Norton 19S - No spark?

Assuming that the spark comes from a magneto here are the easy things you should check/replace, not necessarily in this order: 1 Does the magneto turn when you kick over the engine? 2 Do the points open and close as the magneto turns? 3 Are the points correctly gapped (0.012")? 4 Are the points clean? 5 Is the spark plug correctly gapped (0.022") 6 Is the spark plug clean? 7 Swap the spark plug 8 Swap the spark plug cap (must be non-suppressor type for a magneto) 9 Swap the HT lead (copper cored).

If you still don't have a spark at this stage you are probably looking at a faulty magneto. It could just be one of the 2 brushes (Earth & HT slip ring) but more likely a failed capacitor or winding insulation. Consult one of the magneto specialists.

Hope this helps, Ian McD

I doubt that you have caused any serious harm. Work through the checklist above, that may reveal a simple problem that will restore the spark. If you can get a spark then check the ignition timing (on a 19S, full advance, the points should open at 11/16" before top dead centre). If the timing is wrong it could explain the bangs. If you still can't get a spark then I'm afraid you will need the services of a magneto specialist. One other thing, some modern spark plugs have resistors built in. Do not use this type of plug with a magneto.

If it did start then timing can't have been totally wrong at that time. If it went "bang" and now refuses, it is possible that timing has slipped due to sudden shock.

But starting cold and not starting hot are classical signs of magneto issues.

Previously Ian MacDougall wrote:

I doubt that you have caused any serious harm. Work through the checklist above, that may reveal a simple problem that will restore the spark. If you can get a spark then check the ignition timing (on a 19S, full advance, the points should open at 11/16" before top dead centre). If the timing is wrong it could explain the bangs. If you still can't get a spark then I'm afraid you will need the services of a magneto specialist. One other thing, some modern spark plugs have resistors built in. Do not use this type of plug with a magneto.

Just out of interest, why not use this type of plug with a magneto? I understand there is no benefit but what is the drawback?

The resistance decreases the gap the spark will jump on the plug.

http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20magnetos%20generally/Are%20suppressors%20and%20resistor%20sparking%20plugs%20OK%20to%20use%20with%20magnetos.htm

As you can see, a suppressor does appear to require the magneto to do considerably more to achieve a significantly poorer spark. Also, note that the higher the voltages that the HT winding generates, the greater the risk of breakdown of the insulation of the HT winding.

That's encouraging. Next step is to see whether you still have a spark when things get hot (as suggested by David). If there are no other urgent issues to deal with take it for a run, 10-20 miles should be enough but have a back-up plan to get home again if the sparks give up!

Cheers, Ian McD

Previously john_holmes wrote:

The resistance decreases the gap the spark will jump on the plug.

http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20magnetos%20generally/Are%20suppressors%20and%20resistor%20sparking%20plugs%20OK%20to%20use%20with%20magnetos.htm

As you can see, a suppressor does appear to require the magneto to do considerably more to achieve a significantly poorer spark. Also, note that the higher the voltages that the HT winding generates, the greater the risk of breakdown of the insulation of the HT winding.

That makes sense. Thanks!