Need help on 97 RM80!

Hi, all I'm new here and could really use some help. We got a rm80 that will fire but will not kick start. If you roll it it will start but wont stay running. When you give it gas when you roll start it, it sounds really bogged down and will just die. Does this sound like it needs the top end rebuilt are could there be some other problem. Well will look forward to any advice I can get thanks.

No dont have any way to check compression. I was wrong it wont even start. But it does fires good. Just trying to try all our options before taking it in to have the top end rebuilt. Thanks