I bought a 04 kx250f(Brand New-Never Ridden) Bike ran fine from dealer. It did have a little pop to it so I went and purchased a srp mixture screw. When I took out the old one, the screw , spring, washer and o-ring came out. I lost the o-ring and washer (whoops). Well I wanted to ride so I put the spring on the screw and threaded it in. I brought it 2 turns out and with a few kicks it ran. I went in the house and put my gear on and went outside and about a 100 million kicks later NO START. Are those two parts so critical to make it run(o-ring,washer) or did I possibly screw something up in the process of putting it on. The thing I cant figure out is I let it warm up without the oring and washer. I shut it down then 10 minutes later nothing. Either way I'm going to get the oring and washer. I just have a feeling when I put those in I'm still going to have the same problem. I checked the plug and it looks fine. I even tested for spark and its fine. Got compression and a clean air filter. Hell, its only a few days old. I live in Michigan close to sea level and 40-50 degrees (F). Jets are stock. This is the thing, I rode it for about an hour when I got it just braking it in. No problems until I messed with the air screw. Just cant figure out why it ran and then didn't. Any help would be great.