I am not that impressed with the go-cart style live axle, where things are secured with a keyway and one or two set screws.
It is a quick and dirty method, but when I went to tighten the brake drum, I could not access the set screws, so at the moment I don't have any brakes (LOL, hold the safety comments please).

I have considered installing the brake drum on the jackshaft, but I suspect the stopping force will be a multiple of the sprocket ratio, ie: if the rear axle to jackshaft sprocket ratio is 2:1, then the stopping force doubles ?
I don't really want to catapult myself over the handlebars.

The good thing about a scooter is that it is a relatively small and compact machine.
The downside is that there is not much extra room on the rear axle.

I am please with yesterday's test, and the steering geometry (after I adjusted the angle of the steering shaft).
I am not too happy with the noise that is generated by the drive train.
The rear wheel needs to be trued so it runs round.

The motor is lugging a bit more than I want, at the operational speed I anticipate generally using.
In anticipation of this problem, I previously purchased a larger left side jackshaft sprocket, and I think I will add that to put me in a better rpm range while cruising.

I have a belt and pulleys I think I could add between the jackshaft and rear axle.
That would probably resolve 1/2 the noise.
If things are still too noisy, I will install a pulley on the engine, and left side jackshaft, and use an operable idler pulley as a clutch mechanism.

I would like a drivetrain that is quiet, and does not need much adjustment over time.
I am not keen on having to oil the chain(s), and the oil tends to sling off.
I am resisting the temptation of pulling a gearbox off of one of my old small Honda motorcycles, mainly because I don't have enough room to mount it, and I don't need the speed range.

I understand why many scooter and gocart builders on ytube use pillow block bearings.
They are very simple, and perfect alignment is assured.
I have a few pillow block bearings, but I think they are for a 1" shaft; I may modify them for use with the jackshaft.

1st operational test phase is complete, and is roughly what I expected.
We now move into the refinement stage.
I have about one more week to debug the scooter, and if things are not worked out by that point, then it goes on the back burner.
Looking at the scooter, there are a number of improvements that could be made, but the immediate need is that I need a reliable scooter in a week, regardless of how crude the design may be.

.

I'm running of nuts 'n' bolts on this engine, hopefully Santa will restock shortly

Slidebar cheesehead screws now changed, bearing caps tidied up and I'll take a look at the cylinder head bolts, I have trouble rounding the ends, but I guess in the lathe with a file maybe .......

Right .......I'm off to London to the Pantomime with the family.............. oh no you're not ..........

I agree with Minh, he is on the right track.
 
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Looks good and runs nicely.
If I may also give a couple of 'notes', the slide bars could do also do with hex head screws, and the studs round the cylinder could be neater.
Studs look best with the lengths equalised, at a projection above the nut of about one thread or a little more.
The one at bottom right on the valve chest cover is about right. The ends would be slightly domed.

There we go ....... studs and nuts, looks a lot better; not sure what they were actually meant to be, but but 6BA fitted perfectly!