Ok now the title is way too vague, let me explain: 2007 rmz 450 I got for my boy had a blown head gasket. Looked like bad water corroded gasket and it gave out. It sat for almost a year then we rebuilt carb and put it in a ziplock bag. We then took head off and replaced gasket following all you tube directions. Lol, now I do have a decent amount of dirtbike mechanic experience and I’m aware that if something can go wrong it definately will. I been riding and working on bikes for over 30 years. So after replacing gasket and assembly , added a gallon of 110 octane fuel. Was told it required high octane and I could not run pump gas. ? I rode bike before head gasket went and bike was strong, fast . So I never questioned need for increased octane. Higher octane= less chance for premature ignition/ pinging. Anyways bike started after several kicks, hard to start, and bike ran for 5 min kinda noisy (I could hear valves a bit more than I thought you should but disregarded) rode bike down street and it was popping a lot but seamed to be clearing up. Shut bike down to check radiator level and restarted bike. This time bike ran blubbery and wouldn’t pick up rpm’s and no amount of throttle persuasion or anything would get it to “clear up” so I shut it down. We checked something’s, plug, oil, and went to restart bike. Bike will not start again. Can’t even get a back fire or a hiccup unless I take off the airbox/ air filter. Twice I removed airbox and got a pop when I kicked it. Both times I reinstalled airbox and then tried to kick the crap out of the high compression beast, not one damned sign of life. I have checked timing and inspected cam journals, drained carb, and let it hang out with my kx450 for a couple days. (Maybe kx could get it to come back from dark side) ? What the hek could it be? Help please?

 

I’m gonna rebuild carb and see if that works