Murphyspug, thanks for the explanation of what probably happened in detail.
Yes I too had a muffler that I was using after it being stored for quite a while.
The last time it was run with that muffler it probably had a bit of carbon build up left in it.
I had started the engine and was running it. I saw the muffler glow red and didnít really think too much to be worried, because eventually within a few minutes it was back to normal and had not happened since.
I have a new muffler anyway, for the State requires the OHV to have spark arrestor type mufflers and my bike no longer has pedals it is for off roading when it is completed.
Later I took a video of it while messing with the throttle and while it was dropping from high rpm to idle the video captures a blue pointed flame out the muffler with a backfire!
I guess the spark arrestor muffler stops the flame from getting out the back for good reason. I have not tried it yet as I am just finishing other parts of the build and hope to have it running and with an OHV Sticker before New Years.