I like the looks of your set up better than Staton's axle mount. Your engine sits higher and looks like it would be better protected than the axle mount he has. His 5:1 gearbox maybe superior than the Pocket Bike tranny that you are using, but If you are considering ponying up and getting the axle mount. I would first look into if you could run a set of freewheeling cranks. This would make your drive ratio variable, rather than fixed.My question is: although this chaindrive set up is crude & brutishly Israeli, is there anything markably better or worthwhile available that would deliver better performance or be notably lighter, pending the availability of Staton's axledrive system?
It sucks that Staton changes his site so often that links never point to the intended target for longer than a few months.They're thread-on freewheel sprockets. An example of a shimano freewheel sprocket is shown below. They're designed to thread on 1-3/8 inch, 24 TPI hub. Staton makes several freewheel adapters, to allow you to mount a freewheel to a shaft. His adapters can be used on shaft sizes ranging from 1/2 inch through 1 inch. Available sprocket sizes for this thread-size range from 16 teeth, up through 22 teeth, and I believe I remember seeing a few 25 tooth ones. There are also similar, thread-on freewheels with a flange, so you can bolt larger sprockets up tp them.
Here's a link to his 3/4 inch adapter.
There's another, me(ric standard thread-on freewheel, which threads onto 30mm X 1mm thread spacing, which allows smaller sprocket sizes. (as few as 13 teeth)