Any Briggs and Stratton one or two cylinder would fit. I put a two cylinder 20 hp. Briggs and Stratton out of a John Deere L111 barn find on my L100 which previously had a 1 cylinder 17 hp. Briggs and Stratton. You must use the exhaust pipes and muffler from the donor tractor. I did the transplant for a winter project and I now have 200 hours on the twin cylinder transplant. I still have the original engine as a backup. There are a lot of good used engines out there due to tractors with failed transaxles and rotted mower decks. The farmer I got the L111 from said it had been sitting in the barn for 8 years because the mower deck was bad an not worth fixing. He gave it to me. If you buy a new two cylinder engine they are expensive and you will also have to buy the exhaust pipes, muffler, gaskets and choke lever with a cable.

 

My son has rebuilt the top end of both engines and they continue to fail. He has done it on both engines twice. I figured everything else works on the lawn tractor. I read that someone replaced their engine but then the hood was hitting the muffler. Do you know what model number may work or a popular size that fits a basic JD riding mower.

 

Any Briggs and Stratton engines that fit on a 100 series (big box type) John Deere will fit your tractors. The frames are predrilled to accept the different bolt patterns on the one cylinder and two cylinder engines. A one cylinder would pretty much be a direct fit, since you already have a one cylinder. A two cylinder would require you to obtain the correct exhaust pipes and muffler to fit properly without hitting things. I once bought an old John Deere L100 for $50.00 because I wanted the transaxle for a spare. It ran great but the mower deck was rotted away, the body was rusted, seat torn and the hood was missing. I gave the engine away.