I have a 04 crf250r that I had just put a new 06 head, valves, springs, stage 1 hot cams camshaft , new piston & rings and double checked valve clearences and timing and will not run. All that we can get out of it is alittle pop or fire. The guy working on it works at a Honda dealership and thinks it's the ignition. Althoe it seems to have good spark. It ran when I took it into him so don't know what it is. He also said it could bre that the carb's slider is getting wore out and is leaking??? Any help would be greatly appreciated . Thanks!!