresh fuel
3. Replaced air filter with new oiled filter.
4. Drained crankcase and refilled.
5. Removed carb and cleaned thoroughly, jets are okay 172 main and 45 pilot.
6. Replaced spark plug.

Air screw is 1 1/2 turns out (good).
Idle screw is bottomed out all the way in (spring is compressed all the way) This is how it was when I got it.
Spark plug is pretty brown almost black and somewhat wet.
Bikes starts easy enough, no problems there.
Any ideas would be great !!! Thanks.

[the_privateer]

first set the float How To Set Your Motorcycle Carburetor Float Level (more commentary).

and it sounds like you may need to drop a size or two on the pilot and if it still bogs on the way to the powerband, raise the clip on the needle one position. if it starts cold with no choke, that is a sign of rich jetting

I think the idle screw is set not to idle when it is all the way in, some riders, especially racers, prefer their bikes not idle. try backing it out to see if it bumps idle up. I could have this part backwards, but it wouldn't hurt anything to try

[artistic_gore]

Have you played with the idle screw at all? I'm not sure what you'd accomplish but to me that sounds like the first step in troubleshooting. It sounds like you are flooding slightly, how's your needle valves tip look? Have you tried adjusting the needle valve to lower the fuel height in your float bowl? Sorry if none of this helps just things I would try in that situation.

[Henry]

on my 97 RM 125, the idle screw turns in to make the idle faster becuase it pushes the slide up slightly. so backing it out would lower idle.