1951 AJS 18 - Carb drama - restoration fun

[Troyumph]

Hi there! long-time reader, first time poster.
I've been slowly tidying up my 1951 model 18 and finally got to the stage of trying to give it a run the other day. I have the mag a quick once over and with a fresh plug checked the spark, it was strong and constant.
I'd pulled apart the carb and gave it a thourough clean, checking and replacing perishable washers/gaskets etc.. so it was time for a big kick
After giving the primer a tickle fuel was dripping from all over the place but I gave it a decent 50 kicks and it finally started up and got me up and down the street with many a backfire and stutter.
I only had a little bit of fuel in the tank so it ran out pretty quick but when I filled it up and tried to go again it just wouldn't start.

I'm thinking the carb might not be right or could be replaced with something more reliable?
The current Amal carb is stamped 928. Is this a suitable Amal for the job? At some point it was running well according to the previous owner (who is family and has no reason to lie)
For me, reliability is key as I'd like to take it on the track when I can.
Has anyone successfully converted to a Mikuni VM28 or something similar?

Cheers!

[JimFitz]

Hi Troy

If it has been sleeping for a long time it is usually mag problems - they can die of old age!

The spark may be ok in open air when the mag is cold but when the mag warms up and the spark has to work under compression, problems you describe start to show up. Does it start again when it has cooled down?

Jim

[Troyumph]

Hey Jim,
Cheers for the reply, it definitely got worse the warmer it got. What would you recommend for refurbishing the mag completely?

Cheers!

[JimFitz]

A re-wind and a new condenser would definitely be money well spent Troy. Mag problems are notoriously difficult to diagnose without putting it on a test rig.
If it were me I would rule out ignition problems first as you can end up going round in circles if you have carb problems too.

There are many good mag builders here in the UK but not sure about your part of the world. We do have many forum contributors from Aus who will no doubt post some suitable rebuilders.

Good luck with it and let us know how you get on.

Jim