I installed the high compression piston and jet kit (from Jesse ) my 97 650 DR and love it! The base gasket was leaking goo all over my boot, rear tire and rear disk ... left turns were a real thrill! I was forced to do something... so as long as I had the top end apart I thought I might as well get a few extra horsepower. My bike has stock gear gearing and this old scoot flat out hauls a... Really its too much (did I say that!) for most dirt riding. I just got it together a couple of days ago and have some tweaking to do, rough idle and at least one valve sounds a little loose- need to check clearance. But right now I would say the modifications has given the DR about a 10-15% gain with a whole lot more throttle response (and kinda growls just idling). This is my first post/ reply to TT. Specs: 97 DR, White Bro pipe, air box mod, jet kit, high compression piston, skid plate, IMS tank, corbin seat, Longest Ride: San Diego to Cabo San Lucas Baja MX. I'll keep interested parties posted on bike progress. newbie.