Just my opinion. I bought a Schwinn Aerostar MTB with full suspension and mounted a GEBE kit with the R/S 035 4-stroke engine. Works perfect. The tires are real agressive nobbies and a bit wide - were touching the belt. A couple of washers on the engine side of the drive gear and away I went. Its an all aluminum frame and built real strong. I have a picture of it on the post "Two engines one bike" Don't let the title scare you as I have not done it yet! Lot of good bikes out there. Stay away from disc brakes if you can and talk to Vaughn at GEBE. They are all good people there and will help you with any problems. Ask them about their exaust extension.