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400EX Symptoms... Need help.
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Posted by: rYan01400EX

Here are some symptoms my problematic hunk of junk is causing..

1. Backfires on deceleration. Running rich?

2. It gets so hot, the headpipe starts to burn my leg under normal riding conditions... This is NOT normal..

3. In first gear, when putting along about 1/4 throttle in first it cuts out, misses, pops... but when I stay into it, it does fine.

Here's what I got:

ENGINE: Wiseco 406cc 11:1 piston, Full Big Gun RACE series exhaust
CARB: Dynojet 165 Main, 38 Pilot
ELEVATION: +513 FT

Posted by: mcleod

i would raise the pilote, and try ajusting the fuel screw / jet needle.

Posted by: F-16Guy

Backfiring on decelleration is almost always a lean idle (pilot) circuit. Also, make sure you don't have any obvious exhaust leaks which will aggravate the backfiring problem. It sounds to me like you may be too rich on the main jet and you're definitely too lean on the pilot jet. You should have at least a 40 pilot with the fuel screw about 2 to 2 1/2 turns out.
Try:
160 DJ main
DJ needle in 3rd groove from the top
42 pilot, fuel screw 2 1/2 turns out.

That should cure the backfiring and red hot headpipe. If wide-open-throttle (WOT) gets better with the smaller main, go down another size. If it gets worse or stays the same when you do that, go back to the size you were just at. If it keeps getting better, keep going down until it doesn't.

Posted by: CarGuy7a

definately sounds lean. excess heat usually means lean.

depending on what mods you have done to it a 42 will be way too much. i tried a 42 in mine and it was so rich it wouldn't even start it just flooded out. i ended up putting a 40 in it with what mods i have and it runs fine.

Posted by: CarGuy7a

duh sorry didn't read what you had done to it till after i posted that.

yeah you prob could run a 42.

Posted by: rYan01400EX

With a 42, I suffered the same problems as you CarGuy... I'll give it a shot with what F16 reccomended.