Anybody have a transmission for sale?

[5-7HEAVEN]

Is it hard to design my own jackshaft? Like the ones that come with those monster 80 kits?

It's easy and better than what you'd get in any kit.
JMO, building an mb is like being in a high school robotics class. Jackshafts are just a piece of the machine. If you choose wrong parts, your machine fails horribly.

Your first objective is to choose how fast you want to go. Then, with 7th grade math, you can compute which sprockets you'll need.
I can help.

 

[Yellow Perch]

It's easy and better than what you'd get in any kit.
JMO, building an mb is like being in a high school robotics class. Jackshafts are just a piece of the machine. If you choose wrong parts, your machine fails horribly.

Your first objective is to choose how fast you want to go. Then, with 7th grade math, you can compute which sprockets you'll need.
I can help.

So starting out with the plate, how do I even begin to make something for the bearings to ride in.

 

[5-7HEAVEN]

Don't buy anything yet!

The build begins in your head, and on pencil and paper and cardboard.
Firstly, determine if you want low end power or speed, and at governed or ungoverned rpm.
If governed and low speed, that"s one gear ratio. If governed and high speed, that's another ratio. If ungoverned and low speed, that's another ratio. If ungoverned and high speed, that's another gearing.
You need your engine specs thru research, to determine where its torqu and hp are maximized.

You also have to decide if you're using Torq Convertor, if you decide to use the left-side sprocket. That deternines how high your ratio can be.

Choose if you're chaining the jackshaft to the left wheel sprocket, or connecting via shift kit to a multi-gear hub on the bike chain side.
Mock up your engine, using angle iron, plywood, duct tape, nylon straps, whatever. Using CAD(cardboard aided devices), place a cardboard image of your engine into the midframe. Determine if you'll use your pedals and adjust how high your engine sits.
If you choose to send engine power thru the bicycle gears, your jackshaft can be run under the motor mount.
If you decide to run engine power to the left side, you'll be installing the Torq Convertor and/or the jackshaft to the right of the power take off(PTO) shaft.
Decide exactly where your engine will sit, and everything else I had questions for you.

 

[Yellow Perch]

Don't buy anything yet!

The build begins in your head, and on pencil and paper and cardboard.
Firstly, determine if you want low end power or speed, and at governed or ungoverned rpm.
If governed and low speed, that"s one gear ratio. If governed and high speed, that's another ratio. If ungoverned and low speed, that's another ratio. If ungoverned and high speed, that's another gearing.
You need your engine specs thru research, to determine where its torqu and hp are maximized.

You also have to decide if you're using Torq Convertor, if you decide to use the left-side sprocket. That deternines how high your ratio can be.

Choose if you're chaining the jackshaft to the left wheel sprocket, or connecting via shift kit to a multi-gear hub on the bike chain side.
Mock up your engine, using angle iron, plywood, duct tape, nylon straps, whatever. Using CAD(cardboard aided devices), place a cardboard image of your engine into the midframe. Determine if you'll use your pedals and adjust how high your engine sits.
If you choose to send engine power thru the bicycle gears, your jackshaft can be run under the motor mount.
If you decide to run engine power to the left side, you'll be installing the Torq Convertor and/or the jackshaft to the right of the power take off(PTO) shaft.
Decide exactly where your engine will sit, and everything else I had questions for you.

I’d love to do a jackshaft but I’m positive the torque from the engine would destroy the bike gears. A single speed seems the most reliable. I *may* be getting a Honda gx120 or 160 from a friends power washer so the bike may have more power than I thought

 

[5-7HEAVEN]

Im guessing you mean "shift kit", not jackshaft.
Im building my 212cc to feed my bike's 7 speeds. I think with gentle application of power, and pedalling from a stop, the bike should live.
If she destroys the drivetrain, I'll remove everything and install a #41 chain and 18t on the cassette.
That'd give me a strong 7:1 gearing.

 

[5-7HEAVEN]

Yes, Honda 120/160 is good.
Single speed works well.