Spark Plug Wire Woes

[swooshdave]

Sorry.

This isn't life or death. It's just spark plugs.

 

[Tornado]

Better to not double. IMHO, Bad to use resistor wire on a motorcycle, too much vibration for carbon-core wire. I use copper wire and resistor plugs.

The total resistance from coil to plug is what matters...a short bit of ht supressor ht cable should not add much...less than 1k? Just avoid using a 5k ohm cap with a 5k ohm plug.

 

[swooshdave]

The total resistance from coil to plug is what matters...a short bit of ht supressor ht cable should not add much...less than 1k? Just avoid using a 5k ohm cap with a 5k ohm plug.

So just measure the resistance in the wire and see where it is? What's the max resistance for the entire chain that would be acceptable?

Some searching show maybe a max of 10k ohms. NGK Resistor plugs are specced at 5k. I'm checking with DynaTek as to what their wires are at per foot (or meter). That should give me a total estimate.

 

[robs ss]

I assumed it was because I have resistor wires. Isn't it bad to double resist?

I use resistor plugs, copper wire and resistor caps. Trispark - no problem!
Total resistance measured at about 10k
Cheers

 

[Schwany]

So just measure the resistance in the wire and see where it is? What's the max resistance for the entire chain that would be acceptable?

Some searching show maybe a max of 10k ohms. NGK Resistor plugs are specced at 5k. I'm checking with DynaTek as to what their wires are at per foot (or meter). That should give me a total estimate.

I've got two never used and never will be used by me NGK BP7ES plugs and some V-Power NGK non-resistor racing plugs in the 7 heat range. If you were closer you could stop by and get them for your experiments. I'd be surprised if they worked without an occasional misfire with cheap plug wires, but who knows.

 

[swooshdave]

I've got two never used and never will be used by me NGK BP7ES plugs and some V-Power NGK non-resistor racing plugs in the 7 heat range. If you were closer you could stop by and get them for your experiments. I'd be surprised if they worked without an occasional misfire with cheap plug wires, but who knows.

Who said I was using cheap wires?

 

[marshg246]

Who said I was using cheap wires?

No one should - resistor wires cost more and are much harder to make!

 

[ashman]

Well I got my stock of N7YC plugs and 3 tune up kits from Joe Hunt with cooper core plug leads so I am right for about 20+ years, still can't work out why non resister plugs are being phased out by the plug manufactures, don't they know there are still old cars and MCs around.

 

[Tornado]

So just measure the resistance in the wire and see where it is? What's the max resistance for the entire chain that would be acceptable?

Some searching show maybe a max of 10k ohms. NGK Resistor plugs are specced at 5k. I'm checking with DynaTek as to what their wires are at per foot (or meter). That should give me a total estimate.

Yes, just check with your Ohmmeter how much resistance from coil end of HT lead to the plug boot contact, add in the spark plug resistance...that's your total. Suppressor HT wire typically states (sometime printed on the outer coating) how many Ohm's per foot of length....its not much. Max allowed depends on the EI you have...most spec no more than 5k Ohm total (ie TriSpark, Wassel, Boyer)...but the small added resistance from the short run of suppressor cable will not hurt things.

 

[Tornado]

I use resistor plugs, copper wire and resistor caps. Trispark - no problem!
Total resistance measured at about 10k
Cheers

While it will work, Trispark and other common EI's call specifically for no more than 5k Ohm....unsure if this is due to the electric circuitry with the EI hitting heat limits or something to do with the coil limits.

 

[Schwany]

Who said I was using cheap wires?

I guess I did. Oopsie

The Dynatec copper core wires cost more than the graphite silicon core wires contrary to advice here. Only $6 more than what you bought though. Currently copper core is $29.99 down from $33.99 on the Dynatec site. The graphite core stuff is $23.99.

I know you made a decision not to buy copper core. But you could have had copper wound under graphite with a kevlar core and 8.5mm silicon EMI suppressor plug wire. Which works extremely well with EI and resistor plugs regardless of what others imply without ever using such wires. It is possible that is what the 7mm DynaTec wires are, but their description of the products and specs is not that great.

You don't need anything special except you actually do need the right combination of parts. It doesn't have to be anything I would use or suggest. I don't belong here, and I figure I will be ignored for the most part. I'm just trying to correct some potentially inaccurate information about suppressor spark plug wire.

Excuse my handing out information nobody wants to hear. It's a gift.

 

[marshg246]

Let's not go overboard on what Tri-Spark says on the resistance subject. They say:

We recommend the use of spark plug suppressor caps (5k Ohm caps such as
NGK LB05EP) or resistor type spark plugs - not both together. An ‘R’ in the
spark plug part number denotes resistor type.

