Starting problem, no spark

[rustybronco]

Check the voltage at the coils with just the key on and again when cranking.
if the voltage is above say 11.0 volts when cranking, then...
what is the resistance of the coils on the primary and secondary side and the resistance of the plug wires/caps if they are the type that can be removed.

I suspect that if originally it would start by cranking, then it began to have problems with intermittently starting when cranking bringing you to the point of having to bump start it. the voltage at the coils has begun to drop too low and it may have continued to deteriorate.

but it's only a guess at this point until further investigation.

***EDIT***
thanks for the diagram, voltage goes from the kill switch to the coils on the B/W? wires (hard to read the color codes on the diagram).
simple system, shouldn't be to hard to get it up and running.

[geisterfahrer]

Update: It's Alive!!!

I decided to spend some time with the 650 Nighthawk today. I rechecked the coils and pickups, all tested within spec. I replaced the spark plug wires because I had a new set sitting on the shelf (I don't think that was the problem, they wouldn't all fail at once). Then I started going through the wiring harness bit by bit, connector by connector. I used my DeOxit on every junction, and thoroughly cleaned the two chassis grounds, testing for fire after every step. Still nothing. Then I pulled the clutch diode out of its socket, tested it, cleaned it, and replaced it.

A cough! By golly, she coughed! I made sure the carb bowls were full, and cranked again with the choke on, and she fired .

I put her all back together, put a half gallon of gas in the tank, and took her for a short ride around the neighborhood. She was purring like a kitten. Unfortunately, she is not licensed, registered, or insured at the moment, so I couldn't take her out for a real ride .

Anyway, I'd like to say thanks to the GSR members who gave me advice and encouragement. I still don't really understand what the clutch diode does, or why cleaning its contacts could solve an ignition issue, but there it is .

Cheers,

Kevin

[Steve]

The clutch diode is not used in the GS bikes, so I will have to guess about its function until I can look at a wiring diagram.

There are probably a couple of items that share a ground, and the diode helps sense which one.

On '82-and-newer larger GS bikes, there is a light to show that your side stand is down. It is fed by the same wire that feeds the oil pressure light. There is a diode there to keep the signals straight so that a deployed side stand does not turn on the oil pressure light.

The clutch diode on the Nighthawk might share something similar.

.

[Thomas Kenny]

What did you find on you voltage check at the coils?? Your should have 12volts with a charged battery. If not then you might have to consider a relay between the battery and the coils. My 84 Suzuki exibited the same symptoms and my voltage at the coils was only around 10 volts due to built up resistance in the old wiring harness. I installed a relay and it cured my starting problem. Just a shot in the dark. Good luck and keep us posted.

[Thomas Kenny]

Disregard my recent post.........

[geisterfahrer]

Steve,

Thanks for the explanation on the diode. After studying the schematic a little more closely, I can see that the diode allows power to the starter relay if the transmission is in neutral, otherwise the clutch switch has to be closed.

So, I guess that wasn't it after all. It only prevents the engine from cranking, it does not disable the ignition, unless there is more going on in the starter relay than is indicated by the schematic. There was never any problem cranking the engine.

I must have accidently fixed something somewhere else. I'm now thinking that having disassembled and cleaned the kill switch may have been the key, since the primary voltage to the coils goes directly through it. It was fairly dirty, and I seemed to be getting intermittent continuity through it when I tested it before cleaning.

Thanks again, everybody!

[rustybronco]

There are probably a couple of items that share a ground, and the diode helps sense which one.

There is a diode there to keep the signals straight so that a deployed side stand does not turn on the oil pressure light.

The clutch diode on the Nighthawk might share something similar.

Steve,

Thanks for the explanation on the diode. After studying the schematic a little more closely, I can see that the diode allows power to the starter relay if the transmission is in neutral, otherwise the clutch switch has to be closed.

geisterfahrer,
the clutch switch is on the ground side, and I suspect, the diode is for the grounds on the neutral light, gear position indicator, and the gear position switch. BUT I cannot read the components, in the starter relay.
you can remove the diode, that will give you the answer.

[geisterfahrer]

BUT I cannot read the components, in the starter relay.

rusty, the diagram in the Clymer manual is not much clearer than the scan I posted, however it appears to be the same as the setup on my '07 Nighthawk (see new scan) with the exception of the wire colors. On the '83 Nighthawk diagram, the wires are (l - r) R, R/Y, R/G, R/W. On the '07, the R/G and R/W are reversed.