Topic: cb550 dyna ignition query

[rosewood]

Hi All,

I have a question regarding converting a CB550 to electronic ignition (Dyna s and dyna coils)..

Currently trying to restore and bring to life an old cb550f, I have a number of issues (mainly carburetor) but my attention at the moment is the ignition system. The PO installed 3ohm Dyna coils with the original ignition system.

I have had problems running the bike especially when the battery begins to drain, difficulty starting and maintain running. I have a suspicion that the 3ohm coils are drawing too much current than the alternator/charging system can safely handle.

I have tried reverting back to the original coils which seemed to work but they are in a very bad state. One of the spark plug cables was damaged and cut short so I had to splice a new section onto the end of it. The insulation is cracked and damaged especially at the coil casing and being so old I don't have a lot of confidence in them.

My question is if I purchase a Dyna S ignition system can I run the bike safely with the 3ohm dyna coils I already have or would this still put too much load on the bike alternator?

I like the idea of the Dyna ignition but I have a budget, so the option at this stage is 5ohm dyna coils with the dyna s ignition or 3ohm dyna coils with stock ignition.

which would be better or work well on an otherwise stock bike? the exhaust system is standard but I will mostly likely be running pods on the carb (which i know will cause all sorts of tuning problems).

Thanks
rosewood 

[flatlander]

if you're on a budget, why not get OEM coils or 5 ohm coils and keep the points?
there's a thread with lots of info about coils here: http://forums.sohc4.net/index.php/topic,29545.0.html

[przjohn]

I chalked it up to a learning experience and took the loss on a 400f. Went back to points and the charging system is happy.

[HondaMan]

The 550 cannot support the 3-ohm coils unless you add some more parts first. In order to use them, you would need to add a series resistor with each coil (I make something called a "Resistor Pack" for this). The alternator on the 550 simply is not big enough to feed these current-hungry gadgets.

Similarly, the Dyna S uses 1.2 amps more current than points. The 550 can successfully use the Dyna S IF the headlight is stock or a lesser-wattage H4 unit, and the bike is used more on the hiway than in city traffic, because the charging system will not "catch up" to the extra power loss until the engine is running at 5000 RPM or so.

Using both the Dyna S and the 3-ohm coils will guarantee you will have a very low battery and [sometimes] a fried rectifier, if the alternator survives at all. Search for the Dyna S in the 550 (or the 500/350F/400F) here in the forums, and you will find this story repeated many times.

Using the points with the OEM coils or Dyna's fine 5-ohm coils (or the Sakura coils sold by PartsNmore for the CB750 1970-1978 models) will work very well. If you wish to use the 3-ohm coils (because they have nice plug wires that can be changed), then add some 2-ohm Resistors (or my 2-ohm Resistor Pack) to those coils, to save yourself some nasty headaches!

[Gordon]

The 550 cannot support the 3-ohm coils unless you add some more parts first. In order to use them, you would need to add a series resistor with each coil (I make something called a "Resistor Pack" for this). The alternator on the 550 simply is not big enough to feed these current-hungry gadgets.

Similarly, the Dyna S uses 1.2 amps more current than points. The 550 can successfully use the Dyna S IF the headlight is stock or a lesser-wattage H4 unit, and the bike is used more on the hiway than in city traffic, because the charging system will not "catch up" to the extra power loss until the engine is running at 5000 RPM or so.

Using both the Dyna S and the 3-ohm coils will guarantee you will have a very low battery and [sometimes] a fried rectifier, if the alternator survives at all. Search for the Dyna S in the 550 (or the 500/350F/400F) here in the forums, and you will find this story repeated many times.

Using the points with the OEM coils or Dyna's fine 5-ohm coils (or the Sakura coils sold by PartsNmore for the CB750 1970-1978 models) will work very well. If you wish to use the 3-ohm coils (because they have nice plug wires that can be changed), then add some 2-ohm Resistors (or my 2-ohm Resistor Pack) to those coils, to save yourself some nasty headaches!

This is gospel in the SOHC4 world.  Learn it.  Live it.  Love it. 

Seriously.

[rosewood]

Cheers for all the input...it sounds like this topic has been thrashed before but i just needed some confirmation regarding the 3ohm coils as I've read some conflicting information.

Finding stock/OEM parts in New Zealand for these old bikes is very difficult so its often alot more cost effective buying aftermarket parts off shore and the reason I wanted to keep dyna coils is I like the idea of being able to replace plug cables unlike the stock ones.

Since my points system may be a bit suspect I thought it may be an opportunity to upgrade to electronic and not have to worry about gapping and timing but it sounds like this is not ideal.

