Have a John Deere L118 with a Briggs and Stratton engine. Starter turns but won't engage engine, sort of like an old car with a flat spot on the flywheel. Is there an adjustment on these starters? It's three years old with about 115 hours on it.

More than likely, you will find that the nylon bendix gear on the top side of the starter is stripped out. You can purchase the gear kit for a lot less than a new starter.

Thanks for the response. I just took it apart and the nylon gear is intact and spins when the starter is engaged but doesn't move the 3/4" or so it needs to engage the flywheel. Do they just freeze up over time? I can't even seem to get it to move with a screwdriver or anything.

Well it is bad then probably. They usually will move even when they begin to wear out. The gear not moving without a screwdriver prying on it sounds as though the inside of the gear is worn. Carry to the shop and let them look at it.