classic motorcycle forum

We are assuming there is nothing untoward going on here,
like a case full of broken teeth jamming up the works. !
Without a full inspection, its a bit of a lottery if this will be good.

Draining the oil and inspecting what comes out is a useful diagnostic tool.
If its nice and clean (and new) it can go back in ?

Can you turn the box over at this point, using the back wheel.

The leading 2 teeth on that quadrant are not ground down at all.
This gives a rather brutal initial engagement, and they can jam.
Ground down a bit, they lead into the others, and swing into action. !

If that were mine, I'd get out the angle grinder with a thin blade,
and shave a bit off the 1st 2 teeth.  Keep the same basic tooth shape,
just shaved a bit, and no sharp edges left.  Easy does it....

So can you now kickstart it OK ?

Is that a fast click click, or slow
The chain contacting something could be a slow click,
but a fast one needs further investigation.
Even the tyre contacting something

Don't recall, is this bike new to you.
Some fettling is to be expected....

P.S That box is later than the CP expected for 1951 ?

Thank you for your kind advice my BSA is now running better than it ever has. Advancing the magneto timing a little has ensured that it’s now in the sweet spot.

Hi R yes tried rocking in gear still no joy