Plug-lead & cap preference

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G'day

Could someone confirm/advise on the best set up for the ignition system for my 850 fitted with an original (black box) Boyer system. Should it be :
Wire plug leads
Non- resistor spark plugs
non-resistor plug caps

cheers

george
 
Surely you need a resistor in there somewhere, either plugs or caps (but not both)?
 
The later Boyers need a resistor, yes.
But as far as I know, the earlier analog version does not. I ran for years with the black Mk III, no resistor wire or plug.
 
Hi on my 850 with a Boyer I run non resistor wires and plugs but NGK resistor caps.
 
The easiest thing to do is run copper wires (Packard 440), non-resistor caps, and very commonly available R-type spark plugs.
Jaydee
 
If you run resistor caps then you don’t have remember, or worry about availability of, correct resistor plug
 
I just received my new Micro MK 1V Boyer Bransden Norton kit and it is paired up with copper core HT leads and NGK ceramic resistor caps rated at (5K Ohms). It states that it must use resistor plug caps of 3.50 Ohms , not less. Hope this helps.
 
I just received my new Micro MK 1V Boyer Bransden Norton kit and it is paired up with copper core HT leads and NGK ceramic resistor caps rated at (5K Ohms). It states that it must use resistor plug caps of 3.50 Ohms , not less. Hope this helps.

Does it say that?


The reference to "3.5 Ohms" refers to coil primary resistance. 5k ohms is 5,000 ohms.

http://www.boyerbransden.com/pdf/KIT00053.pdf
"The maximum ignition coil current through the unit must not exceed 5 amps. The total ignition coil resistance should not be lower than 3.5 Ohms."

Analogue ignitions such as the Micro MkIII and IV do not need resistor caps or plugs. Digital ignitions normally do.

http://www.boyerbransden.com/faq.html


"Why Do I Need To Use Suppressed Plug Caps?

MKIII and MKIV do not require suppressed plug caps for operation although we recommend using supressed 5000 ohm plug caps. Micro Digital and Micro Power units must be fitted with supressed plug caps. Plug caps fitted with suppression resistors are usually fitted to prevent radio interference. Radio interference (noise) can cause more complex electronic circuits like radios and computers to malfunction."

"What HT leads do I need to use with Boyer Bransden ignition system?

For all our motorcycle ignition systems, copper wire leads with 5000 Ohm suppressed plug cap is our preferred method, although the MK4 systems can be used without any suppression on the H.T. leads if required. When using Suppressed spark plugs, non-supressed caps are recommended. We don't recommend carbon core HT leads because the resistance of the core will vary with the length used and can increase greatly with vibration and age. Although this increasing resistance should not damage an ignition unit, the ignition coil will work at higher voltage and the spark at the plug will become progressively weaker as the core degrades. All Micro Power kits are supplied with copper core HT lead."
 
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3.5 ohm plug caps! You hope in vain.
Re-reading instructions as supplied ... yes it seems the 3.5 refers to total coil resistance. Not cap. The Micro MK 1V High Power unit states analogue. So if the 2 12 V. coils have this resistance already I take it I can fit either the non suppressed stock caps or the 2 new 5 K ohm suppressed ones. I'll start work this evening.
 
Re-reading instructions as supplied ... yes it seems the 3.5 refers to total coil resistance. Not cap. The Micro MK 1V High Power unit states analogue. So if the 2 12 V. coils have this resistance already I take it I can fit either the non suppressed stock caps or the 2 new 5 K ohm suppressed ones. I'll start work this evening.

Coil primary resistance is nothing to do with plug cap/plug resistance.

Analogue ignitions generally do not require resistor plug caps although electronic ignition manufacturers often recommend they are used.

Two 12V coils? Which model Commando is it, as '71-on have two 6V coils as standard?
The recommended coils to use with a Boyer MkIV are two 6V or one 12V dual coil.

http://www.boyerbransden.com/pdf/KIT00053.pdf
"With this system two 12 volt coils can be used [in series] as long as they are in good order. The standard 6 volt coils do short out to the metal case, check for damage by the mounting clamps. A single dual output coil can be used as long as its primary resistance is more than 3 ohms. This should be mounted on the frame in a manner that will take the heat from the centre core."

"For low compression engines two 12 volt coils (4 Ohm) in series are satisfactory, for racing and high compression engines two 6 volt coils (2 Ohm) in series, or one 12 volt 3.5ohm or more primary winding resistance dual output coil will give the best results."
 
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Yes it's a 76 MK 111 and uses 2 6 Volt coils. Been a while. I just finished pulling the very early model Trispark out to do all this change to this MK 1V Boyer kit. I know some would disagree with this decision but I don't trust it being shaken about in a hot small space anymore. Back to work on it.
 
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