Spark plug cap resistance

[Audioslave784]

How much resistance should there be in the spark plug caps? I'm getting about 500K ohms in two of mine, and that's after cleaning the pieces pictured below. Shouldn't this resistance be close to zero?

And is that little metal bar supposed to be conductive? I'm getting zero conductivity through that, even after I cleaned the surface.

Thanks.

 

[chuck hahn]

those are resistors rated at 5,000 OHNS. they were put in there so that your AM radios in the fairings wouldnt hum from spark plug noise like the old cars did. You can either eliminate them and replace them with a piece of 1/8 inch brass rod cut to that length, get new ones from radio shack or an oldies car parts catatlog or replace all the cap ends with regular ends and buy resisitor plugs. dealers dont sell the resisitors sepearately..I tried. Gotta buy a complete boot, so its just easiest to do the brass rod gig.

 

[chuck hahn]

I bet you mysteriosly lost spark and thought a coil went bad....didnt you!!!! The screw in brass thing is what slips on and grips the spark plug no resistance in that...just the rersistor should have the 5,000 resistance.

 

[rustybronco]

As Chuck said, 5,000 ohms. I was going to take a trip down to Radio Shack and see if I could get some 5K- ?? watt resistors to fit in place of them, but I just can't seem to remember every time I go by.

My thought is to coil the axial leads and use them in place of the stock resistors. then they should work in a pinch.

 

[chuck hahn]

I got the brass rod like Ed suggested and it is in all my bikes and yes radio shack can order them for around 2 bucks each..so i am told.

 

[resjudicata]

Chuck or anyone else who has replaced the cap resistors with brass rod, are there any downside/problems with doing this?

I found over the weekend that my caps had over 35k resistance and replaced the resistors with copper. Now, I'm trying to decide if I really want to buy new caps or just leave them as is.

Thanks,
Chris

 

[rustybronco]

Chuck or anyone else who has replaced the cap resistors with brass rod, are there any downside/problems with doing this?

I found over the weekend that my caps had over 35k resistance and replaced the resistors with copper. Now, I'm trying to decide if I really want to buy new caps or just leave them as is.

Thanks,
Chris

With your '79 I see no issues. if you are still worried, either order new plug caps, or continue to use the brass rod substitute and use BR8ES spark plugs.

http://thegsresources.com/_forum/showthread.php?p=1244133#post1244133

 

[Flyboy]

Ok, so let us assume that one is not going to be running a radio or anything of that nature that can be subject to ignition interference on the bike, could one then buy new unsuppressed caps and just run normal B8ES plugs, and do away with the suppresion altogether?
Maybe to get cleaner, more reliable spark.

 

[rustybronco]

Yes you could do away with the resistor(s) (suppressors) altogether given your stated terms.

(I wouldn't try that on a bike with 'electronics')

 

[Flyboy]

(I wouldn't try that on a bike with 'electronics')

Granted, well seeing that the most electronicaly advanced component on my G is probably going to be my cell phone in my pocket, I am good.

I always tell the passengers on the DC3, feel free to use your cell phones in flight, this aircraft is 100% fly by wire technology................ 3/8 inch stainless steel wire to the control surfaces. :lol:

 

[rustybronco]

Granted, well seeing that the most electronicaly advanced component on my G is probably going to be my cell phone in my pocket, I am good.

Does your "G" have electronic ignition or points?

 

[Flyboy]

Does your "G" have electronic ignition or points?

Mmmmmmmmm, electronic, good call, never thought about that, could it really mess with the electronic ignition?

 

[rustybronco]

could it really mess with the electronic ignition?

Yes.......

 

[koolaid_kid]

Wouldn't another alternative be to replace the wires with resistor wires? I found that AutoZone sells individual resistor wires for $5 each. This would give you new caps AND new wires. If you do this, you have to put the screw-on caps back on the plugs since automobile spark plug wires normally use them.
Just a thought.

 

[resjudicata]

I have a Dyna S ignition on my '79 now. I went for a ride with the resistors removed and didn't see any issue. I could see how the field for electronic pickups might be interfered with.

I have some new NGK caps on order. They are cheap and they will look better than the old ones I have now.

Chris

 

[Flyboy]

Ya, I don't have an issue with it, if the resistor needs to stay, then so be it, I was just thinking that by doing away with it that it would ensure a fatter, stronger, cleaner spark.
One reads so much about issues on these old systems, with weak spark, hard starting, poor running etc, and all the mods and bypasses that can and should be done to overcome the problems, to me it just seems logical to start at the root and ensure clean path of flow for the current, do away with anything that is not really required for the healthy running of the engine, before adding in all kinds of whizz bang gizmos to compensate for a flawed system.
As was stated, the resistors were merely installed to suppress ignition noise on radio equipment.
But if the removal of them will bring on ignition module problems, then it stays.