TM 250mx with flywheel weight

[Kinna]

I'm coming from a 1979 250 mx bike to hopefully a 1999 TM 250mx. I know the TM is going to be something totally different but what are some other ways i can tame it besides a flywheel weight. and what exactly does a flywheel weight do except help prevent stalling (i've never used one) Oh and please dont recommend me getting a 125 instead because this is a great deal on this bike.

 

[MikeS]

The TM250 will pull good down low and into the mid range like most 250's then it just has a surge of power and over rev.

I would look into the flywheel as it tames the hit some plus allows better for low speed control (stalling is eased some). You can change the cylinder base gasket to a thinner one, just use good fuel as compression will go up but low end to mid range is helped. Shorting the silencer or finding a shorter one will kill some of the over rev. Jetting can be the most time consuming but if you use "good" fuel and take the time to jet the low and mid range correctly then the power will be much smoother. Lastly you can add 1 or 2 teeth to the rear sprocket to tighten up the gearing as this will help keeping the bike in it's sweet spot.

Good Luck

 

[TM-Frank]

Against all theories I found the 250 a lot easier to ride without the flywheel weight of the lighting system.
You could install the lighting system from the enduro version. That means a aluminium flywheel with magnetos in it, a wider cover with the coils installed and a different nut for the crankshaft.
But like I said I didn't like it. Although the engine was a bit tamer down low, it was extremely hard hitting once it reached a certain rpm-level.
Boyesen dual stage reeds help a bit. Rejetting necessary of course.

 

[bte]

You can also switch out the carb 39/38mm (I can remember) with a 36mm. That seem to help my TM out the most (when I still had it). But, the jetting took some time to get right.

brown

 

[Henk]

I'd ride it without the weight or any modifications to start with and see how you go. It could be you are trying to fix a problem that isn't there. I've put flywheel weights on a couple of bikes (a 97 KTM 360sx and an 02 tm 250mx ) and to be honest I didn't notice much of a difference. Could be my lack of talent of course.