so im having a few concerns about the 09 crf450r. im looking at a used on, but worried about the decomp pin and was reading about the bottom end going out. the last 4 of the vin is 5217. as i understand it it is a vin thing. would i be ok? also what is causing all the lower ends going out? something about fuel in the oil??? how is it getting in there. i also read about filtering the fuel. so i ordered a kleen filter for the jug.