Vintage Horticultural and Garden Machinery Club

Hi Dave,

When undoing the flywheel nut, there is a few turns when the nut feels free, where it transitions between tightening onto the crankshaft and starting to pull the flywheel off the taper. It then goes tight again and if you continue to turn or hit the spanner, it almost has the feel of a thread stripping. But it is just the action of the flywheel pulling off the taper. If the nut turns free for several turns but the flywheel is still firmly on the crankshaft. Then you will have stripped a thread and would hope its not on the crankshaft.

Have read with interest your ideas about fitting and external coil and battery. About 14 years ago I purchased a Clifford Mk1 that was in great condition, except there was no spark. The vendor was very up front about it and said he thought the coil was duff. He said it may be possible to fit an external single wire energy transfer coil, similar to a Honda C50. He was right about the failed coil, so did some research and decided to have a go. The system was developed by trials riders in the 1960’s, whose Villiers engines had reliability problems. They stripped the secondary windings off the ignition coils, linked the primary with the lighting coil and fitted a 6v external coil. Without a lighting coil, I just stripped the secondary windings and attached the single wire to the external coil to the hot side of the points. No spark, so gave up on the idea and got a replacement from Villiersparts. It was not an exact copy and needed a bit of work to fit. But the results were a good fat spark.

I now know why my attempt of fitting an external coil did not work. The voltage generated by the primary winding was not enough to induce a spark. It is why the 1960’s conversion used two coil windings. In an ideal world the ratio of primary to secondary windings should be 1:10. The method I should have done was to strip the coil completely and rewind the primary using 22swg enamelled wire, putting 350-400 turns on the soft iron core. Still have the external coil, it was I recall only £12 and have vouched that the next time I have a duff coil. I am going to have another go at fitting it. The advantage being that the voltage generated by the primary will create stronger lines of magnetic force within the secondary. At the moment of flux reversal and when the points open, the magnetic field rapidly collapses. The voltage produced will be greater, therefore a bigger spark at the plug.

However, all of the above may be superfluous to you. Once you get the flywheel off, you may just clean and adjust the points and job done. I like to obtain a spark at 6mm air gap and use a cheap adjustable spark tester for this. 4mm is OK, it will run, but starting and tickover is better with the greater gap. If no or weak spark, then get a multimeter and test resistance. HT continuity should be 3000 – 7000 ohms and LT 0.5 – 0.7 ohms. If you are inside these ranges but still no or a weak spark, then in all likelihood the coil is OK, but the condenser if duff. This can be tested, but will need a megger to check the insulation resistance is 200M ohms. Its probably better to replace it and I would fit a modern capacitor. I fitted one from Brightsparks with fantastic results, all of the above test figures and methodology I obtained from them too. They have a brilliant website that goes into magneto ignition in great detail. Note that Villiersparts sell a modern condenser, but do not know its specification. Subsequently I have got some polyester film 630v 220nF/0.22uF capacitors and fitted those. Again with brilliant results.

Best of luck with everything.

Grahame