I just got a MTD garden tractor/mower. It hasn't been used for several years, so it needed a new gas line, and some tires replaced. But the
12.5 HP Briggs engine fired right up.This engine is missing a muffler. It just has a piece of pipe sticking out about 4". Although the engine runs well, there are blue flames coming out of that pipe, which shoot out as far almost a foot. I'd guess that explains why the muffler is gone.
But what puzzles me, is that several times per minute it sounds like a gun is fired, (explosive sound) and an extra big yellowish flame shoots out. This does not affect the engine speed, and it keeps running well. But it is unusual. What could cause this? It almost seems like a valve is leaking, but I'd think that would also cause the engine to run poorly.
One thing I have noted is that after I have run this mower for about an hour, these explosions have become much few per minute, but they still occur.