I'm going to try a used better condition replacement engine I got which has a little extra power up from 3 to 3.5 hp Briggs. I needed to use a different setup as the crankshaft on the engine is not the same 5/8, now 3/4 and also is short shaft can't fit the clutch. I'm going to try using a sprocket of either 12 or 13 tooth on the 3/4 engine crankshaft. It will route to chain to an already existing jackshaft on the bike. I can have that live jack shaft either 1:1 ratio or 1.083:1 ratio as the clutch is 13 tooth.
This means I have to instead have the clutch fully engage at engine speed above 2000 rpm if I use the smaller engine sprocket 12 tooth. So it would be 2166 rpm to lock the shoes, I wonder would it be useful that way? Maybe get up and go better if the engine and clutch work. Otherwise I'll just go 1:1 ratio in the first chain.
Over all ratio will be available to switch from 19:1 ratio, 13:1 ratio and 10:1 ratio. I probably would rule out the 10:1 as a long time ago 8:1 is the way I started out, it never worked. 13:1 is a bit slow. 19:1 less torque but I have powered though viscous mud with run up speed.
Here is the old clutch I have and it looks rusty, but is cleaning up and the shoes move OK. The back idler pulley was used with the other engine and belt clutch, but it can be switch back to the old engine with belt if I decided or something happens requiring it. Anyway I've not ran with the engine and tested yet the toothed clutch, it is a brand I can't find info on. It is a Top Man clutch an says manufactured in Rancho Cordova, CA. You ever known of this brand clutch?
I don't have ground clearance for this