2002 Rm250 idle problem (sudders)

[SnowX51]

Well i just rebuilt my rm250; put brand new piston kit, bearings, seals, gaskets, the whole works. Now it seems it idles really rough or "studders". Now i checked everywhere on the boots and no cracks. I'm not sure if there is a airleak in the crank; but i would have thought if there was it would either be burning tranny oil, pissing out oil/gas through the gaskets. One other thing is that once im at higher rpms or powerband, it runs fantastic! Anyone got an idea?

I made a video on youtube of it, just so you can hear what im talking about

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[SnowX51]

im wondering if it has to do with the cdi box. Anyone got suggestions?

[Freak]

sounds like the timing is off.

[Fluffyhead]

I have the same year model RM 250 and had issues with my rebuild as well. I bought it used and rebuilt her from soup to nuts. If it were an air leak from the carb side, you'd hear the engine rev like it was going to seize. If you spurted excessive oil it could be an incomplete seal of the crank seals. A leak on the flywheel side seal might also give you a screaming over rev on kickover. Did you take apart the carb and really clean every jet and orifice with carb cleaner? I went on to ebay and scored a 'Moose' carb rebuild kit for under $30 delivered which included all of the jets, o-rings and gaskets to freshen things up. I had to play with the air/fuel screw but wound up close to the 1.5-1.75 turns out from fully seated recommended in the Clymer manual. Then it was a matter of dialing in the idle screw.
Curious as to what premix your using and at what ratio. Love to see more video of any progressive steps and there effects.

Peace,
Sean