What year?
Doh. That would have been helpful. 1998.
Jumping time as in cam chain needs to be replaced, cam chain tensioner in question, cam chain sprockets suspect?
That I do not know.
Are you willing to perform a diagnostic on this problem and spend the $ to repair it?
As far as diagnostic, I have no problem with that. Money to repair....depends on how much it will cost.
First dirt bike?
Do you have anyone to ride with, anywhere close by where you live to ride it?
Yes to these. My only hesitation in this matter is that it's not street legal, and I wouldn't mind being able to ride to some of these spots.
Also probably important is I doubt he has a title for it.