M21 drive sprocket options

[berniej]

I've just rebuilt an M21 (1957 rigid) and used the sprockets and chain wheels that were with it as previously built.

I suspect it may have been geared for sidecar use and I plan to use it like that again at some point.

However, for running in I'm using it solo and today was the maiden voyage after a few decades of rusting in an Irish bog.

The bike ran very well but feels like the gearing is too low for solo use as the revs are well up at around 40-45 m.p.h.

I guess that the simplest option for changing would be to fit larger engine and/or gearbox sprockets and keep clutch (6 springer) and rear chain wheel the same?

What would be the recommended combinations be please? (I'll need to pull the primary cover to count what I currently have and will update the post later with the numbers.)

Thanks,
Bernie

[Dean Southall]

Engine sprockets
Solo 20T
Sidecar 16T

[berniej]

Thanks Dean, I'll pull the primary cover and see what I've got in there.

Cheers,
Bernie

[Pete C]

unless you are going to be lugging something like this, fully loaded, I probably wouldn't go for a 16 tooth sprocket. 

[berniej]

Wow, is that a sidecar or a small caravan!? 

Mine's actually a small single seater Briggs so pretty light.

I may be OK with what I have but the clutch started slipping on the maiden journey with sidecar so I had to abandon after about 10 yards.
Removed the sidecar to fix the clutch and then decided it would be kinder to run in the newly built engine without the additional load.

So, it seems a bit low geared for solo use but might well be right as it is with the sidecar back on. I realised I hadn't counted any of the sprocket teeth so might as well do that before it goes back on.

Cheers,
Bernie