Topic: Bolt on HiPo Coil and H/T wires

[timtune]

Is there any aftermarket coils and H/T wire kits that are a direct bolt on for my 76 CB750F?

Thanks

[Bodi]

I have never seen one. The Dyna coils are pretty close, I think you have to file off a small lug on the OEM mounts but they then bolt right on. The Dyna cables come with 2 lengths each with coil caps on both ends, you cut them to length for two plugs and then add your new plug caps (purchased separately or reuse your old ones).

[HondaMan]

Go look at PartsNmore, CB750K electrical section, Sakura coils #17-6823. They are a drop-in for the CB750 and work perfectly.

[timtune]

Thanks HM. Any idea how hard it is to replace the H/t leads? I know there is no really good reason but I want the yellow leads. Isn't yellow the fastest colour?

[HondaMan]

The

Thanks HM. Any idea how hard it is to replace the H/t leads? I know there is no really good reason but I want the yellow leads. Isn't yellow the fastest colour?

spark leads on these coils are molded into the coils themselves, not removeable. This is done to prevent moisture ingress that slowly damages the spot-weld where the wire is joined to the coil windings, just inside the coil body. Then the coil's body mold is made over the joint to protect it.

For a while (don't know if they are still around?) there were some ACCEL brand coils that could (barely) fit under the gas tank, which had separate wires. Trouble is, they are 3 ohm coils, which your bike (or any SOHC4 bike) cannot feed: that's too low resistance, and it causes overloading of the charging system and a constantly-flat battery. There's no magic battery that can 'fix' this, only load reduction to meet the 90W of the 500/550 or 140w of the 750 alternator's ability to generate. Honda's alternator maker in those days (Hitachi and TEC) didn't make very powerful bike alternators. Most modern bikes have to deal with onboard electronics, fuel injectors, high-power headlights, etc., etc., so most bikes made after about 1980 have alternators almost twice as powerful (or more) as ours. So, don't get too crazy with add-on electrics, or you'll likely get so frustrated with its constantly-low battery that you will sell the bike: I have seen this MANY times.

[timtune]

So there is no easy way to get the yellow H/T leads I'm craving? It's one small feature that stands out and in my mind looks good.

[Deltarider]

That 3Ω coils draw too much current is a myth, I'd like to bust once more. I have been riding my CB500 with 55/60 Watts H4 and 3Ω Dyna coils for decades now and after every ride I return with a better charged battery than I took of with. It seems that so far I'm the only one that did a simple measurement instead of reciting Ohm's law over and over again. http://forums.sohc4.net/index.php/topic,175144.msg2038035.html#msg2038035 Anyone can do this measurement. Please do and prove me wrong! I beg you. 
What's causing the socalled charging issues in the US (and only there!) is:
a) silly gadget show lights which do nothing but waste an extra 16 watts.
b) silly headlamp-always-on-wiring that depletes your battery already before you're on your way, even more after you did some maintenance with IGN in ON. This was NOT Honda's idea.
c) Too many stops (US infrastructure with STOP signs everywhere) and too low rpms.

[bryanj]

Delta, yes it is a bigger problem in US BUT that is where both Hondaman and TT live so no matter what you think they are giving good and true advice, i also know from workshop experience that it CAN be a problem in UK, if fact simply fitting an H4 CAN cause problems but not always, we have lots of corners and slow roads here

[goodtryer]

That 3Ω coils draw too much current is a myth, I'd like to bust once more. I have been riding my CB500 with 55/60 Watts H4 and 3Ω Dyna coils for decades now and after every ride I return with a better charged battery than I took of with. It seems that so far I'm the only one that did a simple measurement instead of simply applying Ohm's law over and over again. http://forums.sohc4.net/index.php/topic,175144.msg2038035.html#msg2038035 Anyone can do this measurement. Please do and prove me wrong! I beg you. 
What's causing the socalled charging issues in the US (and only there!) is:
a) silly gadget show lights which do nothing but waste an extra 16 watts.
b) silly headlamp-always-on-wiring that depletes your battery already before you're on your way, even more after you did some maintenance with IGN in ON. This was NOT Honda's idea.
c) Too many stops (US infrastructure with STOP signs everywhere) and too low rpms.

