2003 Rm250 stutter issue??

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7/15/2018 9:49 PM

Okay so i bought a 2003 rm250 a while back and have been rebuilding everything on it. The bike ran really rich and stuttered bad when i first got it.
It has the V-force 3 reeds and i put a pro circuit headpipe with a r304 factory sound silencer on it.
I run 40/1 with blends all and 93 pump gas.
So far ive done what pro circuit reccomends and then some and am still having issues.
So heres what ive done so far.
Carb rebuild kit. Mainly new seals and springs.
Main jet- (stock 175) to a 165
Pilot jet- (stock 50) to a 45 then a 42 in it now.
Needle clip- (stock 3rd notch) to the 2nd slot
Slide- (stock 6.5) to a 7.0
Air screw- tried from 1.5 out all the way to 3 with no change in the stutter.

Now the only thing i havent changed is the power jet from a 50 to a 48 but i cant find a 48 power jet anywhere. Even the local dealers cant track one down.
Im thinking maybe buying the jd jetting kit and swapping needles around maybe to find a better result?

It idles great. Starts first or 2nd kick. Sounds crisp on a stand but once a load is put on it it only stutters at 1/8-1/4 throttle. And by stutter i mean it cuts out bad. Once it gets past that it runs great. But the stutter is almost impossible to ride mx without having it wfo. It cleared it up a fair mount swapping the slide to a 7.0 but its still pretty bad. Ive had 3 people look at it and try to tune it and its all left them wondering. Im at a loss for ideas and was hoping someone knew something maybe i didnt?

I took the TPS off also and made sure it had tension and cleaned it but is it possible it may be bad and causing this? Im at a loss for ideas here. Ive heard the 03 is finicky on jetting but this is blowing my mind. So please if you have any info i would love to hear reccomendations to solve this nightmare.


7/16/2018 6:09 AM

Transmission side crank seal...


Tomac and/or Anderson for 2020.....

7/16/2018 7:41 AM

Like stated above try crank seal. I have an 03 also and sent my head off to RB designs I think it what its called to get the squish cut.
I was having same type of trouble you were having but maybe not as bad Im not sure. Usually when riding I was past the rich point so it was ok but some jumps required that exact spot on the throttle and it is super dangerous, with almost cutting out.
Anyways I got the head cut and I got my slide cut to a 7.0. Between those two it helped out a ton and runs perfect.

Other thing I did is swap the 03 stock needle for a NECH needle which is the later model stock needle I think.

I am 6000' elevation and running
162 main
nech needle 1st clip (leanest)
45 pilot
stock power jet
7.0 slide

Cut head still runs on pump gas

you can read all about it here.
jetting thread


7/18/2018 8:24 PM

lcgordon711 wrote:

Like stated above try crank seal. I have an 03 also and sent my head off to RB designs I think it what its called to get the ...more

Ill look into that. Never wouldve geussed that by it sputtering. I figured it was the carb. And exactly at my house ive got 2 65ft doubles and both are either 2nd tapped out or 3rd 1/8 throttle right in the choppy section. Ive been riding my yz250 in the meantime but couldnt seem to solve the rm's issue. Thanks for the input looks like itll be coming apart again lol.


7/29/2018 11:27 PM

Have you checked your power valve to make sure it's operating right and not sticking or binding open or shut

I had a maladjusted cable on the RC valve of my CR250 that caused it to run exactly as you described yours....... it sounded and felt like it was very briefly starved for gas then it would take off and scream with a perfect crispness and note that sounded like a perfectly jetted 2 stroke should. I kept adjusting and readjusting float level thinking it just needed a little more fuel to get rid of that very brief hiccup down low until I decided to pull the rc valve cover and realized I had been a knucklehead.


7/30/2018 6:31 PM

Im going through the exact same thing as the OP. gonna have to look at the crank seals. Cant figure it out either.