My old 400 ex (now stolen), was about 10 months old. RIght before the bike was lifted I noticed one night when riding the header pipes were staring to glow bright orange -red. This would happen I d say while holding the throttle open to about 5 grand or better. The next day the dealer said that it could be a tight exhaust valve. So i adjusted the valve and noticed it was a little tight, apprx. .002-.003 off. The bike still lit up the pipes when I fired it up. Has anyone else had this problem with their EX???????????? I never got to correct the problem but the @sshole with my bike had to deal with it!

 

Well, if you are too lean, the pipes will get really hot. When I bought mine, the head mechanic at the dealer said that since the 400ex has single-walled head pipes that it isn't uncommon to see them glow at night. Mine did the first time I started it up when I got it home. I installed a jet kit and it's never glowed since then.

 

The first thing I thought too was that it was running too lean. But i didnt think that the pipes would get that hot because of it. I'm curious to see if my new 400 does the same thing.

 

EX1

Was the machine running well when the head pipe was turning red? My buddy's ex was running really rough while we were doing some maintenance after he bought it used. We were running it in the garage (on jack stands) and noticed the header pipes glowing. The machine was running really rough and loading up. The culprit was a dirty air filter (we hadn't got to that yet) which was causing the machine to load up and burn excess fuel off in the header pipe. Made the header pipe glow real nice. We cleaned the air filter and it ran great and the header stopped glowing. If the machine was running good, it was probably on the lean side which would require you to rejet to correct the problem.