You say the charging issues are a myth and then provide 2 specific causes of the mythical behavior, both of which are beyond our control. The silly headlamp is on by law; it's not up to us. The silly stop signs are also law. To reach your non-US nirvana here, should we re-wire the headlights and cut down the signs?

[Bankerdanny]

The

Thanks HM. Any idea how hard it is to replace the H/t leads? I know there is no really good reason but I want the yellow leads. Isn't yellow the fastest colour?

spark leads on these coils are molded into the coils themselves, not removeable. This is done to prevent moisture ingress that slowly damages the spot-weld where the wire is joined to the coil windings, just inside the coil body. Then the coil's body mold is made over the joint to protect it.

For a while (don't know if they are still around?) there were some ACCEL brand coils that could (barely) fit under the gas tank, which had separate wires. Trouble is, they are 3 ohm coils, which your bike (or any SOHC4 bike) cannot feed: that's too low resistance, and it causes overloading of the charging system and a constantly-flat battery. There's no magic battery that can 'fix' this, only load reduction to meet the 90W of the 500/550 or 140w of the 750 alternator's ability to generate. Honda's alternator maker in those days (Hitachi and TEC) didn't make very powerful bike alternators. Most modern bikes have to deal with onboard electronics, fuel injectors, high-power headlights, etc., etc., so most bikes made after about 1980 have alternators almost twice as powerful (or more) as ours. So, don't get too crazy with add-on electrics, or you'll likely get so frustrated with its constantly-low battery that you will sell the bike: I have seen this MANY times.

I have a set of the Accel coils that I got with the roller F3 that provided the front end on my F1. I tried many different ways and simply could not find a way to mount the coils on my bike. They (and the Hondaman resistor setup I bought from you) are just sitting in a box of spares.

[Deltarider]

Delta, yes it is a bigger problem in US BUT that is where both Hondaman and TT live so no matter what you think they are giving good and true advice, i also know from workshop experience that it CAN be a problem in UK, if fact simply fitting an H4 CAN cause problems but not always, we have lots of corners and slow roads here

The myth started here in this forum, Bryanj. Find me another forum where 'the problem' was discussed before it started here. Good lord, some models CB500/550 for the European continent came even standard with a 55/60 Watts H4. None of the fellow CB500/550 owners I know, ever had a problem with the charging. In my archives I have several riders' reports in which, I don't know how many owners of CB500/550s have shared their long time experience (in distance over 40 times around the globe). I find it telling that criticism on the charging system is totally absent in all of them, tests as well as reports. Find me American tests, magazines, what ever, where 'the problem' was recognised, before it was here. In several posts I have given advice to deal with he specific US situation. I have no idea how many have fit that relay.
Sometimes I wonder if some here are really only interested in giving 'good and true advice', Bryan, or are also interested in profiling themselves as expert. Look, I am honest enough to say I am an amateur, so, please, do the ampère test, both with stock and with 3Ω coils. Hey, what opportunity to show that I am 'dead wrong'!. My goodness, it's about time to stop this repetitive nonsense.
Let's end this with this joyful vid. Just imagine the problems them poor cops must have had back then. :

[Rookster]

NGK makes spark plug wire splice kits that work well.  You can keep the stock coils and splice new wires or you can get the replacement coils Hondaman mentioned and splice new yellow wires on. 

https://www.summitracing.com/parts/ngk-8083?seid=srese1&gclid=Cj0KCQiAip-PBhDVARIsAPP2xc07gPDO5AaTvBYZqZl1UVjWagst_gP3LZ15qJKIE3NM-fYNWGE66aYaAiQkEALw_wcB

Scott

[PeWe]

3ohm coils drained my CB750 battery very quick together with Dyna-S ignition.

