1999 400ex pipes getting glowing red hot.....Help?

[jamesleber]

I just had to put a new cylinder and piston in my quad. I also replaced the timing chain while I was into it. I got it fired up after final adjustment of the valves. It runs great!! I let if warm up and I road it a little, not overreving. Stopped it and reved it up to about half throttle and held it there to see how the motor sounds. Sounds great, but after about 30-45 secs, I noticed the pipes were glowing red hot.


Any one have any ideas? I am relitively new to 4 strokes, I have had 2 strokes and worked on them myself for the last 10 years. I think this problem is probabley an easy fix for someone who is familiar with the 400ex. I just am not.


By the way, My 400ex is completely stock. no pipe or jetting has been done. It is my wife's bike.

[sburton1]

probly running lean throw a bigger main jet in her

[jamesleber]

Will that keep the pipes form getting hot? It is the sames size piston and cylinder as b4. If so, how much bigger should I go?

[sburton1]

well id just go up 1 size and see if thats any better ill pm you with a good web site to buy jets.

[Stonewall 61]

You sure the timing is 100% correct?

[krt400ex]

Originally posted by Stonewall 61
You sure the timing is 100% correct?

ya, cuz if its not that could cause it to run hot. but if it is that advanced then i don't think the bike would even run. i would try jetting. how does it run?? does it studder or stumble or does it backfire on decel??? r there any strange sympoms that might not have been there before???

[jamesleber]

no, is runs and sounds great other than the pipes getting red hot.

[jamesleber]

Also, when I was putting the motor back together, I broke the feul line, I replaced it with regular straigh line and had to make it longer to keep it from kinking. The line is now about 8" long with a loop in it to keep it from kinking.

Would this cause the problem that I am having or would it be the jets like I am now thinking might be the problem?




Thank you for all the help

[Stonewall 61]

pull the plug and see what it looks like......
check out this site..... VERY good info and will give you the ability to determine lean or rich or timing.

http://www.4secondsflat.com/Spark_plug_reading.html

[krt400ex]

Originally posted by jamesleber
Also, when I was putting the motor back together, I broke the feul line, I replaced it with regular straigh line and had to make it longer to keep it from kinking. The line is now about 8" long with a loop in it to keep it from kinking.

Would this cause the problem that I am having or would it be the jets like I am now thinking might be the problem?




Thank you for all the help


is the inside diameter of the line the same as the old one??? cuz if it is smaller it will restrict fuel flow, causing the bike to run lean....otherwise, i dunno. it is obviously getting waaayyyyy too hot.

[am_muscle]

I had a yz426 that did that and was worried about it then I read in Dirt Rider on a yz426 it means the jetting is right on. That could be true of your 400. Mine only glowed red when it was gettin dark though, I couldn't see it during the day, I talked to other people and thiers did it too.

[krt400ex]

that is cuz they come a little lean from the factory.


if ur bike is glowing at night, then u rn't that lean..... only a jet size or 2

[bmurray]

LEEEEEEEAN !

[johnsls]

Not for nothin but,, replace that stupid hose you put in there.. just goto honda and but the S shaped one. Its like $5.00 at best.

Something should NOT be messed with especially when stock is so cheap.
just my 2¢