Check your WR450F rotor / stator retaining bolts as I recently had the misfortune of them coming loose on my 9 month old bike, which in turn demolished the stator, rotor, crankcases, starter journal etc. (Originally I had the woodruff key sheer within 100Km of running the bike in when new. The woodruff / engine was repaired & checked by my dealer & the bike ran OK (but noisy) for a further 800Km. It was in again twice after to investigate a "loose noise" but again nothing was found. To my amazement 3 days after the last check my engine failed due to a demolished stator etc caused by the retaining bolts sheering / slackening off. The cause of this? not being torqued up sufficiently / bolts being long enough. When this happened 3 of my mates with 03 WR450F's had loose stator retaining bolts also when they checked their WR450F's. My local dealer confirmed that I was not alone with this fault & they said that Yamaha knew about it but would not accept this as a design fault. The remedy is to use longer stud bolts, loctite them & turn the heads over (pancake the screwed end) to avoid them slackening off.My bike cost £600 parts & £400 labour to rectify. I am currently trying to get Yamaha to acknowledge them blame for this & cough up for the repair. If you know of this problem, please e mail me.