Ajs 16m sr1 mag no spark

[Bertholt71]

Hi, new user, recently acquired a 1959 ajs 16m. Started pretty much first time,every time. One day it started up, warmed up and then wouldn't restart. Checked the plug, only an intermittent spark. Ordered a new plug, this time nothing at all. Fitted new condenser, nothing, and then replaced the points and still no spark. I'm really at a loss and have no idea where to go next. I've even considered a thorospark conversion. I'm really stuck.

[clive]

Quick thoughts. My SR1 died suddenly a while back admittedly after a high speed chase (well high speed for a G80 two up). The problem seemed to be the condenser but a new replacement was no help. Eventually worked out the the fibre washer that sits under the points arm to keep it isolated from the rest, had worn away and fallen off. Some memory of something seeming to fall out when i took the cover off at the roadside, but could not spot anything. Anyway new fibre washer and sparks returned. Good luck.

[Rob Harknett]

correct Clive. also, if you are assembling for the first time, you must get this washer in the correct place, ( fading memory I think also correct way up) SR1 is correct for 54/G80 onwards 500cc 55 onwards 350

[Groily]

The Workshop Instructions may help if you don't have them handy, with checking for correct assembly from the exploded views. Also, for some tests you can do. http://www.brightsparkmagnetos.com/libr ... %20SR4.pdf

Always a very good idea to put a meter, resistance scale, from the plug cap to the magneto body to check for continuity.
You should typically see somewhere around 5500/6000 ohms if the plug lead and plug cap are properly attached and the HT coil isn't suffering from a break.
If there's no reading, then check the HT lead is making good contact through the magneto cover to the take-off from the HT coil, and check the resistance from the coil's HT take-off to the mag body from there. (The HT lead / cap should show close to zero ohms end to end.) If there is an infinite reading or Open Line across the coil, then the coil is the problem.

Also check on the side of the magneto, where there's a screw and nut etc, that it has an undamaged insulator where it goes through the mag casing, and if there is a bit of tin to press to stop the engine, or a wire off to a remote kill button, check that isn't making permanent contact to earth. That screw is 'live' and is usually where the condenser live lead and the low tension live wire from the HT coil are secured, with a wire off to the live point down below. If the condenser was replaced, check too that the metal connector isn't touching anything it shouldn't. Anything to earth there will kill the thing stone dead.

This more general review of the SR may also be useful
http://www.brightsparkmagnetos.com/libr ... gnetos.pdf

Hope is it's 'only' something minor like the washer mentioned already - but the coil is the risk element and the high cost bit.

Oh, addendum - if the mag has the metal end cover, make 100% sure it can't touch the connectors where the low tension wire(s) go to the contact breaker at about 6 o'clock. It's a common issue with the metal jobs.

[Bertholt71]

Thanks for your replies, I'll have to examine further. This is the first 'old' British bike that I've owned and so magnetos are a very new thing to me. Once again, thanks.