very hot and backfire after rebuild

[D3structive]

I tore my bike down at the beginning of summer to a pile of parts just to see how everything came apart and goes back together. it sat for almost 2 months and finally got it back together last night. put fresh oil in and fired her up only to see that its getting very hot very quickly. Im running a white bro slip on with k&n jets 42/152 I know my main is a little lean but the riding i do is mostly 2nd and 3rd gear. either way before I tore it down it was running just fine. So i fired it up let it idle for a minute and shut it off when I saw the beginning part of my headers starting to glow bright red!!!!!!!! I did not open up the motor and when I hit the kill switch it shut down, backfired and a flame came out of the pipe. any help would be greatly appreciated as I would like to go riding today. I did replace the header crush gaskets with brand new ones by the way. No air leaks either I already tested. other than the slip on and filter the bike is completely stock.

[DragonGunner]

Yes you running way lean....air mixture screw needs adjusted I would say, an as you said a bigger main. Not getting enough fuel with the air coming in Could raise the needle a notch also, also if your carb sat long enough the gas in it could of varnished an clogged things up, carb cleaner to the inside of carb...if your running air box lid off put it back on to cut down on the air coming in to richin it up...just some ideals.

[punk rock kiel]

its getting cooler so the header is gonna heat up and glow more at idle cause your not moving. i just checked my jetting cause i got a bung in my exhaust for AEM wideband gauge and its sitting nice at high 12s at idle and my pipe was glowing but mines a thin wall stainless sparks exhaust.

[D3structive]

you didn't at all address any part of my problem...

[xtreme762]

Seems to me that you should be running bigger jets. Especially with a slip on and K&N. Where in New Jersey are you? What elevation are you at?

If you didn't tare the motor apart then timing shouldn't be an issue. But I would check it anyway, just to be sure.

[punk rock kiel]

oh cause you listed all what you did to your motor upon rebuild and that helped alot. when it gets cooler, of course the header is gonna glow. your pilot is plenty rich for any work done to a 400 and your main is prolly lean.
but your from jersey, so you know it all already, so why did you even post???

[powerbomb400]

Like others said you are running lean. Cooler weather you will start running richer. There is more oxygen in the air when it's cooler. Anytime you increase air flow you will need to rejet. Take the jets out and clean them good. Check the small holes and make sure they are not stopped up. If you run gas with ethanol it will attract moisture and stop the carb up.

[JOHNDOE83]

Yes, like everyone said its lean somewhere more then likely the pilot and the main deff needs a lil more.

Headers should never glow red, my 440 doesnt even glow red, thats a sign of being to lean.

Its also possible you have a air leak.

[DragonGunner]

Originally posted by powerbomb400
Like others said you are running lean. Cooler weather you will start running richer. There is more oxygen in the air when it's cooler. Anytime you increase air flow you will need to rejet. Take the jets out and clean them good. Check the small holes and make sure they are not stopped up. If you run gas with ethanol it will attract moisture and stop the carb up.

Cooler air is denser, denser means more air which is going to lean things, not richin. On mine with a 180 main an open box it starts running bad in cold winter conditions, I just through the lid on an it cuts the denser air an richens back up to run good, easier than changing the main.

[D3structive]

found the problem....partially clogged pilot. I just replaced the pilot with a 42 a few months back and assumed it couldn't be clogged, also just bumped up to a 158 main shes running nice. thanks guys