1968 Commando Boyer Bransden Setting

Ok here's one for all of you Norton experts out there. I have a 1968 Commando that I purchased several years ago and am just getting around to. It's actually about the 75th off the line making it really early. The problem I'm having is trying to get it going. I've done all of the Amal stuff, cleared the pilot jet, set the float level, basically rebuilt the things so I think I'm good there. It has a Boyer Bransden black box and the interesting thing I found was that the previous owner had it set so that the white dot on one of the magnets was looking through the lower hole in the plate which I thought was for Atlas timing. Not sure I understand this as I thought Atlas's had Magnetos. Regardless shouldn't the white dot on the magnet be looking through the upper hole with the crank set at 31 degrees BTDC on the right cylinder? I assume that all Commandos had the same timing? Thanks all

Welcome jms696969run,

The white dot should be lined up with the lower (Atlas) hole in the Boyer pickup plate for the initial static 31 degrees BTDC setting, as your Commando is a very early one, so it should have a "20M3" engine prefix? And presumably, it still has the chain driven points housing behind the barrels in the old "magneto" position? So the Boyer rotor needs to be set for clockwise rotation, which is the opposite way to later Commandos with a 20M3S prefix (and subsequent models without the prefix) that had the AAU and points at the end of the camshaft, thus the AAU or Boyer rotor on those models rotates anti/counter clockwise.
http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf

Unfortunately, the Boyer instructions fail to mention the 20M3 Commandos also needs to use the lower (Atlas) timing hole.

Not all Atlases had a magneto, [Edit] some late ones had the points housing in place of the magneto with a capacitor-coil ignition system, - apparently.

L.A.B.
Thanks for the reply. It does seem like a rather important ommission on Boyer's part, but good news to get that straightened out, guess I'll have to look for the problem elsewhere.

Are you actually getting sparks at the plugs?

L.A.B.
There is spark. Do black boxes ever go bad? How about carb jset up. The Amal Concentrics that are on it have the pressed in pilots and they appear to be .016 in diameter because I cleared one of them. I thought that was going to solve the problem. I am trying to run it on what I think is a 25 pilot, middle posistion on the needle, 220 mains, and a 3 slide. Very little perceptible play in the slides within the body. All new gaskets and airscrews with o rings. I forgot to mention in the "Atlas" timing mode I was able to start it but ran very rough and was spitting back through the carbs and backfiring (visable flames) through the muffler. Could it be plugs that are just old and need replacement. I've never been able to get a stobe on it in time before it stalled

It sounds like a classic Boyer low voltage scenario !

I would try giving the battery a good charge and checking all connections. Make sure that you're getting 12.5v at the ignition.

jms696969run said:

There is spark. Do black boxes ever go bad?

Click to expand...

Yes, both the box and the pickup coils can fail, but many electronic ignition problems are due to bad wiring connections and faulty switches?
The soldered joints where the wires connect to the pickup plate is a common failure point. Also check you have the two pickup wires connected the correct way around, as connecting them the wrong way around puts the ignition timing way off, and the ignition timing will not advance.

http://www.boyerbransden.com/faultfinding.html


http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html



I would certainly fit a new set of plugs.

Thanks 79x100 I'll check it out.

Also make sure you have a good ground wire connection between the engine and the harness (Red) return wire back to the battery?
As the plugs also need to ground, and the Commando's rubber Isolastic mounts make poor electrical conductors.