Frame mounted belt driven Honda


New Member
Local time
7:24 PM
May 15, 2008
So I think I've finally determined enough to be able to start posting info about the motorized bicycle I'll be making. I saw that oscully and Sheik Yerbouti have been working on the belt driven frame mount for awhile, but haven't heard whether they have made any real progress since March. Also I found that Sianelle had started to work on a design using a vintage engine, but changed it to make a helper wheel. Since no conclusive proof seems to exist yet, I will be stepping into somewhat uncharted waters half blind.

The Donor Bike:

A 7 speed Schwinn Jaguar (that I bought at Target) that's been modified with a vintage all metal Shimano derailler (none of that plastic ****), a springer front fork, chrome ducktail fenders, black leather touring seat, white wall road tires, a chrome luggage rack, and a chainguard off a 1941 Columbia Superb (I'll post photos when I get it all assembled). For brakes I'll be using a v-brake in the back and a side-pull brake in the front (until I can find a Sturmey Archer front drum brake in stock somewhere).

The Motor Bits:

The motor will be a frame mounted Honda GXH50 4 stroke engine with a v belt centrifugal pulley clutch. From the clutch I plan to use a short 1/2" v belt to a 5/8" (shaft) x 6" (dia.) pulley that shares a shaft with a 5/8" (shaft) x 1 3/4" (dia.) pulley that in turn drives a 20" BMX bicycle rim (it's actually 15 1/2" in diameter for whatever reason) that's attached to the rear rim of the bike via 6 or 8 (haven't decided yet) steel brackets like the old 1903-1912(?) Harley Davidsons and the old Shaw Motorbikes (Here's a 1910 Shaw for reference). The total setup will give an approx. 18:1 gear down of the Honda motor (which from previous posts seems like the best gearing for these motors). The pseudo-jackshaft will be mounted to a plate with a pivot point at one end that will have a small heavy duty spring attached to it (to keep tension on the belts and allow them to be changed). I then plan to mount an old Briggs and Stratton cylindrical gas tank behind the seat on the front of the luggage rack.

The Custom Panniers
I found a supplier of dark brown oilskin (the stuff Australian dusters are made of that's 100% waterproof) that I plan to make my own improved version of the Brooks Brick Lane Roll-up Panniers out of. It'll cost less than the Brooks version, be 100% waterproof, have better closing straps (buckles instead of the magnets that they use), look better, and have a vintage flair. Also if I'm happy with how they turn out, I might start making and selling them to interested motorized bicyclists and regular bicyclists at a nominal fee (ain't shameless self-promotion grand).

The problems I haven't figured out yet:

1. Where to find the 5/8" shaft with bearings to attach the reduction pulleys and how to mount it to the pivot plate.
2. I'm pretty sure the same place that sells the pulleys also has the belts I'll need but I don't know how long they'll need to be yet.
3. Motor mount. I haven't figured out if ThatsDax or Bicycle-Engines sell just the motor mount out of their kit or not. I know I can get the wide crank, muffler, and throttle linkage I'll need from them without buying a whole kit, but I'm not sure about the mount yet.

I'm sure there are other problems I'm neglecting, but that should be a good start. I'll try to get photos of the donor bike up later this week if I get a chance.

Peace and Chicken Grease does sell the grubee adjustable mounting plate seperately. They are pretty proud of it though as they charge $50.00 for it. But short of a custom mount I don't think there is any better.

5/8 Jackshaft and bearings should be available from most of the Go-Kart Supply/Parts stores. You also might find spending some time on the Max-Torque web site benifical . Look at how he sets up the jackshaft on his Torque converter and he has some really good links to Go-Kart Suppliers.

As for my Belt Drive Set-up I've just this week recieved tha various pulleys, drivers, clutch and jackshaft parts and will be posting photos over on the GiantStone thread by the weekend.