Boyer question

SteveBorland · Oct 28, 2015

I'm hoping that someone here can offer some good advice on a slightly puzzling problem I'm having.
Background is that it's an 850 MkIIa with a Boyer. Since I put in on the road this year, its been running well, if slightly leaky. Then it started cutting out, seemingly related to engine speed - i.e. it would idle fine, but riding at around 2000 - 2500 rpm, the motor would occasionally just die. pulling the clutch in and letting it out while giving it a bit more throttle would sometimes get it going, occasionally I would have to stop and fiddle with the carbs, then it would start up normally.
Last time I went out to go for a ride, it would not start at all. I traced it to a total lack of spark, so did the normal routine of trying another battery, checking for continuity, etc. Then I did the test of touching the input leads from the sensor on the cam together, which should produce sparks - it does not.

Things are pointing to a Boyer failure, but having read many threads on this over the last 20 years, I'm not certain. The previous owner was clued up regarding Boyers, and has done the anti vibration fix using silicon sealer on the sensor plate. I cannot find any sign of wiring damage as I flex the cables from the sensor plate.

Thinking about the symptoms, it seems to be an intermittent failure that's become more permanent, which is why I'm looking at the wiring. It's possible that one or both coils are dead, so I plan to try another coil this weekend.

Anything else I can try while i'm fiddling about?

worntorn · Oct 28, 2015

Have you determined that power is getting to the Boyer?
A temporary wire directly from battery post to the unit is probably the quickest and best way to rule out a problem in the power supply to the unit. Also make sure the ground is clean and good or add a new temporary one to be sure.

Glen

Torontonian · Oct 28, 2015

Yes there is. Your Kill switch on handlebar controls needs to be taken apart ,the contact points cleaned with a little emery paper . At the same time inspect the ground , unscrew whatever bolt holds it to the frame and clean that up of all rust and oxidations . A little oxyguard paste at these spots helps prevent future issues. Are the battery bolts clean and tight ? Clean fuse contacts too. I doubt it's coils but no harm in cleaning those contacts too. Have fun tracing.

concours · Oct 28, 2015

SteveBorland said:
I'm hoping that someone here can offer some good advice on a slightly puzzling problem I'm having.
Background is that it's an 850 MkIIa with a Boyer. Since I put in on the road this year, its been running well, if slightly leaky. Then it started cutting out, seemingly related to engine speed - i.e. it would idle fine, but riding at around 2000 - 2500 rpm, the motor would occasionally just die. pulling the clutch in and letting it out while giving it a bit more throttle would sometimes get it going, occasionally I would have to stop and fiddle with the carbs, then it would start up normally.
Last time I went out to go for a ride, it would not start at all. I traced it to a total lack of spark, so did the normal routine of trying another battery, checking for continuity, etc. Then I did the test of touching the input leads from the sensor on the cam together, which should produce sparks - it does not.

Things are pointing to a Boyer failure, but having read many threads on this over the last 20 years, I'm not certain. The previous owner was clued up regarding Boyers, and has done the anti vibration fix using silicon sealer on the sensor plate. I cannot find any sign of wiring damage as I flex the cables from the sensor plate.

Thinking about the symptoms, it seems to be an intermittent failure that's become more permanent, which is why I'm looking at the wiring. It's possible that one or both coils are dead, so I plan to try another coil this weekend.

Anything else I can try while i'm fiddling about?

Revisit the sensor plate wiring. Mine had broken with no outward signs. Very intermittent. Wiggle thise wires while it's running. Also temporary substitute new wires that exit the engine, run up along the frame.

SteveBorland · Oct 28, 2015

Sorry, forgot to mention that yes, there is power to the boyer and no, there is no kill switch

.. its wired direct from the ignition switch. Good earths everywhere as well.

Cheers,
Steve.

Torontonian · Oct 28, 2015

Take apart the ign. switch and clean contacts. After all it's 43 years old.

peter12 · Oct 28, 2015

Boyer ignition needs good battery power. If you swapped the battery for another used one I wouldn't take anything for granted. Charge the battery fully, if you have not done so and start from there.

SteveBorland · Oct 28, 2015

Thanks for the input. The ignition switch has been cleaned and reassembled, the 2nd battery was a new Lithium Iron type, fully charged. Don't recall the exact voltage reading on the input to the Boyer but it was over 13V.

I will recheck the pickup wiring, but I'm a bit sceptical of this, seeing as the unit does not produce sparks when I touch the 2 pickup wires together several times in succession....

kommando · Oct 28, 2015

Check the earth route from the boyer back to the battery and from the engine to battery.

Torontonian · Oct 28, 2015

Bad or sketchy grounds are the big killer of Boyers. The trigger diode (encapsulated) fails. Walridge Motors has a bench-test service if all else fails.

concours · Oct 28, 2015

SteveBorland said:
I will recheck the pickup wiring, but I'm a bit sceptical of this, seeing as the unit does not produce sparks when I touch the 2 pickup wires together several times in succession....

Missed it.

To test, run a desicated test lead from the battery to the Boyer. Same with the ground.

Torontonian · Oct 28, 2015

Running a desicated wire would surely be a boo-boo. Dried up and cracking insulation. I'm certain the word is dedicated. Yes , just bypass potential join points and switches etc. by direct wires for your testing /eliminating problems purposes. Kinda fun with an "AHA !" when the revelation occurs . :shock:

JimC · Oct 28, 2015

Visually inspecting the Boyer pickup coils wires will not find the fault. Use an ohm meter and twist, shake those wires. You won't find a break in the insulation. The wire will be fractured inside the insulation. Usually the fracture will not open below 3,000 rpm or so, resulting in the engine running fine below that rpm. Trouble starts at higher rpm when the frequency of vibration cause the fracture to widen, causing one cylinder to misfire or both cylinders to misfire if both wires are fractured.

The wires I'm referring to are the ones that are soldered to the Boyer coils themselves. I think they are insulated 16 ga. wires. As for the coils themselves, I've never heard of those failing. The problem with the Boyer is soldering those wires to the pickup coils. The solder turns the stranded wire into solid wire for a short distance. Vibration causes the wires to flex and the solid soldered portion will, and does, fracture. Affixing these wires to the pickup plate with silicone will not stop the vibration from causing a fracturing. Desolder those wires and connect with a small screw/nut and a ring connector. DO NOT SOLDER, CRIMP ONLY!

Torontonian · Oct 28, 2015

Yup ,take a knife and start digging away encapsulation material if so.

SteveBorland · Oct 29, 2015

Thanks to all for some helpful ideas. I´ll try these & report back later.

Torontonian · Oct 29, 2015

Let's rethink this. Obviously you don't even need the transistorized pickup plate at all for a test. Just touch the 2 wires to it together and there should be spark occurring at the plugs. The plugs are pulled from the head and clamped to the head to ground them and enable viewing for spark.The white wire to the Boyer black box is your power source so run a test wire from Battery negative (power) to the Boyer white. Try your 2 wire touch test again. If nothing then the next step is coils wire inspections. Hopefully you are aware the coil clamps exert a very low torque clamping force . If overtightened the coil outer casing can crush creating problems too. 12 or 6 V. coils ?

Boyer question

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