400 ex pipes glowing red in 30 secs

[jamesleber]

Ok, I have a 1999 400ex and I had to put a new cylinder and piston in. I have triple checked the valves ( .010 in and .012 ex). everything looks good and sound good. But after I hold the trottle open about half way, the pipes start to glow red after about 30 sec. I have changed the jets, still does the same thing. I runs great except for the glowing. I am out of ideas. Please help??

This quad is bone stock. I even put the same size cylinder and piston in that it had before.


Please help???

[oldskoolex400]

it means your to lean doesnt matter if you change the jets or not if its not the right size prolly change your main jet and it should help alot

[northwest Texas]

I'm not the smartest on the carb workings but if it's at half throttle and glowing, wouldn't he need to lower the clip effectively raising the needle to richen it maybe?

The main's main range is in the upper revs and the needle controls the fuel through the main from roughly 1/4 to 3/4, right?

I'm trying to do my homework because I know I've got a lot to mess with when I get my top end back.

[Kaleigh]

sound like you're lean.. the fastest way to come close to the perfect jet.. keep going up jet sizes til you stumble at Wide Open Throttle.. your stock so i would go 150-155 then work your way down till you dont stumble at WOP.. then your jet size should be ok..

[GPracer2500]

If you hold the throttle open half way for an amount of time (while in neutral) the headers could easily glow no matter how you're jetted. There's nothing abnormal about that.

BTW, I assume you ment .10mm (.004 inches) and .12mm (.005 inches).

[jamesleber]

I have a jet reemer kit. I have now opened up the mail jets to 2mm, Still the same problem. Could I have not installed the compression release right?? Could the timing be off?


Thank you!!

[400eXr1d3rZ]

It's normal, well I assume it is. When I rebuilt my bike it ran really really hot, then once it started breaking in it ran cooler.

[heavyonthegas]

My '02 has all stock engine parts, and I did the same thing and my pipes also glowed red. Kinda startled me, but I think it's normal. I'd just never ran it that hard without the cooling air flow before... Correct me if my guess is wrong guys, but I suspect this setup is fairly common.

[Kaleigh]

Originally posted by heavyonthegas
My '02 has all stock engine parts, and I did the same thing and my pipes also glowed red. Kinda startled me, but I think it's normal. I'd just never ran it that hard without the cooling air flow before... Correct me if my guess is wrong guys, but I suspect this setup is fairly common.

could be.. but i never seen mine glow.. ill have to keep an eye on it..

[jfwyatt]

just about any air cooled 4stroke will glow the pipe without any airflow. titanium pipes are especially known for this. also were you in a poorly light place when you noticed it glowing. that just magnifies the glow.

[Honda#4]

mine has never glowed yet.