400ex carb info needed

[gtivdubdude]

I need someone with good, hands on info on this Question. I have a 2001 400ex and I have just put a 426 kit in with a stock cam It has full yosh exhaust, K&N filter and I have changed the main jet To a 50 (stock is 48 I think) I have not started this bike Because I want to make sure i have everything Just about right. Any info? I know when it was stock it had everything listed (exhaust filter, and jet) It would backfire bad untill it warmed up and then it ran like a top. I was told that i should change the pilot jet to a 40 (38 it stock?) Anyone with some info would be great.
Thanks

[K_Fulk]

Ride it and see how it runs. Might be good might need a little more. Thee all a little different.

[gtivdubdude]

Well I got the engine running tonite, and it seems to run fine. I wanted to ask, If the engine was gonna smoke really bad or something really freak like that would it be doing it already? I know when i built it The book said to be careful with the rings, and i was careful as I could be But the oil rings were a pain in the butt to get into the cylinder, I (very carefully) Used a small screwdriver to push the rings into the piston groove so i could get it to slide into the cylinder. Does this sound ok? I know i did not bend them or anything. And I thought if it were gonna have a ring problem (like severe smoking) I would see it right off the start. It ran for about 15 minutes or so and everything seemed fine. Any info would be a big help!
Thanks

[yfz450admirer]

I have a 440EX that is five years old. The guy I bought it from ran a 185 main jet at 2000 feet above sea level. I have tried various smaller jets, but always return to the 185 for the best performance. I would definitely run a richer jet. I have friend/mechanic that runs a virtually stock 400ex (piped) with a 172 main jet. A larger pilot jet is a good idea and richening the needle one notch. Good luck!

[Jonas]

There must be a mistake in the jetting specs that you quoted. Can you tell us where your at right now again to clarify. Main jet, needle position, and slow jet?

[Jonas]

Did you go from a 148 stock main jet to a 150? If so, you are too lean on the main and it will probably hesitate on full throttle.