Hitchcocks Forum

Acquired a new HT lead specific to my Enfield as a spare.When checking with multimeter I was reading total continuity ie no resistance.Should there not be a resistor fitted in the spark plug cap giving resistance for electrical noise suppression.

A copper core lead won't have a measurable resistance on its own. Typical plug cap will be 5 ohms but you can get 10 and also unsuppressed at 0. Resistor spark plugs are usually 5 ohms. If you have a magneto you would want as little resistance as possible. More modern electrics can usually cope with one or both of these. Some people only use a resistor plug OR cap but not both together. Depends on your bike and how strong your ignition system is.🔧🔧

The question of 1 or 2 resistors - one in plug and one in plug cap - gets varying answers. NGK advice - and they should know - is as follows:

All motorcycle manufacturers now comply with current legislation which demands a standard of noise suppression on every vehicle. This is achieved usually by fitting NGK resistor covers though in many cases a combination of NGK resistor covers and NGK resistor spark plugs (R type) is necessary to satisfy the ministry tests. It is emphasized that despite the use of both resistor covers and spark plugs in such engines, due to the unique and superior construction of NGK products there is no loss of performance or shortening of service life.

I would imagine that what NGK is true of modern ignition systems, though it directly contradicts what is generally held to be true about old Lucas magnetos that need all the help that they can get. (they were designed before TV sets became commonplace so interference wasn't a big issue. I note that NGK is not saying that both a resistor plug and cap should be used, merely that they can be. NGK wants to sell as much as it can...... I no longer believe they are the best make, they do seem to have a relatively high number of duff plugs if forum posts are to be believed. Just saying. In similar vein has anyone else noticed that some oil companies are now selling engine oil for vehicles with stop/start systems? One wonders why, since the stop/start invariably doesn't kick in until the engine (and hence the oil temperature) is warm enough? More sales opportunity than necessity, says this cynic.

I was passenger in a Nissan Qashqai recently that stopped at a busy traffic light junction--- engine turned off and electric handbrake deployed....Come the Green light and NOTHING !!---- No matter what my friend the driver did the car refused to start......You've seen the current advert with John Cleese and the "Incorrect starting procedure" ???........... Surprising just how difficult it is to explain to the driver behind you that it's not your fault by using hand gestures !!..........Sorry Jamesy, straying a bit "Off-thread" there but I thought it might brighten the day a little !!

Does the range on your multimeter go that low? Most of them operate in kiloohm range.



I have mentioned before, it is perfectly possible to remove the resistor in an NGK plug cap and replace it with a similarly sized piece of metal (like a stainless bolt with the head cut off).

Sure, there's not 'must' about it. And different types of ignition may require different applications. As for NGK no longer being the 'best' because they make 'duff' plugs - I don't believe it. IMHO 'duff' plugs are the result of other factors than the construction of the plug. 'Best' plugs? - I have preference for Denso Iridium [0.04mm tip compared to NGK 0.06mm tip - I know it makes 'no difference' - but I like the idea!).

When a second plug dropped its electrode into the guts of his YZ500 race engine, NGK told my friend (multiple times British NSA sprint champion and builder of his own motors) that their plugs weren't suitable for use in 2-strokes. This left him in the odd situation of being sponsored by NGK but using denso plugs.

This is my multimeter set on 0 to 200ohms.stinkwheel

So guys is it ok to use this lead on my 2003 bullet 350 with a ngk B7HS spark plug.

Since we're vaguely on the subject, anyone got any thoughts on side-gapping plugs? I'd imagine this would have some real advantages for enfields with their high combustion chamber volume and thirst for oil.