Plug modification

Good morning folks

I completed the coil mod for my /76 KZ900 two days ago. When I got the bike, Accel coils and Dyna S ignition were already installed. This included the use of graphite wires with no resistance cap. I put new wires on as well as the old ones were ratty. I installed new NGK BR8ES plugs but was wondering...

With the current ACCEL coil / wire configuration, should I move to B8ES plugs and forget about the plug resistance?

I'm a Mech Eng. not an Elec Eng.

I could be wrong but I believe the resistor part of the plug is just for noise and does not have any actual "resistance". Anybody?

I did measure some plugs one time to locate a low idle miss, on my Camaro and found them in the 5k to 6K range. No these were AC resistor plugs. I found seven plugs were at 5.1k, and the last one was 6.3k, so I took my meter to the store and measured new plugs until I found one close the the others.

What componuded the miss was the higher resistance plug with the longest plug wire.

And my feeble mind tells me there was a post here about this, or I dreamed it.:blink:

My thoughts were that since originally, I believe the bike stock wires were copper core, not graphite and had resistance caps. thus the resistance plugs. Since I'm running graphite wires I figure I could go to non-resistance plugs.

just trying to get the fattest spark I can

With the coil mod, Dyna S, and Accel coils, you're not going to get much hotter spark than that. But, yes, you don't need resistor plugs if you are using resistor wires. (You also don't need resistor caps.)

I dumped the BR8ES plugs in favour of B8ES plugs about a year ago when I got no resistance caps. My coils and plug wires are stock. I have no idea if the stock kawa wires are resistance wires. Anyone know ?
Anyway, I dont think I noticed any difference between the two types of plugs.
I also did the coil mod... Now that made a difference.

Its going to have to wait for me to really test the coil mod as it was snowing here yesterday. I did drag it out of storage and went around the block on Friday. Definitely its running better!

But my face shield fogged up wayyy too thick for a real good test

Thanks folks, I'm going to try the B8ES in the spring and give both a good once over....

ugh.... c'mon April!!!!!!

Here's a good article on the whys and wherefores of using resistance plugs, plug wires, and plug caps.

Note that on our vintage bikes (before 1979) many opt to go without any resistance whatever since the only reason for having it in the first place on these bikes was to reduce ignition interference with radio communications (at least that's my interpretation -- and suspect some may actually relish the idea of messing with a nearby vehicle's ear piercing boom box performance. :evil:)


www.motorcycleproject.com/motorcycle/text/plugwiretech.html

With Dyna S coils, and copper core dyna wires (caps already built in -- believed to be non-resistor type caps), and NGKB8ES plugs, the electrical current goes all the way from the coil to the plug tips with no resistance.

With NGKB8RES plugs, the R identifies it as a resistor type plug.

If decent radio reception (through an aerial or antenna) is important while riding, use of one or more of the resistor elements (wires, caps, and/or plugs) should help reduce the pick up of ignition static in the signal.

Just guessing, but suppose the later model bikes, especially those with CDI systems, would require resistor wires, plugs and caps.

Bic Darklighter wrote:

Thanks folks, I'm going to try the B8ES in the spring and give both a good once over....

ugh.... c'mon April!!!!!!

Be optimistic !

I'm thinking March !