My first build used a 2hp briggs, mounted over the rear tire and incorporated a simple friction drive. Not happy with the friction drive i tried building a couple kit bikes. they worked a bit more reliable, but still not good enough for me.
Currently i am building a bike built for two using the good old briggs, this time i will use a belt/chain drive combo, and only 1 of the two riders will be able to peddle. I'd post a pic but when i try it tells me my pic is too large and i can't seem to edit it.