I was hoping that some of the experts might help me with a magneto problem. I pulled my B34 out after the winter and could not get it started. Checked it over and found no spark. I tested the HT wire and spark plug and both are fine. I did notice a very small spark between the contact breaker points. The bike worked just fine when put away for the winter.
I'm obviously no Lucas magneto expert! Does anyone have any hints.
Assume you have all ready removed plug cap from HT lead and tried to see if there is a spark directly from the HT lead.follow this logic down to the pick up brush. Also the points can sometimes get a corrosion film on them that acts as an insulator -First try cleaning the points. Also see if there is any evidence of up and down play at the points end. if so your petaled insulating washers around the mag bearings are goners and must be replaced. I doubt if it is the condenser in the armature as they usually only decide to quit when hot.
Thanks for the reply Rob. I cleaned the points and set the gap. I notice that I am getting intermittent spark that will jump about a half inch to ground. I removed the pickup, cleaned it and then cleaned the slip ring inside the magneto. I tested the continuity through the pickup and it seems okay. When I kick it I get a pretty strong spark, but then no spark for the next several kicks, then one spark again. Any ideas? I'm stumped.
sounds like you may have to take the mag off and disassemble. First check for up and down play as i said previosly. I have seen quite a few mags recently where the petaled fibre insulating washers are allowing the armature to go to ground
What type of HT lead are you using ? This is exactly how graphite ( silicone) car leads behave. It is essential that you use either a solid copper conductor or even better are the spiral wound leads any thing else will give you grief often intermittantly and drive you crazy
No spark with new "clean" plugs or no spark with old plugs ? Modern "fuel" will quickly coat the electrodes and is quite conductive at cylinder pressure. Pull one out , hold it upside down and "cook" the thread with a strong flame ( oxy ). If there is a deposit there it will start to burn off and yield a quite yellow ( rich) flame.
The fact that you're getting a strong, but intermittent spark makes me think that perhaps your points may not be 100% cleaned up. Could be that you still have a spot of oxide remaining, which will prevent the points from making a good closed contact every once in a while.
I would remove the points and scrape them clean, ensuring there are no pits or oxide remaining. Then, for good measure, coat with a preservative like Electrolube.
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Thanks to all for all the tips. I changed the points to my spares set, which are brand new and surgically clean and replaced the plug - but the problem persists.
I obtained a spare mag that was recently rebuilt from a friend, but the manual advance/retard control cable threads are stripped. Does anyone know if I can take a spare left-hand end cap(complete with cam face, etc.) and swap it for the stripped right-hand end cap?
I'll use the spare mag until I can get the original refurbished.