And now for something completely different!!

[cloakedvillain]

The rim diameter on 20" wheels is around 16 inches, could definitely use moped rim ans tires if you wanted.

You can build up a custom wheelset: You'll want double walled aluminum rims. Steel will never run true. It will wobble at the spot welded seam.

You have to make a decision on the axle. There are hollow axles (QR and thru axle) or solid threaded axles. I recommend a freehub (cassettes not freewheels) no matter which style you choose.

8 speed altus rear derailleurs work very well and are very cheap. You can find these, new in box on ebay for 12-16 usd with free shipping. pair that with an 11-34 cassette, and a narrow wide chainring, and you will have decent shifting.

Some discussion on that ktm 50 engine here: Thread 'Next 2 stroke build idea.' https://motoredbikes.com/threads/next-2-stroke-build-idea.65139/

I think the internal reduction is 3.5:1 but I could have counted wrong.

 

[Pezz]

Still contemplating this build. . .

Some could rightly say going around in circles . . . . .

I wanted to build it rather light and would prefer 4T even though the KTM50 is a great option.

Also considering an internal gearbox's as apposed to the derailleurs a bit like Allen Millyard made about 20 years ago.


View: https://www.youtube.com/watch?v=S39oR_7Vwf8

 

[Gordy]

Maybe a CVT might fit this particular build a bit better. Gear boxes can get very expensive. Unfortunately light and four stroke don't tend to mix unless it's severely under powered.

Unless maybe you went with a honda ohv 50cc engine. Still under powered, but perhaps enough gears could get past that? I've seen people use the gear box from a motorcycle engine by running a cain to the crankshaft of the motorcycle engine, but that makes for alot of complexity and alot of vibration

 

[Pezz]

Maybe a CVT might fit this particular build a bit better. Gear boxes can get very expensive. Unfortunately light and four stroke don't tend to mix unless it's severely under powered.

Unless maybe you went with a honda ohv 50cc engine. Still under powered, but perhaps enough gears could get past that? I've seen people use the gear box from a motorcycle engine by running a cain to the crankshaft of the motorcycle engine, but that makes for alot of complexity and alot of vibration

Thanks for your input Gordy, I appreciate it

Agree with the low power engine means gears, lots of gears

Also considering the 79cc HF motor. Are they dimensionally smaller than the 212 for example?

Once I settle on the motor, I can look at the appropriate 'gearbox' options.

I had thought of a small capacity 2T gearbox with the cases cut off as they have self-contained oil supply.

As I want it light weight, I'm leaning towards deraillieur gears as I can get more ratios

 

[Gordy]

Thanks for your input Gordy, I appreciate it

Agree with the low power engine means gears, lots of gears

Also considering the 79cc HF motor. Are they dimensionally smaller than the 212 for example?

Once I settle on the motor, I can look at the appropriate 'gearbox' options.

I had thought of a small capacity 2T gearbox with the cases cut off as they have self-contained oil supply.

As I want it light weight, I'm leaning towards deraillieur gears as I can get more ratios

The 79cc from harbor freight is considerably smaller than the 212, but difficult to get more power out of.

 

[cloakedvillain]

The 79cc dimensions according to the retail website:

And the 212 dimensions:

A lifan 125cc pitbike engine would get you 4 speeds, about 8 hp and weight about 50lbs. Build using one: https://motorbicycling.com/threads/latest-lunacy-honda-ct70-clone-build.36108/

Here's a thread using a 2hp utility engine and a 3 speed hub: https://motorbicycling.com/threads/strange-brew.60263/

 

[Pezz]

Forgot about Motorbicycling and Im on there too

Just reading them now

I had thought of a sturney archer hub as an option.