oil filter cover on 03yz250f?

Best educated guess here: Sounds like the holes are stripped to me. There is probably enough thread left to provide the resistance you feel when tightening down, but not enough to keep the bolts from "jumping" the threads when they get down to the last bit. You will have to install Heli-coils or Time-serts into those two holes, or drill and tap to the next size bolt. I wouldn't ride it until you get that done. Shouldn't be too difficult for these two holes as they are readily accessable. Any garage or machine shop should be able to do this for you if you don't feel up to it. Drilling and re-tapping to the next size up would take about 15 mins. and cost you roughly $15-20 in parts from Autozone or somewhere similar (couple drill bits, couple new bolts-hardware store-and one tap). If you go that route, be sure you can drill the holes out in the oil filter cover to accept the next size bigger bolt without getting into the O-ring groove.

Using a heli-coil or similar insert would mean taking more material out of the case, but using the stock bolt size. As long as there is enough material around those two holes, it should be no problem.

I've got lots of exerience with drilling out and re-tapping, and limited experience with inserts, so if you need some more info, post here and I'm sure I or someone else can help step you through it. :thumb:

What Lou said.

Those things are easy to strip.