resister spark caps

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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resister spark caps

Postby rump » Thu Oct 19, 2017 4:25 am

Do you need resister spark plug caps when using electronic ignition if so why. rump from australia.

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Re: resister spark caps

Postby Rob Harknett » Thu Oct 19, 2017 10:53 am

Resistors are used to prevent interference to radio, TV signals etc. Ark welders will also cause interference. Perhaps the resistor helps prevent this interference of the plug sparking, which it will do regardless of it having, mag, coil or electronic ignition. I am sure a person of electrical knowledge will now come along and confirm or correct that .

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Re: resister spark caps

Postby g5wqian » Thu Oct 19, 2017 12:01 pm

you dont need any resistor plugs or caps with anything for it to run properly .
they are simply for suppression of interference to radio and tv .
they came about when cars were fitted with radios .

dont use any resistor plugs or caps with magneto ignition , you will lose so much spark it might not even spark .

some use resistor leads made of carbon .

it is best to use copper cored plug leads and non resistor plugs , and if you have electronic ignition and want to suppress it because it causes interference then use resistor caps .

most of the older british bikes used non resistor everything and i think the suppression products only came in during the late 60s and 70s .

most tv and radio is now digital and so those who are watching or listening to it are not going to detect interference as would have been seen years ago .
at the most the screen or sound will simply freeze , and that happens often enough with a weak signal and without any interference caused .

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Re: resister spark caps

Postby thornebt » Thu Oct 19, 2017 1:34 pm

It's not just radio and TV signals that are affected by non-resistive plugs. They can also interfere with various systems fitted on more modern vehicles including engine management systems, ABS and even air bags! Cheers. Bruce.

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Re: resister spark caps

Postby Expat » Thu Oct 19, 2017 1:40 pm

Garmin gps units too!!??
Keep shiny side up.

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Re: resister spark caps

Postby rump » Sun Oct 22, 2017 2:43 am

In the 40,s we used shirt buttons wired between plug lead and spark plugs this stopped plugs oiling up what is the theory behind that. That gap in the button holes where the spark jumped seemed to make the spark stronger. rump aust.

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Re: resister spark caps

Postby rump » Sun Oct 22, 2017 2:44 am

In the 40,s we used shirt buttons wired between plug lead and spark plugs this stopped plugs oiling up what is the theory behind that. That gap in the button holes where the spark jumped seemed to make the spark stronger. rump aust.

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Re: resister spark caps

Postby Rob Harknett » Sun Oct 22, 2017 7:30 am

Perhaps the button acted a bit like a capacitor, stored the current up a bit until spark built up in strength to jump the gap in button holes.

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Re: resister spark caps

Postby Groily » Sun Oct 22, 2017 8:47 am

Have a read of this if you can bear it rump. A long-ago serious discussion of the 'series gap' issue: http://naca.central.cranfield.ac.uk/rep ... ort-57.pdf
You'll see that the merits are dubious; although there are many 2CV Citroën owners who say it gets them going on damp days!

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Re: resister spark caps

Postby aobp11 » Sun Oct 22, 2017 10:00 am

Here is an illustration I once made for the Dutch AJS/M magazine. Albert.
button.jpg
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