Carb Tuning

Every now and then we get a query that is well worth relaying to other readers and customers, this one from John Blozies is one such question:

"Stephen,

The new Tri-Spark ignition you sent is great. I've related my experience to other Norton fans via the INAO website/"chat room".
Now, however, I have one question for you:
In tuning/setting the carburettors of these venerable twins equipped with dual carburettors, it is customary to fire one cylinder at a time and get the best carb setting, then go to the other side and do the same. When pulling a sparking plug wire off so's to run just on one side, the Boyer rumor was to ground out the spark otherwise it would harm the Boyer.
I'm using a Dyna dual lead coil with your Tri-Spark. Will it do any harm to temporarily pull one sparking plug wire while adjusting the running side carburettor?
Thanks again for a fine product. I'll forward a note sent to fellow Nortoneers here in the States.

Thank you,
John Bloszies
Seale, Alabama"

Below is the response we would like to share with you all, along with a shot of John's Commando. Remember, it's always best to ask if in any doubt!

"Hello John,
This is good question and one I would like to include on our website.
With your permission and a perhaps a picture of your bike?

If you must remove one plug lead always have this grounded to a spark plug on the cylinder head. Unplugging the spark plug lead with the engine running will stress any ignition system including points. I've seen arcing across the top of the coil in some case and this can really stress electronic ignition.

Hope that helps,
Steve"