My 1989 xlr250 (same motor as 91-94 xr250L, etc) recently developed a bad ticking. Initially attributed it to valve clearance, and planned to adjust at next oil change. Anyway, It got progressively worse the last time I rode to the point of power loss on the last few miles home (I live up a ~2000 v. ft hill). Felt like 50% less torque. Barely made it back. It wasnt SUPER loud at that point, but after I shut if off, looked over a few things and restarted I had to shut it down immediately because the noise was VERY VERY bad. I put in a 280 kit last year, and noted that the timing chain was worn (wedge in tensioner was very low). I've ridden about 500-1000 or so miles since then. I understand that sometimes these things can be caused by the decomp hitting/wearing out or w/e. Perhaps the spring on the cam chain tensioner broke? I should also note that I recently over heated the bike (left it idleing unattended for 20-30 mins, to the point of smoking from engine). I dont remember if it initially started ticking before or after that, but do remember it running just fine (or "normal" ie. how it ran before it over-heated) afterwards. I have not pulled the valve cover off, but noticed some awfully metallic looking oil around the decomp (it has a light leak there). I also heard that the chain/cam can rub the valve cover. What causes this? Anyway, I am just looking for what I could possibly expect once I pull the cover off. Best way to describe the noise would be pulling a bicycle chain over a right-angle metal surface, but I may be biased since I'm leaning towards the timing chain being the problem. Should I expect both of the plastic tensioners (i think they are plastic, right?) be totally trashed? Anyway, thanks for any insight you can offer and I'll likely pull the valve cover soon.