Ya know, I resisted the urge to slap on a flywheel weight for several years, even though a lot of the competition had seen the light. However, earlier this year, I was setting up a bike for an older friend of mine, and suggested a flywheel weight because of the improved starting attributes. As a side benefit, I got to slap it on my bike for a few week.

Wow, what a difference! It never came off my bike, as we just purchased another weight for the original intended user.
After more than 6 months of lots of riding, I consider it a must for most KX500 riders. Add the other basic changes noted else where on this site, and you have bike that is a true joy to ride.....
Rick