1978 R80/7 Engine keeps going

[jackonz]

Well after getting the bike back together today I fired it up for the first time in nearly 2 years, it went and ran on the second try and with a few small adjustments on the carbs I had it settled in to a nice idle, then went to stop the motor on the kill switch and it kept going?
So then I tried the the ignition key and it still kept running but with the rev counter slammed right round the dial, so turned ignition back on and tried several more times with the kill switch and it shut down.

I re started the bike and the same thing happened again, now I was very careful when I stripped the bike down labelling every connection and double checking on re connecting things with the only thing wrong being the stop and tail light wires mixed up.

What I did change from old to new was the voltage regulator and the starter relay, I wonder if there is something there that is causing the problem.

Aside from that all that is different from standard is the Boyer Ignition system that was on the bike when I got it and it ran fine.

Any ideas please.

[Rob Frankham]

Well after getting the bike back together today I fired it up for the first time in nearly 2 years, it went and ran on the second try and with a few small adjustments on the carbs I had it settled in to a nice idle, then went to stop the motor on the kill switch and it kept going?
So then I tried the the ignition key and it still kept running but with the rev counter slammed right round the dial, so turned ignition back on and tried several more times with the kill switch and it shut down.

I re started the bike and the same thing happened again, now I was very careful when I stripped the bike down labelling every connection and double checking on re connecting things with the only thing wrong being the stop and tail light wires mixed up.

What I did change from old to new was the voltage regulator and the starter relay, I wonder if there is something there that is causing the problem.

Aside from that all that is different from standard is the Boyer Ignition system that was on the bike when I got it and it ran fine.

Any ideas please.

Running on is a known issue with Boyer ignition, so much so that they issued a note suggesting a 'fix'. The original wiring has the positive side of the left hand coil wired direct via a fuse to the battery with the green/blue wire (originally connected to the coil) being used to power the control unit. The revised wiring returns the green/blue wire to the coil and takes a feed from that terminal to the control unit. Attached is the BB wiring diagrams from their original Instruction sheet.

revised wiring.jpg (163.25 KiB) Viewed 1316 times

This sounds very much like the issue you are experiencing... as to why it wasn't happening before, no idea!

Rob

[gspd]

So then I tried the the ignition key and it still kept running but with the rev counter slammed right round the dial, so turned ignition back on and tried several more times with the kill switch and it shut down.

Some aftermarket ignitions require holding the front brake on while turning off the key or kill switch to get the engine to stop.
Not sure why. Some type of safety feature I presume?

EDIT : re-read Rob F's rewiring explanation and instructions, makes sense now.

Also, inspect and clean the contacts in the kill switch with contact cleaner and compressed air.
Corrosion in the kill switch can wreak havoc and may also explain the tach freak out.

[barryh]

Some aftermarket ignitions require holding the front brake on while turning off the key or kill switch to get the engine to stop.
Not sure why. Some type of safety feature I presume?

And there was me thinking it was just rubbish design on Boyers account.

[ME 109]

I recall something from Boxerworks years ago about powering up the rear brake switch to power the ignition. A method of hot wiring?

[jackonz]

Well after getting the bike back together today I fired it up for the first time in nearly 2 years, it went and ran on the second try and with a few small adjustments on the carbs I had it settled in to a nice idle, then went to stop the motor on the kill switch and it kept going?
So then I tried the the ignition key and it still kept running but with the rev counter slammed right round the dial, so turned ignition back on and tried several more times with the kill switch and it shut down.

I re started the bike and the same thing happened again, now I was very careful when I stripped the bike down labelling every connection and double checking on re connecting things with the only thing wrong being the stop and tail light wires mixed up.

What I did change from old to new was the voltage regulator and the starter relay, I wonder if there is something there that is causing the problem.

Aside from that all that is different from standard is the Boyer Ignition system that was on the bike when I got it and it ran fine.

Any ideas please.

Running on is a known issue with Boyer ignition, so much so that they issued a note suggesting a 'fix'. The original wiring has the positive side of the left hand coil wired direct via a fuse to the battery with the green/blue wire (originally connected to the coil) being used to power the control unit. The revised wiring returns the green/blue wire to the coil and takes a feed from that terminal to the control unit. Attached is the BB wiring diagrams from their original Instruction sheet.



revised wiring.jpg



This sounds very much like the issue you are experiencing... as to why it wasn't happening before, no idea!

Rob

Thanks Rob, I will look at it this weekend. I did find an old document amongst all the paperwork and manuals I got with the bike and one was for the Boyer unit and it mentions exactly what you said, but no drawing to go with it but did mention the cause being to do with a small amount of current needed to run the ignition will keep the bike running.
I can only assume that all the work I did on cleaning the electrical connections on the bike has made it possible for this to happen, will keep you posted.

Cheers

[Rob Frankham]

The truth is this shouldn't happen when the power is switched off, there should be no path for even the minimal current required to run the unit... however, clearly it happened often enough for the manufacturer to issue the note giving the work around. It is interesting to note that the instructions for later models of BB ignition don't have the coil positive connected direct to battery but connected through the igition switch as in the note. While I understand the reasons for running the coil current direct from the battery, I wouldn't be very comfortable with it since it relies on the electronics of the ignition unit to 'switch' the bike off completely.

In practical terms, rewiring the ignition in line with the note, although it will solve the immediate probolem, will not necessarily fix the parasitic current drain that is causing the issue and I would be troubleshooting the electrical system on the bike to see if I can trace the source of that parasitic drain.

Rob

[jackonz]

The truth is this shouldn't happen when the power is switched off, there should be no path for even the minimal current required to run the unit... however, clearly it happened often enough for the manufacturer to issue the note giving the work around. It is interesting to note that the instructions for later models of BB ignition don't have the coil positive connected direct to battery but connected through the igition switch as in the note. While I understand the reasons for running the coil current direct from the battery, I wouldn't be very comfortable with it since it relies on the electronics of the ignition unit to 'switch' the bike off completely.

In practical terms, rewiring the ignition in line with the note, although it will solve the immediate probolem, will not necessarily fix the parasitic current drain that is causing the issue and I would be troubleshooting the electrical system on the bike to see if I can trace the source of that parasitic drain.

Rob

Hi Again, so I have fixed the problem and now the kill switch and ignition key will stop the motor as it should, as to why it was keeping running now after the rebuild (or really re commissioning) I am unsure.

I did some tests but first I should point out that the bike is not fitted with twin coils as per the drawing but a single pack 12v coil with 2 HT leads, would that make a difference I have no idea, so I measured the current draw from the Battery + to the coil on the red connection with everything else off and had a 0.02 amp draw, then I disconnected the Green wire that feeds the electronics box to see if the key was leaking power and letting it run I got a total zero.

So I rewired it as per the second circuit feeding the coil and the electronics from the green ignition wire and it worked perfectly.

As to why it is now different to when I rode the bike 2 miles when I picked up the bike to now is a bit puzzling, could it have been a bad earth or that fuse link (red cable) I replaced who knows, all I know now is it works and I am chuffed.

Now all I need to do is paint the tank and front guard and its finished for now.

Thanks for your assistance Rob.

[Rob Frankham]

No worries, glad I was able to help...

Rob