a few weeks ago i purchased an 03 yz450f. i got it for what i thought was a steal. The guy said he thought it needed a head gasket because there was water in the oil(milky) I offered him $1800 for it and we had a deal. i brought it home, decided to kick it to see if it would kick thru a stroke and the thing fired right up. of course i shut it off immediately knowing the oil was bad. I did some research on forums mostly on ThumperTalk and decided i should replace the waterpump seal and bearing and if needed the shaft(which by the way looked perfect so i didnt replace it). I dissasembled the engine, i didnt split the cases but i pulled out the clutch pack to see if it was worn because as i put the bike in gear when i was running, the clutch was not fully engaging, it was creeping forward. After taking head and cylinder off, it appeared the piston and rod and valves were almost new, harldy any carbon buildup and the cylinder was smooth as glass. i poured about 5 or 6 quarts of oil thru the engine and drained as much of the white oil out as possible and replaced the water pump bearing and seals. after spening quite some time(im new to four strokes) getting the cylinder, head and cams back in and the timing correct, i put everything back to together, checked to insure the valve clearance was in spec(all 5 were) and kicked on it for almost 20 minutes. all i got was back firing, i could smell gas and i checked the plug to see if it was firing and it was but i replaced it anyway. it still didnt crank. i didnt do anything to the carb while it was off, so i dont see how that could be the culprit. i decided to give it a break until the next day so i leaned it up against my weight bench while it was in neutral and it apparently put to much pressure on the shifter because it is in gear now and i cannot get it to go into neutral or any other gear. also when i pull in the clutch it doesnt seem to engage. it is the same as if the clutch were not pulled in. I was hoping someone would have some input into the not cranking and the locked up shifter. I have a feeling that the cams may be off a tooth and it is difficult to decipher where the I is to make sure it is at tdc. also i was wondering if the the clutch could be the culrpit for the shifting problem. I believe it could be the shifting fork, i hope not, i dont want to split the case. Anyone had any similiar probs?