YZ250f starting and idling/overheating problem

[Rocked250]

I just bought a 2001 yz250f and it is pretty hard to start. gotta kick it many times almost flooding it out before it fires up. After it fires up it will not idle on its own. and back fires up when it reves up. not bad but crackles pretty decent.. Then I noticed the header gets a little hot. So I started messing with the air fuel mixture screw. I got it to idle and purr nicely and most of the backfiring is gone and starts easier. But now the header starts glowing orange from the head almost a quarter way up the pipe in less than 4 seconds..

bike is supposed to be stock except the air filter and the fmf exhaust an header an does have a new carb on it.

This is the first dirt bike ive owned since I gew up on atvs.. addicted to the two wheel world..

 

[Okiewan]

It's normal for a modern 4-stroke head pipe to glow.

 

[Rocked250]

ive seen them lightly glow just out of the head before. but I didn't think over half of the pipe would glow orange almost all the way back to the muffler??? im sure if I poked it there would be a hole in the pipe.

 

[Okiewan]

Can't say I've ever seen one glow all the way back to the muffler ....
Happen to be night/dark when you saw this?

 

[Ol'89r]

If there is no air flow around the pipe, it will glow red after a couple of minutes of running. If you ride the bike, the glow should go away. If it doesn't you have a problem. If it were my bike I would remove the carb and clean it. Remove all of the jets and be sure to clean the bottom of the float bowl and accelerator pump assembly. If the bike still pops and the pipe still glows red, you may have a bad or tight exhaust valve. A leaky exhaust valve will cause the problem you describe. Check your valve clearance and then do a leak-down test to insure you have good compression and good valves.

 

[Rocked250]

No I havnt rode it since it started doing it. But does have great compression and when I noticed it getting this hot was in the daylight like I said it passes red an starts going orange within 4ish seconds.. was just a little scared to get on it an ride..