Just in case anyone is interested in the results from what typical mods do, here is my story. Before 1999 xr650l. White Bro's pipe (with disks), smog kit eliminated, jetted correctly, air box mods, good foam filter, street tires, supermoto fender. best 1/4 mile time of 13.9 @ 89mph. After JE piston, 10.5:1. Hot Cams Stage 2 Cleaned Intake/Exhaust Ports, combustion changer etc... best time of 13.2 @ 95mph. Weight with me on it is 495lbs as measured at track. Jetting seems to be a little lean with the new combination, a carb is a definite mod for the future, as well as intake porting. It feels great, although I think with the current carb and port combination, a stage 1 cam would have been a better compliment, as it wants to rev out, but kind of hits a "wall" on top. I think the clutches started going out, as my first run of the night was my best, after which the shifts started feeling mushy, not solid engagement. It is the original clutch with a shit ton of hard miles on, i was quite surprised it has lasted this long to be honest. Important to note, starts like shit, barely turns over without the compression release. If jumped it starts great though. So there you have it, truly just "bolted in" the mods, and that is the difference. I would highly recommend the piston to anyone, and if you want a fun wheelie machine maybe the stage1 cam instead.