Boyer Mk III no spark

Status
Not open for further replies.
Joined
May 23, 2010
Messages
283
Country flag
Hi,

I have a Boyer Mk III on my 73 850. The last time I rode the bike months ago it was missing a bit with a Boyer pickup plate that I'd added homemade lead wires to. On that pickup plate I had unsoldered the original leads and replaced them with screwed on wires with ring terminals, etc. as I'd heard recommended several times on various forums, etc. I did this because I was getting an intermittent misfire.

When I went to investigate things I noticed that I was getting sparks when I wiggled the leadwires and figured I had a bad crimp in there and so removed both leadwires and recrimped all the connections.

After reinstalling the recrimped pickup plate I'm not getting any spark when kicking the bike over with the spark plugs out. If I disconnect the points wires from the pick up plate and touch the ends together I get a spark every time.

I tried putting on a spare pickup plate (actually the original pickup plate that I ran on the bike for 90,000+ miles) that I'd pulled off the bike 5 years ago. I had pulled it off because I was getting an intermittent misfire and putting on my then unused spare pickup plate (the pickup plate that I've attached new leadwires using screws, etc. now) This had cured the misfire then.

I get absolutely no spark with that pickup plate either. It was working five years ago, I was just getting an intermittent miss while riding the bike. I also put on my spare unused rotor and the results are the same.

It seems both pickup plates are totally dead? I'm thinking about buying a spare pickup plate, but it seems unlikely that both pickup plates would totally die like this. I can't think of any other way I could get a spark every time when touching the points wires together, but not at all when kicking over the bike.

Thanks,
Eric
 
Last edited:
Sounds to me like a fracture of one or both the wires and hidden under the sheathing. The ends of the broken
wire are close enough to make connection when the wire is manipulated or twisted. This is very common with
Boyers. You were right to substitute screw connectors for the solder but the damage was already done.
I used to put a piece of rubber form over the wires to minimize the shaking caused by motor vibration. if you
have any extra lead in the ignition cable, cut an inch or two off where it connects with the pick up plate and
do the connection over.
 
Temporarily run two lengths of new wire from the boyer to the coils to try and isolate the issue, more likely a fractured wire as lazyeye notes than both plates suffering the same fault
 
Last edited:
For what it's worth I get 128 ohms across the two lead wires in one pickup plate and 132 ohms across the lead wires in the other one. A fractured wire should cause infinite resistance.
 
There's a good chance that the loose connection caused the control box to have spikes it couldn't handle and it is now toast.
 
There's a good chance that the loose connection caused the control box to have spikes it couldn't handle and it is now toast.

I have a spare control box, but I wouldn't expect a spark when I touch the two points wires together if it were toast.
 
I have a spare control box, but I wouldn't expect a spark when I touch the two points wires together if it were toast.
I misunderstood which wires you were touching. The control box is probably good.
 
You mean at the headsteady? I'll take a look. It sparks good when I touch the two points wires together though.
 
Boyers need a good ground. Mike at Walridge motors can bench test the encapsulated black box for you.
 
Status
Not open for further replies.
Back
Top