Hondaman I will also send you a message but do you ship overseas?

cheers
rosewood

[Deltarider]

Personally I haven't any problems running 3 Ω coils on my CB500 that has the same charging system as the 550, not with the transistor ignition module I had built myself, nor with the original breakerpoints now, since I returned to them after damaging the wires of forsaid module (it still awaits repair ). Although I also run a 55/60 Watts halogen, from every ride I return with a better charged battery than I took off with. I suspect it has to do with the rides you do. Personally I avoid short rides and try to avoid city traffic as much as possible. So in principle the charging system can handle it. If you are in city traffic and at traffic lights often and you roll along on too low rpm (an American habit), you can expect drainage. The running lights wiring on US models that brings on the headlight before you have even started (!) the bike doesn't do much good either.
On my bike when idling I've noticed some voltage drop measured between the battery + and the + side of the coils (close to 2 Volts @ idle). I will do a test later riding (higher rpm) and report on this. So you might say the 39 year old wiring on mine works as a 'natural' resistor. Hondaman's suggestion to mount a 2 Ω resistor is only good as long as there is no further resistance in the wires to the coils. If there is like on mine, I would not go further than an 1 Ω ballast resistor, 1,5 Ω maximum.
Btw, the idea of the 3 Ω socalled 'superbobine' back then was also to make cold starting easier. Therefore during starting the resistor was bypassed to have the full 12 V at the coils. Old Honda Goldwing models have that arrangement. You can study that elegant solution in a wiring scheme of these old Wings and copy it to your bike.
This all goes when you have these 3 Ω coils already. If you have to buy new I would recommend coils that are close to the 4,7 Ω measured on stock coils.
It could be there is an advantage in using 3 Ω coils in combination with a ballast resistor. I have not understood this yet. Maybe Hondaman can shed some light on this.

[rosewood]

Cheers for the input Delta...

I live in Auckland, New Zealand which has very bad traffic congestion problem so city riding and stopping at traffic lights is inevitable even though this bike will be a weekend cruiser.

I measured my cap resistance today which read   4.48, 23, 12.16, and 9.98kOhm from 1-4 cylinders respectively so i think I have some other issues there aswell..

I think my safest bet so far is to get the standard points system running properly (new points and condensors) with either 5ohm coils or Hondaman's resistor pack and the 3ohm coils I currently have..

[Deltarider]

I measured my cap resistance today which read   4.48, 23, 12.16, and 9.98kOhm from 1-4 cylinders respectively so i think I have some other issues there aswell..

Strange as it may sound, consider yourself lucky. Changing caps and/or plugs is one of the easiest (and cheapest) ways to make your motor run better.

I think my safest bet so far is to get the standard points system running properly (new points and condensors) with either 5ohm coils or Hondaman's resistor pack and the 3ohm coils I currently have..

It's always wise to first make the standard system function properly before spending money on other things.
As far as the ballast resistors, you could first check without them how much Volt is lost between the Battery + and the + side of the coils due to aged wires (like on my bike). My idea is: Hondaman's suggestion is good as long as your wires are as new and there isn't any further impedance that results in voltage loss. If I remember well back then Bosch had various ballast resistors in the market (like 1,2, 1,4 and 1,8 Ohm.) Below a pic of the socalled 'superbobine' Bosch had. These were red, the regular bobines were blue. The ballast resistor is also in he picture.

[Bodi]

The only reason to use the 2Ω resistor is to reduce ignition current. Someone gets 3Ω coils because "oooh! more spark!" and then finds the resulting perpetually dead battery annoying. Resistors are cheaper than replacing the coils with proper ones. Some Honda OEM bike coils that look the same as original are lower resistance as well.
The coils work on current so spark energy using a resistor that takes it back to 5Ω total resistance will be close to just using a 5Ω coil. And, if still using points, the points will stop burning out rapidly.
And... I have to call Shenanigans! on anyone who claims a CB500 with Dyna S, 3Ω coils, and a 55/65W H4 always-on headlight keeps the battery charged. "In principle the charging system can handle it" - NO! ... this load is roughly equal to the maximum alternator output (at 4000 rpm+) with a perfect wiring harness. Normal riding will not keep a full charge on the battery. Losing the extra load from the Dyna's electronics power and loooong dwell might swing the balance for you (no details given on your homebrew transistorized ignition) but it will still be dodgy.

[flatlander]

well, rosewood wants something "on a budget" and wants to ride through city traffic so to keep it simple i repeat: get OEM or 5ohm coils, stick with points and get it to work well in that config. then you'll know that the basics are good and can move on to modifications if you want.

for the record, i measured the gill coils that came with my boyer-bransden micro power ignition, they're 4ohm. i don't know dwell or other details of the boyer. i have a 55/60 watt H4 bulb in the headlight, always on. and no problems with battery charging.
i also don't ride much in town of course...

[HondaMan]

It could be there is an advantage in using 3 Ω coils in combination with a ballast resistor. I have not understood this yet. Maybe Hondaman can shed some light on this.

Here's the skinny about using the resistor(s): the Dyna coils make about 35kV at 12 volts supply. The OEM coils make about 7.5kV under the same circumstances. The engines (especially the 500/550) need only about 4kV to fire. So, with fresh sparkplugs, anything more than 4kV is "excess margin", which is a design criteria used to measure the reliability of a spark system under adverse conditions. Most cars use a 50% "excess margin" value to be able to reach 100,000 miles on a set of typical sparkplugs, which presumes 0.0005" burn-off of the electrodes per 1,000 miles (causing a gap growth of .05" over that time if the plugs are not changed or serviced). This has been a benchmark since the days of the Kettering Ignition in US cars, around 1935 or so.

