Starting problem, no spark

[geisterfahrer]

Not my GS750L, which is running fine, thanks in part to the wonderful people on this forum. It's my '83 Nighthawk 650. Similar vintage, and similar technology.

It started and ran great first thing this spring. Then it started getting hard to start with the starter motor. Then it got to a point where it could only be bump-started. Once started, it ran great. Now it won't start at all. No fire to the plugs.

I have checked the pickups, coils, and plug wires. All are within spec. The battery is new, and kept charged with a trickler. I have double-triple-quadruple checked the kill switch and clutch switch. I have replaced the ignitor unit (with a used one, of course, so no guarantees there).

I'm running out of ideas, and I hope someone here can help. What am I missing, that would cause the bike to gradually stop running?

Sorry it's not a GS-specific query, but I've found the group here to be very knowledgable and far more active than the few Nighthawk-specific groups I've found.

Thanks!

[Guest]

With the new battery you have the starter turning?

[geisterfahrer]

Yes, the starter works fine. The engine turns over easily, and everything sounds just like it did when the bike ran. Just no fire.

[rustybronco]

do you have a wiring diagram and do you have voltage at the coils?

I work in romeo.

[geisterfahrer]

Dale,

I do have a wiring diagram in my Clymer manual. I'll check tomorrow about the voltage at the coils.

I work in Almont (most days, anyway )

Kevin

[rustybronco]

Don't know those bikes... will normally crank and not fire when the side stand is up, or it won't crank at all with it up ?

Might have be a road trip involved

[geisterfahrer]

The '83 Nighthawk did not have the sidestand interlock. My '07 does . I wish it were so simple!

[rustybronco]

'83 cb650sc? if that is correct, what I have read it has it. you would know better than what I found.
but as you say they work pretty much the same, shouldn't be to much of a problem to get it up and running.

possible to scan and post the diagram so I/we may peruse it?

[Smokinapankake]

Getting fuel? Only have to have three things for ignition: Fuel, air, and spark. Got all 3 there's no way it won't fire.

[geisterfahrer]

Definitely getting fuel and air. This spring, once the engine would start, the bike would run like a scalded dog. It just slowly became harder and harder to start.

I have tested for spark by plugging a known good spark plug into the boots, and grounding against the engine. No fire. I have confirmed the presence of fuel in the carbs, plus I can smell gas from the exhaust after cranking. I don't think it is a fuel issue. I suppose there could be an air problem, if the intakes were leaking, but wouldn't that cause the engine to run poorly once started?

[almarconi]

If you had an intake leak the bike should start..would run like crap but would start.

Did you check to see if you have voltage at the coils? Check the primary and secondary resistance of the coils, as well as, resistance of the caps.
Check the wires going to your black box to make sure all connectors are clean and tight. Not sure exactly how you can test your ignitor but if you have a spare it might not be a bad idea to swap it out and see if you have spark.

Its been my experience that most electronic/computers in bikes and cars usually will fail spectacularly. Meaning they either work or they dont. They usually don't degrade over time. Corrosion which occurs over time could cause your electrical system to have problems. Did you check all your ground points to make sure all is tight and clean?

[geisterfahrer]

possible to scan and post the diagram so I/we may peruse it?

Here it is...

[geisterfahrer]

And page two (Do I hear Paul Harvey?)

[Steve]

Getting fuel? Only have to have three things for ignition: Fuel, air, and spark. Got all 3 there's no way it won't fire.

Just a little modification here.

Yes, there are three things needed, but the fuel and air become one item as a mixture.
The other two items are spark and compression.

.

[geisterfahrer]

[quote=almarconi;884671Did you check all your ground points to make sure all is tight and clean?[/quote]

I'm inclined to agree with you on the failure mode of CDI ignitions. There has to be something that has progressed over time that has caused this problem. I have not had time to strip the bike down and check every ground point. I'm planning on doing that over the long holiday weekend, unless I decide I'd rather ride somewhere . I have a little time today, and I may start poking around.