GS750 with Boyer Ignition - keeps cutting out

[londonboards]

GS750 with Boyer Branson electronic ignition, has now started cutting out.

This mostly happens on start up. Starts up really good, then within a minute, shuts down dead - complete cut out. All other electrics still working. But if you turn the kill switch off and back on, it starts immediately, runs for a while and does it again. Does this 3 or 4 times whilst warming up, then runs fine with no problems. Maybe the occasional cut out on a journey but it's always fixed by flicking the kill switch on and off.

After it cuts sometimes, when you flick the kill switch back on and the power runs back into the coils, if fires on one cylinder. This tells me the problem is 100% electrical.

I'm thinking the Boyer unit is playing up. Weird that it's only when cold though. And that you can fix the issue by turning the kill switch off and on again.

Any ideas?

 

[standswithabeer]

jump the kill switch and see what happens

 

[posplayr]

jump the kill switch and see what happens

and get some contact cleaner for that seotch

 

[Big T]

I agree, start with the kill switch.
Unplug the right handlebar pod in the headlight and remove it.
Inspect it, then put it in a gallon zip lock and disassemble the kill switch, check the connections and clean the contacts.

After that, clean the starter button while you're in there.

The vintage Boyer s are known to fail

But, I'm puzzled how it can start on one cylinder.

 

[londonboards]

No it doesn't start, it just fires once on the one cylinder that has fuel under compression. When you turn to the kill switch back on (and without hitting the starter), the current sparks the plug and fires the one cylinder for one instance.

The point being that, turning the kill switch on and off again, seems to fix the problem until it happens again.

But one it's warmed up it doesn't happen. Just don't know how warming the bike up can make a difference to the kill switch working or not working.

I'm thinking more along the lines of the Boyer ignition.

 

[posplayr]

No it doesn't start, it just fires once on the one cylinder that has fuel under compression. When you turn to the kill switch back on (and without hitting the starter), the current sparks the plug and fires the one cylinder for one instance.

The point being that, turning the kill switch on and off again, seems to fix the problem until it happens again.

But one it's warmed up it doesn't happen. Just don't know how warming the bike up can make a difference to the kill switch working or not working.

I'm thinking more along the lines of the Boyer ignition.

You eliminate the obvious or easy to fix. If it is the Boyer you have a bigger problem.

That said your symptoms sound more like a switch, as electronics tends to heat and fail and not come on until cooled and not just on-off cycle.

 

[sam000lee]

No it doesn't start, it just fires once on the one cylinder that has fuel under compression. When you turn to the kill switch back on (and without hitting the starter), the current sparks the plug and fires the one cylinder for one instance.

This started happening to my GS750 after I installed a Dyna ignition and coils. Runs great otherwise but I've been wondering why it did this ever since...

 

[posplayr]

This started happening to my GS750 after I installed a Dyna ignition and coils. Runs great otherwise but I've been wondering why it did this ever since...

There was a thread about an aftermarket ignition upgrade with funny behavior.

It seems it was fixed by changing plug wires or spark plugs to resistor type. This would lead one to believe it was a crappy ignition design that was very sensitive to the secondary circuits of the coil.

I think the bike would run, but only up to a certain RPM and lose power.

 

[GregT]

First check your HT leads. You should have 5K ohm caps in good condition. I'd ohm them to be sure they're in spec.
Next check the system has a good earth...
Then test the voltage at the ignition unit - hook up a voltmeter or lamp and turn the bars/wriggle wiring to check supply is continuous. Particularly the kill switch wiring....

 

[Gorminrider]

There was a thread about an aftermarket ignition upgrade with funny behavior.

I was thinking that too... it's here https://www.thegsresources.com/_forum/showthread.php?253875-Engine-dies-randomly-while-riding

It's the usual mess- I'd read the first post then go straight to the last and read them backwards (I always do this when I'm hunting old posts) but happily solved by mcquillr using resistance plugs AND resistance caps.

 

[posplayr]

I was thinking that too... it's here https://www.thegsresources.com/_forum/showthread.php?253875-Engine-dies-randomly-while-riding

It's the usual mess- I'd read the first post then go straight to the last and read them backwards (I always do this when I'm hunting old posts) but happily solved by mcquillr using resistance plugs AND resistance caps.

I start at the bottom as well and only after a week or two of controversy and raging debate about which way to connect a battery or clean a switch.
After that and no solution, the OP usually listens.

 

[mcquillr]

I was thinking that too... it's here https://www.thegsresources.com/_forum/showthread.php?253875-Engine-dies-randomly-while-riding

It's the usual mess- I'd read the first post then go straight to the last and read them backwards (I always do this when I'm hunting old posts) but happily solved by mcquillr using resistance plugs AND resistance caps.

I’m just seeing this now. This problem does seem similar to mine however to restart my bike I needed to turn the ignition switch off and then on (likely to restart the Boyer system). Try the resistor plugs and caps and see (cheap fix) but this problem sounds maybe a little bit different that mine unless your kill switch also mills power to the Boyer unit.