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Dual point dual coil ignition from Commando

Glenliman

Well Known and Active Website User
VOC Member
My Rapide has a dual point setup which uses Norton Commando ignition parts along with what appears to be a homebuilt housing. This has been a very good ignition unit for most of the 20,000 or so miles I have ridden the bike. I have not had to fiddle with the points in all of that distance. Starting is very easy. On a couple of occasions after stroking the bike thru without the key on, then turning the key on, the bike has auto started.
Normally it starts in one easy kick.

The Lucas points in the unit were starting to get a bit worn so I replaced them with some Japanese Daichi units I purchased locally at British /Italian motorcycles. The owner of British/Italian is a long time Commando sufferer and generally knows his stuff on Nortons. He claimed the Daichi/ lucas pattern points were high quality unlike the Chinese knockoffs he stocked at one time.

On a recent 800 mile round trip these points failed and caused considerable difficulty. At about the 350 mile mark the front cylinder stopped firing at anything below about 2800 RPM. I had lots of help with the bike at the rally, but unfortunately noone was familiar with this particular ignition setup, which I suspect was made in very small numbers in a shed somewhere in the UK back in the late seventies.
We spent quite a bit of time fiddling with and removing carbs, checking Valve timing, compression etc, all of the things you do when a bike is not running properly. The point gaps were at about 20 thou, a little narrower than I recalled setting them initially , but considerably wider than magneto point gap. Consensus was that if anything, the gap was too wide.

I had initially set the Daichi ponts at 25 thou since that was about what the Lucas point gaps were when I bought the bike, and I have no other information about the ignition system.
The previous owner had ridden the bike for ten years thinking it had Capacitor discharge ignition, so that gives some idea of how well these lucas points last. I recall he told me "you'll love this modern CD ignition, it starts every time in one or two kicks!" The one or two kicks part was accurate at least.

In the end we gave up on getting the bike going and found a ride home for it.
The next day, due to border problems, my ride did not materialize so I found myself alone with no option except to try again to fix the bike. After staring at it for about twenty minutes I decided to kick it over while watching the ammeter. I noticed that the ammeter did not bounce from discharge to zero as it normally should when the bike is kicked over.
I opened the point gaps to about 25 thou by eye and the bike started easily on two cylinders.


It turns out that the heels of the Daichi points were wearing very quickly causing the point gap to decrease, which in turn robbed spark from the front cylinder. When the gap diminishes enough, the spot where both sets of points are open briefly (0 discharge on the ammeter) disappears and the ammeter shows constant discharge. When this occurs the spark to the front cylinder becomes very weak and will not fire under compression. Obviously timing is also thrown off as the heels wear and the gap closes.
On the trip home the bike went back onto one cylinder twice. Each time I stopped and opened the points a little, which restored firing on the front cylinder.

Has anyone else here run this system and encountered this problem?

I have since located some new old stock Lucas 10 ca points and installed them. The bike starts and runs great again.
 

vapide

Well Known and Active Website User
Non-VOC Member
I've run into this over the years a couple of times on machines where someone put in new points without lubing them. A lot of people are so unfamiliar with points now that they figure while they have them out the out to give the distributor a good cleaning, so they wipe it clean or blast it with electromotive cleaner, then put the new points in dry. I had a Corvair auto once that wore out the points in about 250 miles for that reason.
 

Glenliman

Well Known and Active Website User
VOC Member
Lube was not the problem, the points came with a new felt which I soaked in lube and installed. I pretty much grew up with breaker point ignition on everything so I'm somewhat familiar with it but I do not recall point heels wearing this quickly.
I have heard some of the members with series D ignition complain of this same problem with replacement points. The anwer for that setup seems to be in locating NOS points with tufnol heels. The NOS Lucas 10CA points are plastic, but it is obviously the right kind of plastic for the job.
 

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