Topic: CB500 Replacement Coils

[igraul]

Friends, I swear I searched first. I'm just looking to find out what modern options are available to replace my coils. I have a Clymer manual, but I can't find sufficient coil specifications to know what I should be looking for. I sincerely appreciate any knowledge/experience you can share.

Cheers!

[Bodi]

You want 5 ohm dual fire coils. Dyna has ones that fit with minor mods to the stock mounts. Get their cables as well but you can make your own. Don't know the part # now but it's easy to find.

[bryanj]

Why, theres nowt wrong with Honda ones, you wont get a better spark from pattern ones

[HondaMan]

You can also use the Sakura brand coils from PartsNmore. Find them in the CB750K section. Same size, same wiring, have used them several times (even on my own bike).

[Deltarider]

My approach is, that I don't replace any part before I have diagnosed what is wrong.
Be aware that some aftermarket coils might have their primary connectors 'gender' wrong.
For a good working ignition good and firm contacts are essential. It's well possible that someone attributes improvement to a new part he or she has fitted, while in reality the connection was redone and now as it should have been before.
Here are a few connections which deserve attention:
HT lead - plugcap (you may also check the caps resistance). Realise that the plugcaps are the CB500/550's Achilles heel.
The Y connector primary side where the Bk/W wire devides in two.
Contactbreakers: the little bolt in the breaker must be securely fastened to prevent a wandering dwell
                          make sure the breaker's connectors do not ground intermittently.
Having run OEM and 3Ω coils, I for myself can conclude that the primary resistance doesn't matter  much, as long as it is in between 3 and 5Ω.
I have not been lucky with R(esistor) spark plugs.

[HondaMan]

I have not been lucky with R(esistor) spark plugs.

Delta: what kind of troubles have you had with the resistor plugs?

[Deltarider]

They may perform well on CB550K3s and K4s which models burn leaner. On mine they sooted more and - rarely - can stop functioning out of the blue (2X). It's one of the reasons I have stopped using Dynatek plug wires and caps as these aftermarket products forced me to use R plugs. I'm back to NGK plugcaps with inbuilt resistors. Also I didn't like Dyna and Dynatek as far as connecting. They look solid, but they are not, not on my bike. Shielded under the hood of a car they may perform fine, not in the riding wind.
Also I noted that for some reason the Denso R plugs' resistance increased over time (all 4) and the NGKs (all 4) decreased. But... I hesitate to communicate this, as that's just what I have witnessed, so it's hardly scientific and neither do I have an explanation for it.

[HondaMan]

They may perform well on CB550K3s and K4s which models burn leaner. On mine they sooted more and - rarely - can stop functioning out of the blue (2X). It's one of the reasons I have stopped using Dynatek plug wires and caps as these aftermarket products forced me to use R plugs. I'm back to NGK plugcaps with inbuilt resistors. Also I didn't like Dyna and Dynatek as far as connecting. They look solid, but they are not, not on my bike. Shielded under the hood of a car they may perform fine, not in the riding wind.
Also I noted that for some reason the Denso R plugs' resistance increased over time (all 4) and the NGKs (all 4) decreased. But... I hesitate to communicate this, as that's just what I have witnessed, so it's hardly scientific and neither do I have an explanation for it.

I've had some strange experience with the new (made in China) Denso R plugs, too. I've used the NGK R plugs DR8ES-L a few times with no issues when I've had to ride a lot in-town with no hiway speeds, and they stay a cleaner for longer (with the resistor plug caps, on Sakura coils). But when trying the Denso version, they would not idle well after a few of days of city stop-and-go traffic. Switching to the regular Denso plug X24ES-U works better than any other on the hiway in my bike, though, with smoother high speeds and better gas mileage, plus a cooler-running engine (750). I've also had good luck with the X22ES-U plugs in the 550 engines I've rebuilt, but I don't get to ride them very far.

[Deltarider]

I am not 100% sure the built in resistor was the culprit in my particular case, as at the same time I discovered irregularities with the connections. These Fours are so forgiving, that you easily miss an intemittent misfire, where a two cyl. bike will let you know rightaway. I then remembered having read in the past two workshops, including Honda4.nl, who is specialized in our bikes, advised to abstain from R plugs. When a CB Four builder in England reported he had cured quite a few bad running CB Fours, by just replacing these plugs by standard, I decided to do the change in one go, which - I must admit - is not very scientific. My gut feeling is the R plugs may be very reliable in more modern bikes which burn way leaner than ours. Also, a lot of the members here, are doing maintenance themselves and I have the feeling there's quite a lot of idling going on while doing that.

[HondaMan]

Hmm...this makes me think that this coming winter will see me back on my electronics bench, testing these plugs to see what's up. I have an idea what may be the issue, based on what happened with the once-great Champion sparkplug label when China bought it some 15 years ago. In those plugs, the resistor caplet (it's a compressed carbon rod held inside the upper insulator by 2 contacts) was formerly held in place with tungsten contacts so they would never burn nor tarnish. The Chinese makers changed them to some other [cheap, I am sure] metal, and suddenly 3 of the 5 plugs new Champion plugs I put in my V-8 engine of my car didn't work, right from the new box. I cut them in half lengthwise to see what was inside and found the cause: then I bought some Autolite resistor plugs that worked better. I suspect that since now the new Denso label says "Designed in Japan, made in China" then the same sort of cheapening has happened.

The contacts between carbon resistors like these and high-EMF conductors like the guts of these plugs and their exposed tips MUST be impervious to arcing, and the only way that can happen is with extreme purity of materials: tungsten, gold, and a couple of space-age materials are the only things that can do it for very long. I am also convinced that the reason a Chinese-made tungsten-filament lamp burns out quickly is due to the highly impure quality of the tungsten filaments: I had to study those sorts of failures in a couple of my previous jobs. Pure tungsten only comes from 2 places on this planet, and neither one is in China.

[Deltarider]

Nowadays Dutch companies are very cautious when making deals with Chinese subcontractors. They learned. More than often Chinese enterpreneurs at first made products perfectly corresponding to the specifications the Dutch clients demanded. After a year or so, batches would arrive with the products which, although looking identical, were no longer in compliance with the original specifications. Gambling is rampant in China.