4 stroke reliability and parts availability / build advice

[Toby woodman]

okay. would a torque converter on a lifan gx160 replacement be better with that gear ratio

 

[Toby woodman]

like this

Here's the thread on how to attach the CVT to a small engine.

49cc 4-Stroke 30 Series Torque Converter Build

Thought I would share my first build as I have seen some conflicting info about using a 30 series torque converter with a small engine like with this 49cc 4-stroke. I did not document this very well, as this was done over 2 months. The bike has run perfect and has about 300 miles on it. You...

motorbicycling.com

Normally, a builder would put a CVT on a larger engine such as a 212cc then a small sprocket (10t) to a larger sprocket on the rear wheel (44t). Meaning only 1 chain is needed on the left side. This would give them a very drive ratio drive system.

The other option would be to put a centrifugal clutch on the 212cc with a 10t sprocket then run it to a jackshaft with a large sprocket such as a 30t. There would also be a second smaller 10t sprocket on the jackshaft that ran to a larger sprocket on the rear wheel such as a 44t. Meaning 2 chains are needed on the left side. This would be a fixed ratio drive system.

By combining a CVT with a jackshaft you can then use a small engine such as a 49cc. Meaning you'll need 2 chains on the left side. However, you'll have a varying drive system. It'll be like starting out in a low gear and automatically moving to a high gear as you speed up. As you begin to slow down it'll automatically return to a low gear. Currently nobody has a build like this.

 

[Sidewinder Jerry]

I know there's a Honda GX 160, if you have specs on the engine you're talking about it'd help

 

[Toby woodman]

I have found a 3/4 inch shaft 4 stroke engine with 6.5 hp. if I set it up like this with a torque converter a 10 tooth sprocket like you said a builder would normally use and a 44 tooth sprocket. surely it would be too fast? as shown above

 

[Sidewinder Jerry]

I have found a 3/4 inch shaft 4 stroke engine with 6.5 hp. if I set it up like this with a torque converter a 10 tooth sprocket like you said a builder would normally use and a 44 tooth sprocket. surely it would be too fast? as shown above

The Lifan GX 160 is a clone of the Honda GX 120. It's a 118cc size engine. It has 4 hp at 3600 rpm. With the Lifan 160 you could hit 30 mph by running a reduction as low as 9.28\1. You'd still have to use a jackshaft even with a CVT.

The point I'm trying to help you see is you can run a high revving smaller cc 4 stroke engine and still get the same results. Bicycle frames can deal much better with the smaller cc 4 stroke engines than they can with the large ones.

 

[Toby woodman]

why would I need to run a jackshaft. with an 8 tooth cvt sprocket and a 60 tooth wheel sprocket surely that would be fine

 

[Chainlube]

why would I need to run a jackshaft. with an 8 tooth cvt sprocket and a 60 tooth wheel sprocket surely that would be fine

You need a jack shaft only to offset the chain drive to rear wheels because the CVT and engine are wider that a typical 2t mount.

Ideally you'd want a 10 or 12 tooth on your CVT to a 60 tooth on your wheel.

 

[Sidewinder Jerry]

why would I need to run a jackshaft. with an 8 tooth cvt sprocket and a 60 tooth wheel sprocket surely that would be fine

Here's some of the problems you're going to encounter. I'm almost certain the smallest sprocket that'll fit on a 30 series torque converter is a 10t. However, if I'm wrong and you could get an 8t to fit on it a 415 chain wouldn't function very well with a drive sprocket that small; a 60t sprocket is huge to be putting on a rear wheel. The CVT range is 3~1\1; meaning you'll have a total reduction range of 22.5~7.5\1. Yes, 6.5 hp could power a 7.5\1 reduction for a speed of 37 mph on level ground using 26" tires. To have 6.5 hp you're going to be using a very large cc 4 stroke engine. You're going to be very limited as to what bicycle frames you can use and will probably have to do a lot of welding to modify it.

 

[Sidewinder Jerry]

My personal choice of engines would be either the Honda GX 50 or the Huasheng 144. Use a 30 series CVT with a 10t to a jackshaft (40t,10t) to a rear 44t. You'll have several bicycle frames to choose from; with minimal modifications. You'll have a bike that's legal in most places where self built motorized bicycles are allowed, can go up any hill and do 30 mph on level ground using 26" tires.

 

[Toby woodman]

could you send a picture of a jackshaft that would work. also I'm unsure how to attach a cvt to a hashing 144