Hitchcocks Forum

I remember saying to my son, 'electricity isn't an exact science'. 'Yes it is', he said. 'No, it's witchcraft', I replied.

My bike is a Lightning 535 and I'm having trouble starting it from cold. Previously, I was having trouble starting it hot as well, until I noticed that it wouldn't start when the ammeter showed no negative deflection at any time (this had confused me because I thought it wouldn't deflect with the Boyer). Anyway, that seems to have been a problem with the kill switch.

When it wouldn't start this morning, I remembered that it had previously started immediately after 1) replacing the spark plug, 2) after remaking the HT lead connection to the plug cap. So I pulled the plug cap off the plug and replaced it and it started immediately. See? Witchcraft.

It has Micro Digital Boyer ignition, a suppressed plug and what I think is a suppressed plug cap (5.24 on a 20,000 ohms scale), the original Indian one. Could this be my problem? I have ordered a non-suppressed NGK plug cap, which is cheaper than replacing the two new plugs I've just bought.

You should be able to check the plug manufacturer's or a plug supplier's web site and check their lists to see if it has a resistor or not. Generally, it's either resistor plug and non-suppressed cap or a non-resistor plug and suppressor cap. NGK plugs are helpfully designated with an R for resistor plugs, eg BR7ES as opposed to B7ES.



Resistor plugs and suppressor plug caps are not recommended for older magneto ignitions, but the Boyer MD will probably need one or the other.



A.

Thanks Adrian, the plug is definitely the resistor type (BR8ES). I now know the plug cap is as well. I hadn't fully understood the multimeter reading but a bit more research has sorted that. I've done a search on here and elsewhere, and the general opinion seems to be that having two resistors weakens the spark. I'm hoping that that's where the problem lies.

Ask your son.....

Some electrical components are fussy about interference from the HT side, and the manufacturers insist you fit a supressor plug cap, check your Boyer instructions to see whether this is the case. I understand the resistor spark plug instead of the suppressor plug cap will serve the same function, but I will give way to superior electrical knowledge. Is your Boyer ignition designed to work with a standard ingition coil or does it use something different?



A.

It's a standard ignition coil. In their FAQ Boyer say, 'Micro Digital and Micro Power units must be fitted with suppressed plug caps.' Further down the page they say, 'When using Suppressed spark plugs, non-suppressed caps are recommended.' Being a bit pedantic I've emailed them for clarification.

You either need a suppressor cap OR a suppressor type plug. Pedantically that is one with an "R" in the plug number. If both have a suppressor (or resistor - same thing) the spark won't be as strong as it should be. FWIW with a magneto there should be neither a suppressor cap nor a resistor type plug. The spark needs all the help it can get.

Thanks Rattlebattle, that's what I thought. The non-resistor spark plug cap is on its way.