05 yz250f header pipe glowing??

Yes the carb is dirty, probably the pilot and leak jet circuits. Decel pop is a sign of a lean condition. That will get fixed when you clean the pilot circuit and adjust the fuel screw.

Was the choke on when the pipe was red? If so it was rich and excess gas was burning in the pipe. Once you get it cleaned up and adjusted it wont glow red unless you let it idle for excessive time. If it does glow red don't worry it won't melt.

My RMZ glowed red until I finished setting up the idle speed and fuel screw setting. Once dialed in I could only see a very slight red glow in total darkness.

You really need a manual. If you have previous experience you may be able to use a parts micro fiche. They do claim the fcr carb is the most sophisticated carb made, well, most expensive. The ap or pilot is the likely culprit to the glowing pipe syndrome. I do believe a dirty filter will mimic a rich condition also. Still, an O2 sensor would be the cats meow to jet with. 4t's to my limited knowledge do not have cheap plugs to jet with, or is readily available to remove and check. Seat time, throttle response and the dreaded popping are easier and cheaper. That wide band O2 sensor will set you back 250 dollars, and a crucial set up job! I have not seen any respectable reviews on the adjustable leak jet, also a bit pricey. That is a jet for the ap circuit.

and it is normal for any 4 stroke header to get cherry red when running sitting still- once moving the air will keep it cooler