Rm250

[TM400Rider]

"Too much preload on the spring. On the left side of the cylinder is a dial that controls the spring preload for the exhaust valve system. The preload doesn't have that great of an affect on the engine's powerband, but too much preload will prevent the valves from opening, which causes a lack of top-end power."

I read this on on another site and I have a 1991 RM 250 and I need to know how to set the pre load on the spring they are talking about. Any help would be appreciated. Does anyone know if you will see a noticeable performance gain out of adjusting this? Any other suggestions on how to get more power out of a 91 RM 250 cheap? Thanks a lot

 

[overbore]

we have a newer model and it says that it should be set at one
fourth turn clockwise and the older ones were set at one half
turn clockwise.So I would think that yours would be one half.
hope this helps.
overbore.

 

[TM400Rider]

Ok thanks, How do they judge the turns tho do you turn it as far as it will go clockwise and then back it off a half turn or do you turn it as far as it will go counter clockwise and turn it clockwise? Thanks a lot.

 

[RM_guy]

I believe that year RM was set at 3/4 or 1 turn. The setting is from when the spring is in it's neutral state. Remove the adjuster knob and, with out moving the spring, replace the tang of the spring into the back of the adjuster. The position where the adjuster ends up is your start point.

Turning it clockwise will increase the tension

If the motor tends to bog when you open it up, back off on the spring tension. If you seem to loose your low end power too soon, increase the spring tension. You'll have to play with it to get the best low and top end power. The spring tension will only change when the power band kicks in. It can smooth out the transition from low to high and reduce the "hit"

 

[TM400Rider]

Is there any chance that if the knob was turned to far that it could cause any kind of engine damage? thanks

 

[RM_guy]

No, it won't damage anything.