Villiers Mk 12/1 coil question

Hi all this is my first post and hope someone can help. I have a cement mixer with a villiers Mk 12/1 engine. It was not running when i bought it. I replaced head gasket, ground in the valves, done valve clearance and sorted the timing, put a new petrol tap on , cleaned carb out, and cleaned out fuel tank. Then great it was running and used it a few times for a project im doing in the garden. Then last week  it decided to die mid mix, so I shovelled out the cement and started it up again, it ran for a bit then died. Then again today (after putting in some fresh fuel) I started it up again and was fine for about half hour (done a few mixes) then it died and refused to start again.

Now im considering that I might have a problem with the coil, but if it was the coil would it run and then stop ? Im going to check the ht lead and cap tomorrow for resistance but it all looks alright.

Anyone know what the primary and secondary resistance for the coil on a Mk 12/1 coil should be, and the ht lead and cap for that matter ?????????.

Note there is no heavy oil fouling on spark plug.

Thanks

Fuel starvation can give symptoms like that too.  
If you are quick when it starts to die, try putting the choke on partly or briefly.  If it recovers, even if only briefly, that suggests it's leaning out, probably due to a blockage somewhere in the fuel supply to the float chamber.
Be interested to hear how you get on.

Cheers
Darryl

Thanks for the reply there; I have now tested the coil and there is an open circuit in the secondary. Im surprised the engine ran for as long as it did under load; at least it should run alot better with a new coil (in retrospect it was misfiring quite a bit). My issue now is getting a replacement coil, the coil for the Mk 12/1 is the batwing type and I cannot get a cheap replacement from fleabay, Villiersparts.com say they have two being rewound and no idea when thy be ready to sell, and when they do it will cost me £50 plus postage.

Is there anyone out there with a coil for a Villiers Mk 12/1 to sell, or anyone know someone who can rewind mine ?