Success!! Fitted a Nova II module and now have sweet running Villiers Mk25.
The only issue I found with the Nova module is that the spark is generated 180 degrees from the original contact breaker. The Mk25 flywheel contains two magnets, one small, one large. The original contact breaker setup had the points opening as the smaller magnet reached the 12 o’clock position. After fitting the Nova module, I set the flywheel in the same position it had been in, which produced a puff of smoke from the carburettor every time I tried to start it. This could only happen if the intake valve was open, so I knew the timing was way out. As the ignition module is triggered by a magnet passing the coil, I guessed that the module was using the larger of the two magnets, so rotated the flywheel 180 degrees. This now produced kickback when trying to start, but at least I knew the spark wasn’t far from where it needed to be. After a couple more attempts, rotating the flywheel a few degrees at a time, I found the sweet spot.
The actual fitting of the module was very simple. There is a stud on the outside face of the armature plate which can be used to connect an engine stop wire. I connected the positive terminal of the module to this stud, as it is wired back to the coil. The negative was connected to one of the mounting studs for the fan cowling. As I had removed the whole contact breaker assembly, is used one of the now redundant mounting holes for bolting the module to the outside of the armature plate. I could have mounted the module directly in place of the contact breaker box, but was worried that it might not have enough ventilation, as they do get hot in use.
Thanks for your input chaps.
Sean
