I have a 400ex today when I was changing the main jet the long shaft that the main jet screws into came out also. I noticed when I put it back in that it had a small nut on it that locks it in place. How far is it supposed to be screwed into the carb. Just looking at it I would think that if you screw it in to far you will raise the height of where the main jet would set, at extended lengths of riding at full throttle wouldnt this cause a lean condition.I was thinking that maybe it would suck the fuel down below the reach of the main jet.Where is the factory setting or height that it is supposed to be set at or does it matter.Should it be screwed in until it is seated then locked down, if so why would it have the small nut to lock it down.

 

I ran into the same problem last weekend. When I called tech support at Dynojet, I was told to screw it all the way down and then tighten the lock nut. I did and it seems to be fine.

Hope this helps.

 

Thanks for your help I was told the same thing from a Honda technician today .Your assistance in this matter is much appreciated.
THANKS!!!