Building a motorized bicycle: Question

[Gibsonvair]

My (21 yr. old) son and I are building a motorized bicycle from parts we have around. It started out with a lawn-boy converted for horizontal operation, then morphed to a 85cc Techumseh brush cutter motor. (better starter and easier to attach clutch to the crankshaft) We are using the bottom bracket of the bicycle with sealed bearings and a 3/4" key-slotted shaft for a jack shaft. We robbed a torque converter from a go-cart and are adapting the driven pulley to fit on the brush cutter motor. The problem I'm having is sourcing and adapting a sprocket for the rear wheel. Any suggestions?
Steve Gibson

 

[Gibsonvair]

progress on motorized bicycle

My son and I made some progress on the motorized bike. We fitted a jack shaft in the bottom bracket using a sealed precision bearing kit from the local bike shop, about $30.00. We test fitted a worn out sprocket from a go-cart on the rear freewheel. I hogged out the center hole with a die grinder and bolted it to the sprocket. Works! Right now I'm notching the frame a little to clear the cooling fins on the head.
Steve Gibson

 

[mike75925]

making it work, cool