Anyone ever use one of these?

I saw that too and was wondering the same thing. Not too expensive and you could take it off when the conditions don't warrant it.

Used to run flywheel weights almost all the time on the 250 two strokes. 9 ounces seems alot but they usually make several different weights. They do everything the article says and between flywheel weight and gearing you can really get the 250 two stroke to suit the track.

You can acheive nearly the same results with a few adjustments that a flywheel weight produces without losing top end rev. change the position of the stator timing, adjust the tension on the powervalve, and go down on the rear sprocket -1 or -2 teeth. You can slightly de-tune the powerband but still keep the feeling of how quickly the bike revs which is good for mx. I wouldn't recommend the flywheel weight for mx because it really hinders how far the bike is going to pull down a straight section....it is more useful for woods riding where the revs are usually kept low because high rpm power doesn't work well on tight trails.

You can also add a little flywheel weight by running steel clutch plates.

Yamaha sells a GYTR weight that ends up being 8oz heavier than stock. Much easier to deal with since it is an entire flywheel and not a bolt on weight. As an added advantage it will clear the stock ignition cover without a spacer and two gaskets. I believe cost is under 100.00 from any of the online places.