I just got a 2004 WR 450. First on my todo list was to change the oil. When I removed the lower bolt on the oil filter cover I noticed there was no o-ring like the manual said should be there. Since no oil came out of the hole, I replaced the bolt, but it would not tighten up. Upon removal I could see that the threads were stripped out. Can this be retapped to a larger bolt size, or do I need to replace the case? If it can be retapped, how do I keep the metal filings from getting into the oil system? Also, if the manual says to remove this bolt as part of the oil removal process, why did no oil come out?