Powerdynamo, what sparkplugs and caps to use for PD systems

Powerdynamo brings new ignition & light
to your vintage motorcycle



Technical Help



We often get asked what spark plugs and spark plug caps (with or without resistor) should be used with our systems

The answer regarding spark plugs has 3 parts:

a) use the plugs suggested by the manufacturer of your motorcycle or comparable ones should the stock versions no longer exist.
     Also use the electrode gap recommended by the stock manufacturer. On singles, you may try to set this gap a little wider to max. 0.6mm. 
     On twins or tripples you should better use 0.4mm. Some Kawasaki tripples give 0.6 as standard. Please do not use 0.6 but reduce to 0.4
b) use new plugs from known manufacturers (see our Information on bad plugs )
in our instructions you will find the statement: "You will be doing yourself a favour to treat your bike to new spark plugs and spark plug caps (preferably some with a resistance of between 1 and 2, maximal 5 Kilo-ohm).  Such caps are e.g. available from Beru (BER WOA/14) or NGK (NGK XD01F-S). Plenty of problems are to be traced back to apparently good (sometimes even completely new) sparks plugs, terminals and cables." 
c) Do not use spark plugs with an intern suppression resistor. (coded with an "R" for resistor, such as BR or WR) together with resistor caps. This doubles resistance and may lead - notably with our twin coil arrangement - to problems in starting.  How to check total resistance of the HT circuit see here.

We have from several customers reports that (the expensive) multi earth plugs (be it triples or quadruples) solve many a non explicable problem experienced on our ignition systems.
We can not explain why, but it is indicated again and again to us.

There are 2 factors contradicting each other in some ways, but have to be taken into account both of them.
You will have to comply with your national radio anti-interference provisions and you have to find a means to get ignition started with the sometimes pitifully low starting revolutions of classic, or even vintage motorcycles.

When using am resistor cap, make sure it does not have resistance above  5KOhm (when hot this often rises significantly). In metal shielded caps the resistor is often lower as the metal also suppresses. So better use them. When you use HT leads with rubber plugs without resistor (for dirtbikes), such as we supply with certain systems, you  have to use spark plugs with inbuilt resistor (save perhaps for use outside public roads).

our offer for such resistor caps see part 70 10 500 00
back to KB overview