Interspan Ignition

Cobra Classics

Cobra Classics

Joined
Jan 31, 2023
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Hi all,
Currently restoring a 1970 Norton Commando engined race bike for a client. The ignition that came with the bike is a twin lead Interspan unit. My query is that most of the bike came dismantled so I'm not sure how the Interspan unit wires up to the original points setup. Interspan sent me a wiring diagram but it does not help. I have the trigger and earth wires that come from the Interspan unit but the issue is that I have two wires coming from the points (yellow/black and white/black). Which one connects to the trigger wire. Do both connect to it ? Does one connect to it and the other is used as an earth ?
Also is the points gap and timing set as normal.

Any assistance would be greatly appreciated.
Trevor
 
Is this it?

Or.

Questions

Installing or trouble shooting your Interspan Electronic Ignition System. Find the solution below Installation sheets for IS rechargeable Batterie Systems...
interspan-ignition.com interspan-ignition.com

Cobra Classics said:
Which one connects to the trigger wire. Do both connect to it ? Does one connect to it and the other is used as an earth ?
Click to expand...
Cobra Classics said:
Interspan sent me a wiring diagram but it does not help.
Click to expand...


If you connect white to one set of points, it should only fire one cylinder (presumably with a wasted spark on the other) unless a double-lobe points cam is fitted. Maybe get in contact with Interspan again and ask them how the unit should be connected to the points?
 
I've run interspan for nearly 30 years. I've never seen a wiring diagram showing points lol.
Good luck with getting hold of Fred! I would be grateful if you do to know if he is well.
Please look up Linda Holdsworth on Facebook, her bio will say office manager at Nourish racing. She will be able to help you if anyone can.
 
If the bike is ever to be raced again, the ignition system is a critical component. The tuning depends on the balance between comp. ratio, fuel octane rating and composition, ignition advance, exhaust system and the jetting. If the ignition timing is unreliable and the other factors are constant, changing the jetting to tune the bike becomes a waste of time.
 
Sadly, I do not believe that Fred is well Chris, or that he will return to work again.

And I too have never seen an Interspan triggered by points!

Is it doable ??
 
I use a fixed timing Boyer ignition system. It never changes, and I avoid moving the rotor on it's shaft. If I do that, then I need to check the jetting. Best power is when jetting is just slightly on the rich side of the point at which destruction will occur. You cannot afford unreliable ignition timing, if you race. It is one of the differences between a road bike and a race bike.
 
Interspan has its own internal battery and internal electronics. It’s a very simple setup with a simple ground and trigger wire from the trigger assembly and fixed plug leads from the brain box. I presume your system came with a magnetic rotor and trigger that comes off the cam and sends a signal to the unit. No power from the bike (nor from the original points) would be used - rechargeable internal battery. I have run them on Nourish engine bikes. As Chris mentioned, Dave Nourish loved them. (I ultimately switched to a different programmable ignition). If I remember they fire 2x per cam revolution and are not wasted spark.

I’m out of the country until next week but would be glad to pull out an old system then and guide you if you can’t get it sorted by then.

Kenny
 
L.A.B. said:
Is this it?

Or.

Questions

Installing or trouble shooting your Interspan Electronic Ignition System. Find the solution below Installation sheets for IS rechargeable Batterie Systems...
interspan-ignition.com interspan-ignition.com





If you connect white to one set of points, it should only fire one cylinder (presumably with a wasted spark on the other) unless a double-lobe points cam is fitted. Maybe get in contact with Interspan again and ask them how the unit should be connected to the points?
Click to expand...
Yes, its the one in the linked diagram. Unfortunately it doesn't give any detail and if only one wire (or both) from the points is connected to the trigger.
 
Holmeslice said:
Interspan has its own internal battery and internal electronics. It’s a very simple setup with a simple ground and trigger wire from the trigger assembly and fixed plug leads from the brain box. I presume your system came with a magnetic rotor and trigger that comes off the cam and sends a signal to the unit. No power from the bike (nor from the original points) would be used - rechargeable internal battery. I have run them on Nourish engine bikes. As Chris mentioned, Dave Nourish loved them. (I ultimately switched to a different programmable ignition). If I remember they fire 2x per cam revolution and are not wasted spark.

I’m out of the country until next week but would be glad to pull out an old system then and guide you if you can’t get it sorted by then.

Kenny
Click to expand...
The system setup has the original points in place. Apparently this was an option back in the day. Unfortunately when the bike came to us any link wires between the two wires coming from each of the points and the trigger wire coming from the "brain" where missing.
 
I see. So the points are sending trigger pulses back to the brain. There is a multi pin harness with the units I have - I could give a pinout and perhaps you could fashion up the trigger lead from the points back to the brain easily enough. (Assuming I’m understanding this older system’s setup correctly).

Kenny
 
As the engine has the original point cam it will only have one lobe. In that case both wires will need to be connected to provide a spark for each cylinder.
 
If the owner did not go for the Interspan Trigger System, you can use the original points.
In this scenario, you wire Black/Yellow and Black/White together and connect them both to the White cable that goes into the Interspan 8-pin connector

This mimics the single sender and two magnet configuration of the Interspan "contact-less" setup.

Interspans are brilliant and simple units, so avoid swapping it for anything else unless it is broken.
 
gforce said:
If the owner did not go for the Interspan Trigger System, you can use the original points.
In this scenario, you wire Black/Yellow and Black/White together and connect them both to the White cable that goes into the Interspan 8-pin connector

This mimics the single sender and two magnet configuration of the Interspan "contact-less" setup.

Interspans are brilliant and simple units, so avoid swapping it for anything else unless it is broken.
Click to expand...
That sounds practical, I think this is the way to go. On Interspans "Universal" installation sheet it mentions trigger rotor set at 32 degrees TDC. With using the points setup I presume the standard 28 degrees at full advance is okay?
 
Ignore the 32 degrees TDC that's a marking on the rotor to make setting up easy. I marked my own as they were Triumph units & the opposite rotation to Nortons. I run 27 degrees now on the 960. Ps my units are original green fronts & yellow fronts (longer duration, TT etc. Later red front units changed voltage. I've never seen the red fully charged light! Lol something I asked Fred about for years.
 

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