Greetings. Five years ago I purchased a Staton-Inc friction drive unit with a Subaru Robin 33.5 cc engine and mounted it on a recumbent bike. I put 100 miles or less on the engine then removed it from the bike. A few weeks ago I came across the engine in the garage and after checking the oil and filling it with fresh gasoline it fired up on the first pull. I'm now interested in mounting the engine on a 2004 Trek 7200 Hybrid bike but I want to switch to a chain driven configuration. The gear and chain drive unit for the Subaru Robin 33.5 cc engine is priced at $399 on the Staton-Inc website. Is there a less expensive alternative for a gear and chain drive unit that will work with my Subaru Robin 33.5 cc engine? Any input is appreciated. Thanks.