Spark units ' ... on the way out ...'

[Kool_Biker]

I have been reading the above on many occasions to describe the spark units on our CBX's departing this world. So I wonder if and what the tel-tale signs are, if any.
With my 79', I am experiencing an annoying 'pinging like' misfire on even light acceleration from 2,000 to about 3,5000 rpm:
It is not always there, never when the bike is cold, and by now I am convinced it is not due to fuel quality, ignition timing & advance springs or wiring of the ignition unit.
From previous experience, this is (one of) the RPM range where it is the hardest for the plugs to fire ...
The pick up and HT coils look good too.

DSC02846_1 (1).jpg

As I do not have a spare unit to swap, and before I splash good money to buy a Dyna unit and, may be, Dyna coils + transport + import duty to Greece , I wonder if there is something I am missing?

Thanks a lot
Aris

[EMS]

I have been reading the above on many occasions to describe the spark units on our CBX's departing this world. So I wonder if and what the tel-tale signs are, if any.
Thanks a lot
Aris

This is hard to say, Aris. The early units are prone to leak and ooze a black sticky fluid. Later (Prolink and CB-F units) are improved and do not leak. They can be identified by the red shrink wrap around the wires.
The leaking, however, is not necessarily a sure indication of the spark units being bad. I have seen spark units with black ooze all over and they were still good and I have seen some that hardly leaked (after 30 years, though, these are really rare) and they were bad.

[Kool_Biker]

Thanks Mike

I guess my question was: do they just go out (as surely some will do), or in some cases their performance degrades gradually.
I had a look at the Honda provided ignitor circuit diagram. My book is for the Z&A models - not sure how accurate it is or if the ignitors were improved at a later time for the B & C models.
Well, I can see a number of components whose specs could change overtime, e.g the 3 capacitors and zener diode. But other parts could also be affected. Who's to tell ..

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Aris

[Goss]

Hello Aris,

Could you not borrow a set locally to eliminate your units? If the problem is only when the bike is hot it may be worth spraying them with aerosol coolant (electronics industry) to bring the temperature on the units down when you experience the misfire to see if it is a temperature related failure.

Good luck and let us know how you get on.

Regards

Goss

[Kool_Biker]

If the problem is only when the bike is hot it may be worth spraying them with aerosol coolant (electronics industry) to bring the temperature on the units down when you experience the misfire to see if it is a temperature related failure.
Goss

Good thinking Goss, thanks, and easy enough to try ... and since you asked, I only wish I could swap the ignitor assy ... not many CBXs in Greece

Aris

[Larry Zimmer]

Any chance one of the carbs is running a bit lean on the pilot/low speed jets? Reasons: loose debris in float bowl, pilot screw in just a wee-bit much, or who-knows-what? I would expect more issue at higher load if ignition were a problem.

[Kool_Biker]

Larry:
All 6 pilot screws are set at the usually recommended, 2.5 turns from closed.
You say might be worth undoing them by ~1 turn, to richen the slow / transition mixture a bit?
Thanks, Aris

[Larry Zimmer]

I would not open them any further. That should be more than rich enough. As I think more about it, could be ignition that is only noticeable under very light load. (Even though there may be some loss at heavier load.) Given everything I've seen in your postings, I'm do expect that you've covered all the usual. Do try the 'cooling' thing with electronic cleaner fluid as mentioned above. Also, be certain to have a good film of dielectric grease under the units when mounted to maximize heat transfer to the mount.

Beyond that, we'll hope that Dave or Mike read this; and, have some better suggestions!

[Kool_Biker]

Hi,

As I am slowly but surely drawn into replacing my standard ageing 79 ignition system with a more modern one, I wonder:
Is there one that also does away with the antiquated mechanical 'bob weight and springs' advance mechanism?

I did the same research only recently for my 72 750 Commando, and NONE of the systems which are available today (and they are quite a few) retains the original crude mechanical advancer of this iconic bike. Can't be that hard!

Thanks
Aris

[Don]

Be V E R Y careful there, Aris - You're sticking your toe in that intoxicating 'let's improve things' door!

First a better ignition system, then you'll want a better set of shocks, then a better set of forks and then a wheel which will fit a real tire and then a set of real brakes to slow it down - Next thing you know, you're on your way to building a great rider

For what little it's worth, in my opinion, all of the above are much more needed than the ignition modification - The stock Honda ignition isn't that bad as it is . . . . when it's working correctly. I would just buy another set of pulsers and play around with those to see if changing one or more makes your miss go away - If it doesn't, you probably don't have an actual ignition problem

Don

[EMS]

The igniters are indeed the weakest link in the 79/80 ignition system and worth replacing. Even just the Prolink ones are better (more reliable)

[Kool_Biker]

Thank you Don, you must be speaking from experience, and I am definitely not planning to go down the slippery slope BUT:

- Since I am to buy ignitors to swap, to hopefully fix my ignition system, WHY go for the original 35 year old (?) design, which will not even save me money on the first place?
- After all, of all improvements mentioned above, this is the ONLY ONE which does not detract from the original looks of the bike.
- And I hear only positive things about the Dyna S ignitors, etc. etc.

I am all for originality and have no aspirations to change my very standard CBX.
But as an electronics engineer, I know that ignition circuits represent an area which during all these years has improved, literally by leaps and bounds.

So, any one out there who knows of a proven system which also gets rid of the mechanical advance? Otherwise I think it will be a Dyna S ...

Thanks
Aris

[Larry Zimmer]

Aris, my thoughts are, that if you are not trying to be ORIGINAL, the Dyna would be the thing to do. I have installed a Dyna on my Suzuki GS750 --- only way to go! (I realize that it replaced the old contact breaker points; BUT, it is direct and eliminates the ignition units. Anytime a component can be eliminated, failure potential is reduced. At the first 'hint' of trouble with my '82, I will install a Dyna.

[Kool_Biker]

Anyone, with any experience on the Probe Engineering ignition system for the CBX?
http://www.probe-eng.com/servlet/the-10 ... ion/Detail
They seem to do away with the mechanical advancer ...
Cheers, Aris

[Larry Zimmer]

Don't know anything about them, Aris. BUT, certainly, sounds goood! Several unique worthy features in their system that would make it worth the extra $100 over the Dyna. (Tach output, coil current averaging, electronic advance.)