Reply To: Bernard W317 no spark

[sidevalve5]

‘You pays your money and takes your choice’ with mag testing. A ‘Proper’ test rig would be one that can rotate a magneto, be able to measure the voltage and current output of both the primary and secondary coils. Ideally be able to view the sine waves on an oscilloscope and check the spark gap in air with a 3 probe adjustable tester. For flywheel magnetos, similar except without a magnet passing over the coil, a current is supplied to the primary coil.

Without access to such equipment, only static testing can be carried out by measuring the resistance of the LT and HT circuits. This is carried out with a multimeter.

Condensers can be tested either with a megger or the capacitance function of the high quality multimeter. Have found a lot of ignition problems are caused by the condenser. As I do have a megger, I can test one. For those who do not have access to one, my recommendation if the LT and HT circuits seem OK, is to replace it. But I fit a modern polyester film capacitor with a Voltage Rating of 630v. Capacitance 220nF / 0.22uF. Can get 10off for £4.09p here https://www.ebay.co.uk/itm/301127883221?var=600476142172 I mount them on a small circuit board, but you may get away with a small piece of stiff plastic.

Testing a mag with multimeter is easy, it only takes a few minutes. If I find a fault in the coil, I replace it. If I still do not get a 6mm air gap spark, I replace the condenser with the capacitor above. For me, it’s worked every time. Although I there are some mags with a suboptimal windings on the coil and/or tired magnets. As yet, I have not had one. When I do I will trial again a single wire energy transfer coil system and get the magnets remagnetized.