Back after a 50 km test ride I had to start it again to park it in the garage. Starter barely made it.  Half of the distance with headlight off.

Country roads only, min speed 70kmh, mostly 100 kmh. Rpm mostly over 4000 rpm.

I went back to shop and could get the Dyna 5ohm version instead. After that no problem.

So why use 3 ohm coils?
Dyna 2000 is designed for it, must have,  but for Dyna-S or stock points not needed.

I think it is a myth that 3ohm coils make engine to run better.

[scottly]

So there is no easy way to get the yellow H/T leads I'm craving? It's one small feature that stands out and in my mind looks good.

Get some yellow heat-shrink tubing and fit it over the stock HT leads.

[PeWe]

If using Dyna coils, use the stiffer copper leads. Soft and pliable will glide out from the coil connection rather easy, especially 1 or 4.  Happened me several times.

H/T lead can be bought by foot or meter.

[Deltarider]

3ohm coils drained my CB750 battery very quick together with Dyna-S ignition.
So why use 3 ohm coils?
Dyna 2000 is designed for it, must have,  but for Dyna-S or stock points not needed.
I think it is a myth that 3ohm coils make engine to run better.

Yes, I've learned that. In the 80s I myself fell victim of it. I really believed there was something extra to gain by applying 3Ω coils. Not so. But it is also a myth that 3Ω coils draw a lot more current. They don't, at least not in my measurement. So I suppose the Dyna EI, being a generic product, is the real culprit, probably offering an extended dwell time you don't need, not on our bikes.
For a good understanding we should make a distinction in observing things static and dynamically, because there's more at play than simply deducting Watts by applying Ohm's law.
The best instructive vids about our SOHC Fours are made by Marco, a member of the German forum. With his soft, modest voice he demonstrates restaurations in detail, explains all his findings, etc. Although it's in German, I like to honour him and present a link to his tutorial on the CB350F ignition system which is ofcourse very similar to ours. Although the video is worth watching as a whole, I'd like to point at the section where he summarizes all data on paper: 26:52 - 35:26 and - more in particular - where it is about Sättigung (saturation) in 28:41 - 29:12. Man, I had never heard of 'tau' (expressed in the symbol τ) before. Also new to me was, that there's a standard formula for inductance and that at max rpm in Honda's stock set up, our coils become saturated for only two thirds. Actually partial saturation begins already at around 6500 rpm. TEC has ofcourse dimensioned the coils thus, that they are adequate. But you will now understand that manufacturers of aftermarket ignitions rush to the scene and characterise this partial saturation as a shortcoming. They can offer - and here's the magic word - more. And more goes down real well in a market. where consumers are already primed to interpret quantity as quality. I also was a victim of that,
For convenience I've made a copy in translation, which you find below. If you need more translation, feel free to ask. If you can shoot holes in his explanation, you're invited ofcourse. He is a friendly person and always open to criticism.

HONDA CB350F  IGNITION                          Specifications and Settings
         COILS                                                            TEC FL703-12V
  Primary resistance                                                     ~ 4,5Ω
  Secundary resistance                                                 ~ 14,7kΩ
  Turns primary                                                               420
  Turns secundary                                                         13.000
  Voltage secundary                                         @ 1000¹/~14kV  @10.000¹/~11kV
  Inductance                                                                ~ 14mH 
  Saturation (see 28:41-29:12 for explanation)   τ  = L/Rp = 3,1ms (63,2%)   τ  x 3 = 9,3ms
  Charge time @   1.000 rpm and 55% Dwell*     1 revolution = 0,06s         >        33ms
  Charge time @ 10.000rpm and 55% Dwell*      1 revolution = 0,006s       >          3,3ms

       CONDENSERS
  Capacity                  0,22 μF +/- 10%

courtesy Gruzzel

* Actually it is 55% Duty Cycle which equals 49,5^o Dwell (4 cyl scale) which is a tad narrower than a 0,3 mm gap. Personally I'd chose a somewhat wider opening as the gap tends to narrow over time (Deltarider).

