1982 cb900f resurrection NO SPARK???

[alero29]

Well jumpered the ignition switch and no go.  Same spark issue (only tiny spark when letting off starter).  I guess I need to start from the beginning (again) and try tracing it all the way through the system...

[TOOLS1]

It seems like it is only charging the coils when the starter is cranking the engine over, and then stopping when the starter button is released, but you say you have voltage at the coils. Check the switch.
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[alero29]

Yes voltage at coils when key is on.  I assume you are referring to the 'kill' switch TOOLS?

[TOOLS1]

No, the starter button circuit. But since you have voltage at the coils all the time, I am thinking the CDI has a problem.
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[alero29]

This has the two spark units (that I believe make up the "CDI").  It seems unusual to me that both of these would fail and I would have zero spark on all cylinders.  If I had spark on two and none on the other it would seem like it would make more sense.  

I did start to try and troubleshoot the spark units per the manual, however was having trouble understanding what wires/connectors needed to be grounded and voltage tested.  Plus I was second guessing if the procedure was the same for and '81 CB900C as that is the manual I have printed.

I have started trying to simplify the wiring diagram down to just the starting circuit and get rid of all the other 'stuff' so I can focus on the key items.  I wish I had a running bike or new someone who had one that I could test some of my components on as this seems like a moderately simple starting system....

Thanks for pondering this!  It's always nice to bounce ideas off of others.

[TOOLS1]

The ignition sysyem is the same on all the DOHC engines. 750-1100.
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[motogrady]

Weak battery.  

[alero29]

I don't believe it is a weak battery.  I have tried this with a fully charged battery as well as a partially drained battery and no difference.  Lately I have been connecting jumper cables from my wifes Durango direct to the moto battery and cranking that way, so there should be sufficient juice!  

Maybe its worth trying a different/bigger battery.  I would be stoked if that resolved the issue, but upset that I bought a $170 battery and custom fit it under the gas tank only to find out it wasn't going to work...

[motogrady]

alero29 wrote

I don't believe it is a weak battery.  I have tried this with a fully charged battery as well as a partially drained battery and no difference.  Lately I have been connecting jumper cables from my wifes Durango direct to the moto battery and cranking that way, so there should be sufficient juice!  

Maybe its worth trying a different/bigger battery.  I would be stoked if that resolved the issue, but upset that I bought a $170 battery and custom fit it under the gas tank only to find out it wasn't going to work...

Ya, I agree.   Jumping a car battery to it should do it.  I suggested that because a weak battery just really messes with mine.  In a few ways.   Gotta be something else then.  

How about using a timing light?  Work from the plugs back to the coils.  Where it stops flashing when cranking should be where the issue is.  Unless it's a dead short, bad switch, or weak connection somewhere.
Maybe get a set of alligator clips and make up a jumper wire.  Start jumping past everything on the handlebars.  Disconnect all that stuff, something might be grounding it out.  One would think you could jump right from the battery to the coils, then jump the starter with another wire.
Electrics, you gotta love em.

You find it let us know guy.  

[motogrady]

Hey guy, my 79 is running, and I have an 82 that is pretty much unmolested.
U need a few pics of how stuff is wired up let me know.  I can send u some pics of mine if it helps.  [e-mail]

[alero29]

Motogrady - I appreciate it, I will likely reach out!  I need to find some time to dig into this again and try a few more things. If you see an email from wecks13@hotmail come through it isn't spam!