125-200cc Muffler core glowing red hot after top end running??? whats going on???

Hi there
I have a sms125 here with FMF gold pipe and power core 2 exhaust

i was pushing the bike to its max top end tonight after went to ace-cafe in london and found my exhaust firing out red ashes and thanks for driver behind warning me as well

so when i stopped i found my muffler core is red hot and managed to cool it down by idle the bike for a min to let air through it

can anyone tell me whats actually happened??? and thats the first time i saw my bike do that in a while so im bit worried

thanks

Lean a/f

Lean sounds right, probably the main jet. What's the jetting?. Random thought, do you happen to have header wrapped? That moves heat from the header to the can. I can't imagine just being lean alone would make the core glow.

EDIT: Oh, Duh! It's a 2-stroke. nvmd.

What oil are you running ? Sounds like you had a spooge / Coke buildup in the pipe and your high speed run set the carbon to burning inside your pipe causing it to flake off and blow out the end of the pipe. Similar to how you clean out a carboned up 2 stroke pipe with a blow torch.