[PeWe]

Pamco Pete had similar descriptions for his ignition using 3 ohm coils (maybe even 2.8?) but still not drain the battery.

[Bodi]

So your bike is perfect, meaning that the electrical problems are a fantasy - the rest of us are imagining that our batteries are usually barely charged and electric start is unreliable?
And what does coil saturation have to do with anything? I don't think the stock coils are a problem. I used Dyna coils because the original molded in cables had deteriorated.

[rotortiller]

Deltarider, I agree instead of 'nut-swinging' people should go and measure electrical parameters. Anything over 1800 rpm with the 50/60 watt headlight on and my bike supplies over 14volts thus powering everything from the alternator. I have found that installing a fresh AGM battery lowers the rpm where the system pumps out 14+ volts, basically due to a more efficient performing battery. After this RPM point my battery is just going along for the ride as the alternator is the power supply, energizing the ignition, lighting circuits and providing battery maintenance energy. The guys with problems should look into the bikes electrical systems for  problems.  I have had dated wet pb batteries that appeared to hold a charge go somewhat dead on a city ride which actually started the bike fine with the electric starter when I left. There is not  a large head room in the alternator as we all know so when components are not ideal #$%* will happen. BTW I use stock reg/rectifier set to  clip at 14.5 volts maximum. The way I see it is a person can correct a problem or mask it by reducing the electrical demand (LEDs). Alternately adding too much extra electrical load (high dwell etc) may break the camel's back. Using a multi meter and measuring will tell you if you have gone too far with alterations. They were not electrically stupid when they designed the bike, unlike some of us lol (been there bought the shirt).
 

[eldar]

I think what we need to know is the max wattage that can be supplied by the 500/550 alternator. It's not just a voltage game. You can have 14.5 volts, but have barely any wattage that is actually charging the battery.
So, what is the max wattage, as stated from honda? Once we have that, we can then draw a decent picture of the true charging capacity once everything is factored in.

[RAFster122s]

Read HondaMan's post above ...he answers your question
Then you can go add up all the loaded of lights, coils, rect/regulator, etc...

[Deltarider]

Read HondaMan's post above ...he answers your question
Then you can go add up all the loaded of lights, coils, rect/regulator, etc...

And what if one miscalculates the coils demand? What if one presents alternator outputs too low?

[Deltarider]

I think what we need to know is the max wattage that can be supplied by the 500/550 alternator. It's not just a voltage game. You can have 14.5 volts, but have barely any wattage that is actually charging the battery.
So, what is the max wattage, as stated from honda? Once we have that, we can then draw a decent picture of the true charging capacity once everything is factored in.

Eldar, you're to the point. In the Shop Manual Honda CB500-550, on p.136 Technical data CB500, we find a healthy 0,2kW @ 5.000 rpm. Problem is that US riders never go there. They concentrate on p.171 instead, where they read 0,13kW @... 2.000 rpm.

[Don R]

 I'm guilty of lugging my engines too. My 76F would always tell me if I wasn't riding enough at rpms,  in town, short rides etc. the turn signal beeper would get feeble. L0L!  I'd put it on the maintainer or take it for a nice long ride.

[PeWe]

Cruising around in legal speeds on cozy country roads will happen at less than 4000 rpm on a CB750.

So a voltmeter placed between the gauges is a good help to see when time to ride faster or gear down

Ensure that all connectors everywhere have a tight clean fit another thing. Good grounds included.

Use a Honda right hand switch with Off- Parking-Headlamp, Hi-Lo on left side helps when time to reduce load.
A LED 10W parking bulb will make bike visible at daylight where the law is light on.

My K2  RHS has only Off, Lo, Hi for the moment. But can help daytime if needed.
Aftermarket switch from 4-1.