I purchased a 155 & a 158 main jet, plus a 68S pilot jet today for my '93 XR600R. I have been reading about all of the uncorking mods for the XR650R, but can not find anything specifically geared towards the 600. I will be running a Hot Cams-Cam, and a factory exhaust. The guy I bought the bike from has already removed the baffle, end-cap, and spark arrestor. The header is stock, but I plan on purchasing an FMF stainless header, and slip-on later on. Do you think the 68S will be okay? Which of the main jets should I try first? Are they within useable range with my set-up? If it matters, I am at sea level.. Well, in Houston, I think we are about 20 ft. above sea level. The bike is not here yet. Once it gets here I will confirm whether or the not the air box has been opened up. If not, I will take care of that straight away. The bike already has a K & N air filter on it. Are there any mods that I need to make to the insulator? What about drilling the slide? Is that something that is 650 only??? I have been reading about drilling the 2 off-center holes out on the slide. I have heard that removing the extra welded metal from inside the head pipe is a good step. I will try that until I purchase the after-market header. What type of power increase will the aftermarket header & slip on give after the cam, airbox, and jetting mods? Any insight or advise that you can offer would be greatly appreciated!