If the engine will not start, or runs very poorly, try this.

[Tornadoman]

I see questions about starting all the time. Here is a mystery that had me baffled. The B&S engine on our rider was not starting. It had fuel, spark, compression. Everything an engine is supposed to have to run. I was dumbfounded. I removed the cover from the top just to have a look. As I was closely examining it I noticed the cutouts for the flywheel key and crankshaft did not line up. So I pulled the flywheel off, and surprise! The flywheel key had sheared. New key, and the trusty old B&S is still running ten years later.