well i have a 400ex and today i decided to go riding and it was wet out so i decided to put my air box lid back on. well i got on and started it up while i was warming it up i looked down and my headers where beat red on the verge of melting so i shut it down and let it cool of i took the lid back off and i didnt glow and with out the lid it back fires on deceleration but only when the motor is cold my question is what do u think is wrong why does it glow with the lid o i kmow its a low end jetting problem so i can fix it my self but i dont know whats wrong please help if you can thanxx

 

Certainly sounds like a timing issue. Combustion seems to be taking place even during the exhaust cycle. I'm no mechanic, but that would be my guess... especially with the back-firing.

 

Too rich!

 

mt dad is a machnic and it is to rich its like this when the header is hot you go to slow down there is to much fuil in the cylinder and so we you back of it all the ral gas does not burn up on the comp stroke so it goes out the exohst and there is not enought presser out the exohst so the ral gas sents in the header and the heat is hot so it combust and for the timeing i would go to a dealer or someone that knows about how you need your timeing set for your power

 

sorry did not pass school in spelling

 

well i know its not the timeing because i rebuilt the motor in august so im not worries about it i know when i put the lid on it had less air so it got rich but i thought that when something is rich it runs cooler? am i wrong?

 

Well pull your plug that way you will know if its rich or lean.

 

Deffinitely to rich. A friend of mine had a 400ex with DMC dual barrel exhaust and is was running way to rich and his header did the same thing. It even melted through one of his boots!!! WAAAYYYYYY to HOT!

 

I just got a brand new 2001 400ex a month ago, it only has about 10 hours on it. My headers glow also. There is nothing wrong with your quad. The faster I go, the lees it glows. When I go slow or at idle for long periods, they are bright. All you have to do is drive it like you stole it, they dont glow as much.

 

well my plug is dark black even with my lid off so it must be rich in the low end ill lean it out enough so i can run with the lid for the snow or do u guys think i should leave it off for the winter thanxx for all the help