The 2nd word is key. Although I use resistor plugs, Tri-Spark works fine without them with good wiring. But if you use devices for GPS or other things on your bike, you may have problems. The resistance is there to reduce electrical noise, not for sending rockets to Mars!

BTW, take your ohmmeter, hold the leads apart .025" with your meter on the highest scale - still reads infinity? The addition of fuel/air and pressure certainly changes that resistance, and once the ionization of the fuel/air happens and a spark is formed, the effective resistance is much lower but WAY more than 5k ohms. Even 50-year-old Lucas 6v coils can produce MUCH more voltage than is required to make a spark with resistance in the circuit. However, a much higher compression engine at very high RPMs might overwhelm old Lucas coils ability to produce a spark.

 

[swooshdave]

DynaTek doesn't publish the specs but they responded very rapidly to an email. Their 8mm wire is 3k per foot. So if I were to use resistor plugs (NGK for example at 5k) that puts me not quite where @robs ss is. But it looks like the non-resistor Champions are readily available.

 

[Tornado]

DynaTek doesn't publish the specs but they responded very rapidly to an email. Their 8mm wire is 3k per foot. So if I were to use resistor plugs (NGK for example at 5k) that puts me not quite where @robs ss is. But it looks like the non-resistor Champions are readily available.

Unsure how you can use much more the 5 or 6 inches on a Commando HT lead?

 

[swooshdave]

Unsure how you can use much more the 5 or 6 inches on a Commando HT lead?

There are two typical routes for the wires. One uses an angled plug at the coil and drops the wire right onto the spark plug. The other way is to use a straight plug at the coil, go backwards and curl back to the plug. Both are acceptable and one is longer than the other.

 

[mdt-son]

Maybe the engine vibration causes internal ruptures in spark plug wires? There was a comment in another thread about plug wires which tested to correct resistance, yet refused to transmit the required voltage to fire the spark plugs.
This sounds strange, but high voltage behaves different to low voltage. If the insulation has cracks and oil has crept into the insulation, the mantle itself may become a conductor of HV current too, at much higher resistance than the copper core, causing intermittent firing.

There is a tool for testing plug wires and caps which I didn't know about.

Motorcycle Not Getting Spark? (Reasons and Solutions) - Bike Restart

Damaged spark plug wire; Worn-out spark plug; Weak battery; Blown fuse; Kill switch issues; Damaged safety switches; Ignition coil problems

bikerestart.com

It looks like a very usable tool.

- Knut

 

[Triton Thrasher]

Am using scrap 240 volt PVC clad mains flex as plug leads at the moment.

I moved the ignition coil back behind the oil tank to get it away from engine heat, so needed very long leads.

 

[robs ss]

There is a tool for testing plug wires and caps which I didn't know about.

Motorcycle Not Getting Spark? (Reasons and Solutions) - Bike Restart

Damaged spark plug wire; Worn-out spark plug; Weak battery; Blown fuse; Kill switch issues; Damaged safety switches; Ignition coil problems

bikerestart.com

It looks like a very usable tool.

- Knut

I carry one of those at all times. It tests for spark under actual compression and reduces risk of damage to Trispark:

Post in thread 'Condenser question'

Jul 7, 2022

To see if the condensers have anything to do with your problem, remove them. Their primary job is to prevent sparking at the points. A little running without them won't hurt. If they fail open, the engine will run fine but the points won't last. If they fail closed there will be no spark. If they fail partly closed the spark will be diminished.

I disagree - they act as filters, removing the AC current through the points, AC current gives a much weaker spark, with that characteristic yellow/orange colour. Will spark in open atmosphere but not under compression.
I am somewhat...

• robs ss

• 

Cheers

 

[marshg246]

I carry one of those at all times. It tests for spark under actual compression and reduces risk of damage to Trispark:

Post in thread 'Condenser question'

Jul 7, 2022

To see if the condensers have anything to do with your problem, remove them. Their primary job is to prevent sparking at the points. A little running without them won't hurt. If they fail open, the engine will run fine but the points won't last. If they fail closed there will be no spark. If they fail partly closed the spark will be diminished.

I disagree - they act as filters, removing the AC current through the points, AC current gives a much weaker spark, with that characteristic yellow/orange colour. Will spark in open atmosphere but not under compression.
I am somewhat...

• robs ss

• 

Cheers

Not going to argue this again. It's a simple quick test and even if you were right, which you are not, the test is still valid.

I don't understand why you tied that old post into a post about an inline spark tester which I also use. There are no condensers when Tri-Spark is installed.

 

[robs ss]

Not going to argue this again. It's a simple quick test and even if you were right, which you are not, the test is still valid.

I don't understand why you tied that old post into a post about an inline spark tester which I also use. There are no condensers when Tri-Spark is installed.

If you open the link I talk about and post a link to that tester - that's why