Motorcycle Repair: xr 50 wont start, honda xr50, motorcycle mechanic

Question
rich,i have a few questions for you,my son has a honda xr50 he started it up and rode it to the yard and it quit running,by the way it's a 2000 model yr.,it wont restart,it has spark ,gets fuel has a new plug,all the vacuum lines are nice,has good compression,it acts like it wants to start, but wont,my guess is timing,but i not a motorcycle mechanic,just guessing,how can i tell if the timing is out or if the chain and tensioner need replaced? i have been fooling with it for a week now,i met a guy who "said" he fixed motorcycles and he attempted to remove the cover on the left side cylinder head and could'nt get it off,how does that come off,it has a tooth on it, do u tap it off,he tried to tap it off ,by tapping the tooth forwards with no avail,any help would be highly appreciated.   thanks ,don

Answer
There's a bolt on the right side of the head that goes through the center of the cam to hold the cam cover on.  If the bike's compression is in spec, I wouldn't think it's cam timing.  I'd look for either spark timing or fuel.  Try putting a timing light on it and see if the spark timing is right.

Good luck
Rich