Vicious kickback

The first thing that I'd do is replace the wiring from the pick-up plate. This has a particular habit of fracturing inside the insulation where it passes through the back of the timing chest. Check wiring and connectors on the pick-up plate too.

A poor signal to the 'black box' will have the same effect of throwing the unit onto full advance. Any live feed to the ignition could also be suspect.

I'd say that this has to be Boyer related. Most of us have been there and dealt with the confusing symptoms !

When my Boyer wires failed (broken wire)Ireplaced the soldered wires with spade connectors securedvia brass bolts withtwo brass nuts (using one as a locknuit). This was described either on the BI list or the oldNOC-L.

I just checked my records - that was14 years (and almost30,000 miles)ago, so it is effective (I've not touched them since). I can't remember who originally posted this fix so cannot attribute, but I'm still grateful.

As an aside, whatever happened to the NOC-L archive?

Mike

MkIII Commando

(when the wire failed I called my get you home service& they eventually appeared with a 30 foot low loader, We looked like an undecorated NVT Carnival Float and caused chaos in the Kingston one way system)

I'm struggling with an identical problem. I've strobed the timing to give 31 degrees before TDC at 5000rpm and the kickbacks are lethal, when it does start it doesn't sound or feel happy (nor do I) and appears to be massively over advanced, retarding the ign by eye solves the problem so it would seem the strobing technique is going wrong somewhere, (good battery, timing marks correct etc.) I have modded the Boyer back plate to fit a better wire to the black box, I'm beginning to think that is where the fault lies as that was the last thing I changed. Got to be hasn't it?

Just re-read your post and my mod involves a screw through the back plate to attatch a chocolate block type connector. I bet that, and your brass screws is bug---ing up the signal.

Hot off the press. Just de-modded the back plate and set the timing statically. Starts without kicking back, I'll strobe it later to 5000rpm when everybodies kids are in bed and report back

I have tried Boyer ignition on Commandos, and when they ran they ran well. In every case though, I ended up returning to the original factory points system. The points and mechanical auto advance do require occasional maintenance, but they are extremely reliable and can usually be fixed if there is a problem.

I well remember the morning of 1st January 1978 taking a bag of tools and the original ignition from my 850 MkIIa on a bus to the outskirts of Newcastle so I could fit them to replace the Boyer which failed on new year's eve.

Alan, NOC-L was the old NOC bulletin board, faded away a while ago.

BI is the Brit-Iron List, here:https://list.indiana.edu/sympa/info/brit-iron-l

Also useful is http://www.accessnorton.com/(you may already know of this one)

I don't have a copy of the original ost (it was in 1999), the fix involved drilling the backplate of the Boyer to take 2 small bolts, soldering a tag onto the end of the boyer pickup wires (drilled to accept the screws) and then bolting the whole thing up (I put 2 nuts on each bolt & added small washers to ensure good contact). The whole process took about 30 minutes. Oh, I also added a piece of foam to help damp down any vibration in the area. I've not had any further problems with the ignition.

I took a photo of my setup buit can't get the photo in via the NOC msg interface, I will email youdirectly.

Mike

MK III Commando

If the Boyer stator plate has been disconnected, it definitely needs to be connected the correct way round or the 'retard' will not work. The two wires are not left and right cylinder, as they are from a points system.

Excellent news Alan!

My Boyer backplate was replaced on 15 Sept 98 and a wirefailed on 28 June 99. That's why I went straight for thebolts

The wires to the backplate appear to become brittleat the point where the insulation ends and the wire is soldered to the backplate (lots of posts about this) , The recommendation is to add something like silicone to reduce the vibration & try toprevent this.

If anythong else goes I will probably head for a Pazon, they seem to be less sensitive to low voltage &I don't recall seeing any material failures/issues to date (I'm sure somebody will correct me if thi sis incorrect )

Mike

MK III

Alan, now that you've dealt with the symptoms, you'll know immediately next time.

The wiring that you have with connectors mid-way is really not ideal. The Commando engine leaps around on the isolastics so the wiring is being pulled back and forth.

I'd be inclined to re-wire it from pick-up to ignition unit. I use two-core household cable with moulded insulation which gives some extra support to the individual wires, run loosely through rubber cable ties - not too tightly clamped to the frame.

To go back to my mod, I soldered two pieces of solid copper wires (sleeved) to the printed circuit board and routed them across to the opposite side where I had them attached to a chocolate block type connector which itself was screwed to the PCB with a 3mm screw, the wires were about 40mm long. I'm guessing the length of these wires and their routing was compromising the timing signal. Once it was all returned to something resembling original, my problem went away. I don't think soldering copper wire makes it brittle, but the multi strands become one and are then prone to fracture when vibration is an issue.

Just posting a pic of the boyer fix in case it can help anybody else out...

Mike

Chaps, do NOT solder any multistrand copper wire that will be subject to vibration. It WILL fail, and when it breaks will depend on how much vibration it is subject to. I wrote about this in a thread last year, but to repeat briefly: Multi strand copper wire is semi-annealed. When you apply solder you temper (soften) the portion immediately adjacent to the edge of the solder. When the wire vibrates the movement is focused on the softest part that then work hardens and breaks. It is to do with the fact that metals are crystal structures that are (usually) in unstable states and will readily reconfigure to a new structure. The solder stress is why the original Boyer cable pick-up plate connections failed; the silicone glue and cable tie fix tries to stop them moving. When Britain made missiles in the 1960-70s the soldering of wires was forbidden, I daresay anyone who works in the aerospace industry will tell of similar rules.

Previously Chris Grimmett wrote:

Previously richard_payne wrote:

I'd be inclined to re-wire it from pick-up to ignition unit. I use two-core household cable with moulded insulation which gives some extra support to the individual wires, run loosely through rubber cable ties - not too tightly clamped to the frame.

Richard,

How could you say such a thing? We have been told that it is heresy, I quote from the NOC's electrical guru in a recent conversation:-

"But the use of any old trailer cable and/or mains cable on any vehicle is rubbish!!. I would use none of the above cables on a British Vehicle (well perhasp to lash up some speakers on a 70s car!) Cable is relativle cheap, 90% of the cables on a British motorcycle have the same current capacity so choosing correct vehicle wiring does a correct job. Every time you add wrong/different coloured cable to your bike you multiply the chances of the next breakdown sort out being horrendous. Casual wiring gives casual results. DO IT PROPERLY!"

Crikey Chris, I'm in trouble now. Actually I'm a stickler for correct colours (even down to the 16H being wired entirely in black, as original - not too much of a problem as I know where all the wires go).

However, in the case of the pick-up lead, and after the inevitable failure, I took the view that a two-core with moulded outer insulation gave better support to the inner cable than two separate cables in a loose tube that always seems to have water in it. So far, I seem to have been proved correct and the eighteen-inch section of odd colours seems a small price to pay.

I promise not to go to Norfolk though.