Engine is running lean.
Well there is no possible way because the 2006 Suzuki SM-400 can be hot wired.
Could be that the muffler is clogged, it is running extremely lean, or there is unspent fuel burning in the exhaust pipe. This is not completely uncommon and may not be a sign for alarm.
It is normal for the exhaust to get hot. It is the result of an internal combustion engine. If the exhaust is red hot then there is a problem, perhaps from excess fuel or incorrect timing.
exhaust?
Yes, it happens when the catalytic coverter is clogged
Advanced timing can cause that to happen
I dirt track race and mine did it once it was because it was running to lean.
The exhaust gasses pass though there, and they're really hot.
it is burning way too rich.
Hot adjustment on the 1.3 engine is .009-.011 clearance on the Intakes, and .010-.012 clearance on the Exhaust valves
No but an engine running like that can damage the valves.
Engines run by burning gas fumes- fire is hot- exhaust is therefore hot. Hot gases running through metal pipes will make the metal hot. Hence the reason for "Hot, do not touch" stickers on many small engine exhausts.