Applied to the Hondas we have, they use a (7500-4000)/7500= 47% "margin" value, pretty close to the same. But...the cars usually have 30kV coils, too! So, this number is reduced (non-linearly) by physics, nudging the REAL margin down to about 30%. In 'real life' this means: when the plugs start to get dirty, there may not be enough excess energy in the OEM coils to zap away the fluffy carbon, and the plugs start to foul.

So, what to do? In the 500/550 engines, this was resolved by making the sparkplugs a little hotter ("7" heatrange while all others are "8") and some more spark advance was added to reduce the pressures at the time of spark. This helps prevent flameout issues is the engine is lugged at low RPM, but it also tends to cause other problems (see my "Gentleman's Express" build for more details about that). Honda also used a slightly hotter coil (8.3kV, 4.3 ohm primary) in this bike to help it along.

If a fast-discharge coil like the Dyna 3-ohm is used, the higher voltage helps burn off the residuals and increase the margin, but the excess current needed to fire them is more than the bikes can muster. So, adding some series resistance (aka "ballast resistor"), as is found in most cars, reduces the overall current draw while still preserving the fast discharge and most of the higher spark voltage. In the Dyna coil (which are the only 3-ohm coils I have tested so far), adding a 1.0 ohm resistor lowers the output to about 30-31kV, while a 2-ohm resistor makes it about 25kV. Clearly, this is still much more margin than is found in the OEM coils.

But...the hotter spark comes at a cost: the energy discharges MUCH faster, so the spark duration (that is, how long the arc actually lasts) is much shorter, as the total wattage available is limited by other factors (like wires, time, etc.). The OEM coils discharge at about 1.25-1.40mS over the range of 1000-10,000 RPM, while the Dyna shows about 0.85-0.91mS over the same RPM range. This gives less time for the spark to ignite the moving fuel mixture.

In the 750/350F/400F engines, this duration is a BIG deal. They are all swirl-charge engines, while the 500/550 head is not quite so much swirl as it is tumbled, rather like a wedge-head design (think: Chevy 350 or Ford 360 engines).

So...the 500/550 can benefit from the higher voltage IF the duration can be stretched out a bit: this is where the resistance in the sparkplug caps (and sparkplugs) comes into play. If the plug caps are, say, 7500 ohms like they were in the 500/550K engines, the Dyna duration can be stretched out closer to 1.0-1.15mS: if you [today] use both the standard 5000 ohm plug caps AND the resistor-type sparkplugs (like DR7EA or XR22ES-U) of 2000 ohms, you can get some more duration out of it. This also cools them off somewhat, as the Dyna coils do run hotter than you can touch at 1000-3500 RPM speeds.

All this put together: when I 'build' a Dyna-coil system like this for someone on a 500/550, it goes like this:
1. 2.0 ohm Resistor Pack for the coils.
2. 5000 ohm sparkplug caps.
3. ND #XR22ES-U sparkplugs (sometimes listed as #X22ES-UR instead).
4. Copper-core spark wires.
5. Transistor Ignition, to get the most at all RPM ranges and cool off the coils some more (and prevent points wear!).

For a while, I was going to offer a package like this, but I haven't the $$ on hand to put together such 'kits' myself. Instead, I'll just tell everyone what I would do?

[Deltarider]

And... I have to call Shenanigans! on anyone who claims a CB500 with Dyna S, 3Ω coils, and a 55/65W H4 always-on headlight keeps the battery charged. "In principle the charging system can handle it" -

But I'm not running a Dyna or any other electronic ignition and I don't know of any 55/65 watts halogen btw. I love my points and in combination with a transistor ignition module like Hondamans in principle there's no problem having a 55/60Watts H4. That said, European models didn't have those silly no good running lights (in the blinkers) that waste an extra 16 Watts. Have a look at p.94 in the Honda Shop Manual Cb500-550 if you will. In the scheme in the bottom you see that at 3.000 rpm the battery terminal voltage is still no more than 13,2 Volts. Given that any '12' Volts battery is in fact a 13,2 (6x2,2) Volts battery, the conclusion is that even at 3000 rpm the bike is still not charging! Yes gentlemen, it's all in the riding I'm afraid.
With standard points in stock setup as well as in combination with my self built transistor ignition module I never had problems running a 55/60W halogen and since I live in the centre of town all my rides always include some city traffic. However if my bike would run at 3000 rpm or less for a considerable amount of time, I would think again and prefer to go by foot or hop on my bicycle. My bulb is the old Philips Vision Plus, that gives 50% more light than a conventional H4 and came out first in a test back then. It refuses to die and is around 15 years old now. If it ever dies, I will not hesitate and buy the Philips X-treme Vision. Great bulbs.