homemade jackshaft 80cc raw engine 8speed hub

hi all

im in the end stages of a motorized bike build.
i used a 1960's murray beachcrusier frame (the engine front mount fits!) an 80 cc "raw" engine.
i made a rear engine mount (see pic.) and a bearing mounting plate for the jackshaft.,,,

jackshaft: engine side 30 tooth sproket.
pedal side 16 tooth freewheel
rear wheel drive cog 10 tooth

rear hub: sturmey archer 8 speed with drum brake with 25 tooth cog
front hub: sturmey archer with drum brake


it is the best motorized bike i have ever had (my third)

Nice looking. That's a good solid jackshaft mount.
Is it up and running yet?

its up and running,.. tested lights tonight,. installed speedo 24.5 mph in third gear at 3/4 throttle (dirt road,. still shake testing the thing,..)ill go faster once motor is broken in a little more and i can take longer rides,.. so far a very enjoyable ride.

Sounding good. Nothing like having gears on these things. (Got a Sick bike Parts shift-kit into 6-speed derailleurs on mine.)

What kind of freewheel are you using on the pedal cog?

Where did you get the parts?

where did i get all this stuff?

pedal side of the jackshaft is a standard 16 tooth freewheel on a freewheel adapter from staton inc (5/8 shaft 3/16 keyway)
rear wheel chain drive cog 10 tooth for 410 chain also from staton on 5/8 shaft w 3/16 key

engine side 30 tooth sproket and freewheel sproket adapter (sick bike parts) on a 3/4"shaft freewheel adapter (staton inc)

shaft ,.. made by myself on friends lathe and mill 3/4 inch on one end and 5/8ths on other end (if i were to start over it would be a 5/8ths shaft)

bearings: standard 3/4" flange bearings modified some to make them less wide ( again, made by myself on friends milling machine and surface grinder at work)

bearing mount plate: 3/16th plate steel from local steel
supply 1" slot milled up center (friend again)

rear motor mount: section of mountain bike handelbar(i think) vendor : scrap bike pile outside shed.

chain tensioner,.. made from a piece of 1"x 1/8" bar stock,
derailler wheel from pile o' parts, made on a drill press and a small (micro) milling machine(unimat!) with 2 screen door springs for tension.

this is not a project for anyone whom does not know thier way around a machine shop (im a machinist).

pbeggs said:

this is not a project for anyone whom does not know thier way around a machine shop (im a machinist).

Click to expand...

You said it.
For the rest of us, with only a drill, file and hacksaw, the Sick Bike Parts shift-kit works well.