[adriano.ro]

My friend has cfmoto 500,run good but in 5 minutes of idle the exhaust pipe come red and extremely hot,about 70% is red. The problem is no matter if run or is idle ,the pipe still red,and the plastic around the pipe start to melt.

The first thing I was suspecting was carburetor settings,swap one from another cfmoto the problem is the same.
Now we have also take more drastic action and we have put some new parts like:
Piston,cylinder, timing chain,cylinder head,ECU,ignition coil,water pump.

I have even changed the timing on ignition, one tooth backwards, the pipe was red but not so badly but the engine wasn't running properly.

So,we have no clue what can be. The only thing that I can thinking is the sprocket on crankshaft is out of alignment somehow.

[doug80638]

Changing the timing is NOT a good idea.

https://boostatv.com/glowing-red-hot-exhaust/

[NMKawierider]

Right. Never change the valve or ignation timing like that. Set everythingbto factory specs, then look for the issue. In most cases glowing exhaust pipes...ie more then usual that is...is caused by first an extreme lean fuel condition, then by an extreme rich fuel condition, then by leaking exhaust valves or even the exhaust pipe seal allowing O2 into the inside, then by a buildup of carbon on the inside from the burning of oil that collect heat and causes the glowing. I have also seen very old and nearly rusted through pipes glow as well cause of how thin they have become.