Topic: CB650 Ignition

[Pinhead]

Both of my coils are cracked so I'll have to eventually replace them; I'll upgrade plugs and plug wires at the same time. My "spark boxes" are melted, so they'll eventually have to be replaced, too.

Can someone please explain to me, in detail, the workings of the '79 and up CB650 electronic ignition? What exactly do the two "spark boxes" do (and why do they each have 5 wires?)? How exactly are they triggered? How does this translate to the coils? What can I "upgrade" to without spending a fortune (stronger coils or spark boxes from another bike?)? I know the 650's ignition is leaps and bounds above the '70s stuff, but surely there's been upgrades made by Honda during the '80s that I could easily adapt to my bike...

[nickjtc]

All righty then...here's the griff from the Honda workshop manual I have for my '79 650.

"A TRANSISTORISED IGNITION SYSTEM is used and no adjustments are made unless the pulser generator screws are loosened. If these screws are loosened ignition timing for either the No.1 or No.4 cylinder must be adjusted.

The ignition system has two sub-systems: one for the No.1 and No.4 cylinders and one for No.2 and No.3 cylinders.

Ignition timing: at idle speed 10 degrees before top dead centre
                     at full advance 28.5 degrees before tdc (2725rpm)"

Under the right hand engine side cover is an electronic 'pulser' generator with two pick-ups, and inside that (towards the centre of the engine) is a mechanical spark advancer. So the pulser generator picks up the signal from the rotating spark advancer which is sent to the appropriate spark unit (above and adjacent to the battery), which in turn signals the coils to do their thing.

I cannot comment on the long term reliability of this system, but would have to assume that it was the best Honda could do at the time. I've had no problems with mine in the 9,000+km I have had the bike. However, because it relies heavily on electrickery I can imagine that there is a recipe for disaster if the pulser generator or the spark unit goes on the fritz. As to 'modern' options, I'll throw that out to more knowledgable members of the forum. I suspect that the OEM system is as good as it gets....but maybe Boyer makes a more modern alternative. Can't see anything here:

http://www.boyerbransden.com/html/honda.html

Anyhoo: The five wires coming out of the spark units are: yellow, green, black/white, blue and white.

They pass through two white mini connectors. From one connector the emerging wires are, respectively, blue, green, black/white, and two more blue wires. Blue to coil, green to ground, black/white to the starter switch on the 'bars, and the other two blues to the pulser pick-up, via another white mini connector.

From the other connector: yellow, green, black/white, and two more yellows. Yelllow to coil, green to ground, black/white to join the other black/white to the 'bars, and the final two yellows to the other pulser pick-up via the mini connector.

Clear as mud?? If you have access to a fax I'll copy the pages and send them to you. Sorry, I lack the technology to scan etc...!!

[Pinhead]

I'm going to have to compare that to my bike so I can "see it" to learn how it works.

I know the '79 to '83 CB 650/750/1000/1100 use the same ignition system. I don't know if the coils on the bigger bikes are more powerful or not. That'd probably one good upgrade... I think the spark boxes are identical, though. I'm going to look for some '83 stuff to see if it'd be an upgrade.

[Soos]

I kow coils off a '79DOHCcb750 work fine with the '79cb650, in fact they are the identical part #.
I have a '79750DOHC i bought for the dual disk front end for $50, and have tried all the electronics I can so far, and all work.
The advancer mechanism seems a bit(but not too much)different.
the CDI units are a drop in part(same part #'s).

As for as a upgrade, Dyna DC1-1 are a drop in replacment.
No fabricating of a custom mount either.
One side(the left?) is REALLY close, but they fit.
I would say a DEFINATELY boost in spark though.
For $120, not too bad, considering replacing with aftermarket OEM style is about 60+.

l8r