riding lawnmower muffler help?

Question

We have a mtd yardmachine riding lawnmower.Trying to mow grass yesterday and about 10mins later the muffler got cherry red and was very hot.What could be the cause of this?And also right after start up you could see some smoke coming from it.Please help if you can.

Answer 1

You need to change the spark plug. Your mower is probably misfiring and your gas is burning in the muffler. The spark plug may have been fouled by a host of things including dirty fuel. My wife did this once by putting gas I had mixed for my two stroke engine into the four stroke lawnmower.

Answer 2

Mufflers do get hot but that is a bit extreme. I would look for an air leak between the carburator and the engine. An air leak would cause the engine to run lean and hotter. Also the ignition timing could cause the engine to run hot. About the only way to change the timing is to shear the flywheel key.
There may be an obstruction in the muffler slowing the exhaust flow but that is likely to reduce performance.

I guess after the above thoughts, I would check the exhaust valve clearance. If the exhaust valve is too tight or burned it would allow combustion gases out of the cylinder and into the muffler. I would suspect a valve issue.