I Need Help!

[tristan18au]

hi i oen a 1998 XR250 and it RATTLES!,and evan worse when it gets hot. what could it be? the valves have been adjusted spot on and the rings are ok and it is not burning any oil.could this just be wear or the cam chain??
also the bike runs on super petrol and has a staintune muffler and has been jetted right.
also the bike gains compression when hot> could someone please help me????:( :( :(

 

[snaggleXR4]

If I'm not mistaken you have an automatic cam chain tensioner. Either your tensioner has quit working, or more likely, you chain has stretched and is rattling around. You might just triple check your valve clearances, to be extra sure.