AJS & Matchless Owners Club

I have a Triumph 21. The early alternator bikes have no voltage control and rely on switching alternator coils according to load via the head light switch. If you haven't already, I suggest you fit an electronic regulator (try Rex's Speed shop http://www.rexs-speedshop.com/), means the battery is always properly charged and I think your modern sealed battery may not take well to the lack of a regulator. Even if this is not your problem I would recommend the regulator as a modification.

I had much the same problem as this a long time ago with a Norton Commando, but one one cylinder. After much engine checking and swapping of electrical components it turned out to be the ignition coil on that side. It seemed to fail when it warmed up.

Malc

could it be that the battery is connected the wrong way round? It will give you the same symptoms
should be positive earth.
Tony

Hi,

I had a similar problem with my AJS 18. It would easily start and tickover smoothly but then as the engine warmed up the tickover would get erratic then the engine would stop and wouldn't restart until cooled down again.

The problem turned out to be insufficient tappet clearance. In one of my various AJS/Matchless manuals it states you should check the tappet clearance with the engine warm. Neither hot nor cold.

The crankcase and head is made of aluminium, barrel from grey cast iron and the valve gear from steel and aluminium. All these metals have different coefficients of thermal expansion. Thus as the engine's temperature increases all these metals expand with different components increasing by different amounts and the tappet clearances change. Therefore very carefully getting tappets right at cold can result in negative clearance, i.e. valves failing to close, as the engine gets warmer.

David.

Hi, if it's not condenser, valve clearences etc. you might check for a leak on the inlet. My brother had the same symptoms , albeit on a Greeves with Villiers engine, turned out the inlet manifold was broken in two! Don't know if it would give the same thing with a four stroke but maybe worth checking, won't cost anything to do!
Good luck, Dave.