Folks, I am sorry, my first quad. I changed the spark plug in my 400EX, it is a 2003. My brother screwed around with the jetting on the carb and now when I fire it up the pipe turns smoking red hot in about 30 seconds. Are these two correlated or do I have a serious problem. Any help would be appreciated.
tom

 

what did he do with the jetting?

if they glow at idle, you need to go and look at the very bottom of the carb and you will see a bronze fuel skrew. you will use a flat blade skrewdriver and you need to turn the skrew out. try 3 turns from lightly seated.

 

Spark plugs dont create heat...they remove heat. So that isnt the problem.
Sounds like your bro made it too lean...did he remove the air box cover too?

 

sounds like he jetted it to get less fuel id go up a few jet sizes and see if that will do it for you.

 

Sounds fishy, if it gets hot that quick you better check the oil! Stop turn it off, no way it can heat up that fast with just idle or even the idle screw the motor has to have some minor or major malfunction. Hope for the best for you, please let us know what you find out.

 

Mine did the same thing straight from the dealership. The carb was a bit lean to begin with from the factory. The mechanic at the dealership warned me that the pipes may glow red if it was left idling too long. So, I started it up and let it run in my driveway....sure enough those things got red hot. I bumped up my pilot jet one size and turned the fuel/air mix screw out 3 turns from fully shut, and it never happened again. It's not a big deal...you're just jetted too lean on the bottom end. 10 bucks and an hour or so will fix that.

 

Whew friends, if your Quad gets that hot you better get ready for a piston melt down or warped head and you better have some good oil in the motor. For that pipe to get red hot it's to the point of parts getting warped and motor locking clean up. [img]i/expressions/face-icon-small-frown.gif[/img]

 

No doubt that it's a sign of lean jetting\mixture at idle speed, or too high an idle speed, or extended periods of idling or idling around at very low speed. However, this is fairly common behavior on Honda's air cooled ATV's. I've seen many do the same thing. It's not very noticable except in low light conditions. It doesn't necessarily indicate it's ready to come undone. Now if it does this at cruising speeds, You do have a potential problem. Ask your bro what he did, It may be he just turned the idle speed up, or messed with the mix screw, which can be easily readjusted.

 

Folks,
I went back and re-adjusted the air/fuel mix screw. That was the problem. It is fine now. I never let it run for more than two seconds after it turned red, so I didn't melt it down thankfully. I swear those engines are bulletproof.
Thanks for your help.
tom