Hey guys...i have a weird problem going on with my 05 450. I bought it new in 05 and first thing i did was put a iron man rear sprocket +2, x-ring chain with front sprocket spacer. It has been running great for 05, 06, 07 and then just recently i was at Forrest Hill riding and the front sprocket fell off the shaft. Luckily we just got done with the loop up by China wall that is supposed to be the most "technical" trail in CA. I bought a new bolt and washer that holds the sprocket on the shaft and put it on. I was down in Jawbone over the weekend and the samething happend to me!!! It's reverse thread so shouldn't the bolt snug itself rather than backout? I am going to have to start carrying a spare and tools incase this happens where i can't get a truck to! As always....any info. is much appreciated! thanks!