So I have been having a lot of popping on decel on a 1999 YZ400f that I just bought a month ago. Won't idle either, with the idle adjuster all the way buried. I purchased a MSR red fuel screw for easier adjusting, on the recommendation of the local mechanic. When I dropped the stock fuel screw out, I got the spring and washer but not the o-ring. I got the remainder of it though. About 1/4 of it. Hmmmm, no o-ring with the MSR screw. Dammmit!!! I already know my local dealer doesn't have the o-ring, because I asked for one when I bought the MSR screw. The parts fiche looks like you have to buy the whole screw/spring/washer/o-ring to get just the o-ring. $30. :banghead: So, anyone have any tips on where to source a similar o-ring other than the local Yamaha dealer? And why won't my new red MSR fuel screw go into the hole in the float bowl so I can thread it into the correct location? It goes in partway but hangs up. If it means anything, so does the stock screw. Hey, thanks if you can lend any help. Did I mention I leave Friday morning for a 3 day riding weekend? I might be riding a lawn chair at camp now.