Spark Plug Wire Woes

I met up with @Mike T and we headed over to a Two Wheel Tuesday event. We were itching to get on the bikes after being saturated with motorcycles at Barber.

We made it about half way and my bike lost... half its power. I pulled over and then, because the street was a little busy, limped it to a side street.

I checked fuel first as it was stumbling. Good there. Poked around a bit and noticed the left spark plug wire was loose at the coil. Seems simple? For some reason it did not want to go into the coil. After some coaxing and cursing and tweaking it finally went in and stayed.

Kicked a few times and nothing. Pulled the spark plugs. Dry.

Kicked some more.

Noticed that the right spark plug wire was sort of loose on the spark plug. It was just sitting on the spark plug and not gripping like the other side. Still it should at least spark.

Finally noticed that I had apparently knocked the jumper wire between the coils off (TriSpark). Reattached that and fired up.

So what to do about the spark plug wires? Replace them? They could be original. Tweak them so they stay on better?

Otherwise, when it's running it just hauls. I credit my brother for an awesome engine rebuild and Jim Comstock for the head work.

And yes, the kids were drooling on the old bikes.

If you are going to ride the bike, replace the spark plug wires and display the originals on the wall of your garage

Why don't you just make set yourself? It's hard to do.

Yep +1
I buy the parts (incl cotton braid) from Green Spark Plug Co.
Cheers

robs ss said:

Yep +1
I buy the parts (incl cotton braid) from Green Spark Plug Co.
Cheers

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Watch that cloth wrapped HT lead...when my 850 sat in a light rain, the cloth got wet enough it allowed spark to run along outside of wire to earth. So no firing of the plug. This was with GreenSparkPlug cloth wrapped (not cotton. I believe it to be synthetic like nylon) and using their brass crimp on end fittings, which crimp down against a section of inner copper wire bent over the insulator end and included the outer cloth wrapping. Maybe next time I will try to trim cloth back so it is not crimped under the brass, or use the screw in type fittings instead.

Just need to ensure the cloth goes nowhere near the copper

Let’s face it- wrapping HT leads in something that soaks water up is a bad idea.

They may have had to do it in the 1930s, to protect rubber insulation from sunlight and atmosphere.

Let;s face it - riding an unstable two-wheeled contraption with no external protection is a bad idea,

They may have had to do that is the past due to the high cost of cars but now - oh, wait a minute...

Building a set of wires is not that difficult a job, trying to source the proper coil boot seems to be a problem. I can only find either straight or 90* boots. The factory wires has a different angle boot to clear the valve covers.

Although it's common to see the HT leads/wires routed outwards and then back to the plug caps the factory never did it that way. The leads always ran backwards over the head and then curved forwards to the plug caps.

I can't think why anyone would want to fit braided HT lead to a Commando as it's not original.

@swooshdave we in the UK cant see your Imgur pictures "Content not viewable in your region".

L.A.B. said:

Although it's common to see the HT leads/wires routed outwards and then back to the plug caps the factory never did it that way. The leads always ran backwards over the head and then curved forwards to the plug caps.

https://www.classicbike.biz/Norton/Brochures/1970/72NortonBrochure.pdf

I can't think why anyone would want to fit braided HT lead to a Commando as it's not original.

@swooshdave we in the UK cant see your Imgur pictures "Content not viewable in your region".

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I agree, but with out the slightly angled coil caps (which I was not able to locate) my choice was either straight, which rubbed on the valve cover, or 90* . I didn't have any original coil caps to reuse.

I've never found the straight type to cause any problems if the coils are positioned correctly.

They seem to want a stupid amount for delivery as they don't seem to be in the UK or I'd have bought some.

L.A.B. said:

I've never found the straight type to cause any problems if the coils are positioned correctly.

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Trust me Les, I tried every angle. That 8mm wire and heavy rubber boots I have would rub. Not necessarily when the engine was not running, but after a while I would see some chaffing. For some reason you seem have a lot more space than me. Could be the PVL coils I'm using. I would rather route them the other way because after getting caught in some bad rain storms I found water getting into the plug caps/wire joint.

With resistor spark plugs and TriSpark ignition you don't need those fragile NGK hard plastic caps unless you are showing your bike at the concourse at Pebble Beach.

I made up the spark plug wires I'm currently using with MSD 8.5mm Super Conductor wire with MSD plug caps and use Denso iridium resistor plugs. I also use the same spec coil Matt at cNw uses. (Insert the starts first kick nonsense here.)

Swoosh don't you have a spare set of nice spark plug wires laying around from your Mustang project? Just cut the lengths you need off at the coil ends and make up a new coil end connectors. It's fiddly working with the small connectors and crimpers, but the hot rod wire sets are much better than OEM Norton.

Some time back I bought new HT plug wires from A/N $$$. I Was dismayed that the coil end had straight boots, unlike original.
This has caused me routing and installation difficulties regardless of how I positioned the coil or routed the wire. Les, I appreciate
the sources for the offset boots. I will be ordering a pair.

L.A.B. said:

Although it's common to see the HT leads/wires routed outwards and then back to the plug caps the factory never did it that way. The leads always ran backwards over the head and then curved forwards to the plug caps.

https://www.classicbike.biz/Norton/Brochures/1970/72NortonBrochure.pdf

I can't think why anyone would want to fit braided HT lead to a Commando as it's not original.

@swooshdave we in the UK cant see your Imgur pictures "Content not viewable in your region".

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I suspect you are not allowed to see Imgur in the UK because it contains "offensive memes". I will leave it at that.

bmepkid said:

Why don't you just make set yourself? It's hard to do.

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If it's hard to do then why would I try?

Just kidding. I've made up countless sets of spark plug wires. Two wittle ones for the Norton isn't a challenge.

Schwany said:

With resistor spark plugs and TriSpark ignition you don't need those fragile NGK hard plastic caps unless you are showing your bike at the concourse at Pebble Beach.

I made up the spark plug wires I'm currently using with MSD 8.5mm Super Conductor wire with MSD plug caps and use Denso iridium resistor plugs. I also use the same spec coil Matt at cNw uses. (Insert the starts first kick nonsense here.)

Swoosh don't you have a spare set of nice spark plug wires laying around from your Mustang project? Just cut the lengths you need off at the coil ends and make up a new coil end connectors. It's fiddly working with the small connectors and crimpers, but the hot rod wire sets are much better than OEM Norton.

Click to expand...

Recommendations for spark plugs and wire types that might play nice with the TriSpark? I'm currently using BP7ES.

Schwany said:

With resistor spark plugs and TriSpark ignition you don't need those fragile NGK hard plastic caps unless you are showing your bike at the concourse at Pebble Beach.

I made up the spark plug wires I'm currently using with MSD 8.5mm Super Conductor wire with MSD plug caps and use Denso iridium resistor plugs. I also use the same spec coil Matt at cNw uses. (Insert the starts first kick nonsense here.)

Swoosh don't you have a spare set of nice spark plug wires laying around from your Mustang project? Just cut the lengths you need off at the coil ends and make up a new coil end connectors. It's fiddly working with the small connectors and crimpers, but the hot rod wire sets are much better than OEM Norton.

Click to expand...

I did replace the wires on the Mustang and used custom lengths. That takes a wee bit longer than on a Norton. I don't know if I have any left overs. Hopefully not.