Topic: 76' CB550 w/ Dyna S and 3 ohm coils, is my charging system going to explode?

[crinklesmith]

Alright, I have a 550k2 with a Dyna S trigger and Dyna green (3 ohm) coils. All other ignition components appear stock, including wiring. The bike was purchased with the system, and no reading material or receipts were supplied for reference. They look like they have been there for a while. At idle, with no accessories, and headlight on low, I'm getting ~11.7-12.0vdc, across the batt. terminals, and at 4 grand on the tach, ~12.5-13vdc. (Going off memory, I'll have real numbers by tomorrow.) This is a newer Yusa wet cell, btw. The bike runs great, and I have had no electrical problems, yet. I have basically a caveman's knowledge of electricity , and just read through about half of Hondamans resistor thread until my head exploded, and after picking up the pieces, I have two questions.

1. How can I make this setup as reliable as possible, for weekend touring and some commuting, (3-4k rpm cruising) and can I have a 1st grade level explanation as to how the parts needed to make this happen will work? Is this possible without sacrificing the "higher performance" of the Dyna components over the stock ignition?

2. Does anyone know where I can find literature for these parts? Internet or print?

Alright, so four questions then.

Thanks,
Will

[GammaFlat]

Some Dyna-S docs: http://www.mpsracing.com/instructions/Dynatek/Dyna_instructions.htm

[crinklesmith]

Thanks gammaflat.

[firefighter_zach]

Sorry to jump in on your thread but I also have a 550 with the green 3 ohm Dyna coils. Thinking about putting in an electronic ignition. Can I do this safely? O and what is the resistance on the stock coils?

[TwoTired]

I'm not a fan of Dyna.  More money than worth using my reasoning.

The stock coils have about 5 ohm for primary resistance.  The stock points only draw power for 195 degrees of crank rotation.  The Dyna-s draws power for 315 degrees of crank rotation.  Which is 154 % longer along with a higher draw than the stock bike expected.  This causes an increase in bike system load from 2.56 amps (33 watts) for the stock coils, 54% of the time (for each coil).  Total ignition draw is about 35.6 watts.
Compared to the dyna 3 and dyna-s combo which draws 4.2 amps (54.6 watts) for the coil 87% of the time (each coil). Total ignition draw is about 95 watts.  More than double the power draw.

The 550 has a 150 watt alternator when you spin it to 5000 RPM.  Stock bikes with the standard headlight on, draws about 120 watts for the whole bike.  The dyna setup adds almost 60 watts to this.  You will be relying on your alternator beating the factory minimum spec to keep the battery charged.  Some do, some don't.  Regardless, recharging will be very slow if you are lucky.

Then, if you consider that the alternator only makes about 40-50 watts at idle, the only thing keeping your bike running is the stored energy in the battery.  When that power is gone, you have a dark, lifeless bike.

The sad thing is, that unless you increase the spark gap at the plugs, or have engine mods to increase C/R, that "high performance ignition" isn't doing anything for you, except make the spark better when the battery is particularly weak.  The way the ignition system works on the SOHC4, it is the spark gap that determines the actual spark voltage, regardless of what the coil is capable of developing.

You can mitigate the excessive drain by adding an inline resistor to the coils to limit their current draw.  Probably better to get 5 ohm coils, though which dyna does make.

Anyway, no, your battery won't explode.  It would need some stored energy to do that.  Which seems low risk with an added Dyna ignition system, such as what you have now.

Cheers,

Btw, those battery voltage readings below 12.8 V shows a discharging battery.

[vames]

I had a friend with a 75 CB550/DynaS/Green 3ohm coils and despite cleaning every conection and keeping the headlight off during the day, it never did charge well -- constantly ran down. It became a matter of hooking it up to the battery tender every night and kicking it to start it most of the time.

Same setup on my 76 750F wasn't a problem, but I have to say I couldn't feel any difference when I switched from stock 5-ohm to dyna 3-ohm coils. Nothing -- I considered it a complete waste of money (except for being able to change the plug wires).

[crinklesmith]

Thanks for the replies guys, so it seems like the best solution here is to at least run the resistors, or ideally run 5 ohm coils, but this would only put a band-aid on the higher draw from the ignition trigger, correct? I was also skeptical about the ignition when I bought it, as everything else is stock and original, besides the exhaust. The only benefit I can guess at would be quicker starting, but having not owned a points sohc bike, I have no reference to base this opinion on. (This one starts first kick everytime, dead cold) I don't plan on running a .004 second 1/4 mile, or lapping GP bikes, so I would prefer the stock points over the Dyna S stuff just for the fixability, and be able to have a charging battery. The Dyna S uses the stock advance mechanism, correct? So it should be just a matter of finding a points plate and a set of stock coils, I think.

Anyway, no, your battery won't explode.  It would need some stored energy to do that.  Which seems low risk with an added Dyna ignition system, such as what you have now.

I should have gone with implode, or collapse into a electromagnetic singularity.

[vames]

Points can be an easy first-kick starter. And it's not really a performance issue either. Most people that get the Dyna S do it so that they never have to deal with setting points again -- hell, $120 for never having to set timing again is worth it to most people. I don't think the electronic ignition is a big draw on the charging system, so if you resistor up to the equivalent of a 5-ohm coil, your Dyna isn't going draw you down enough to notice (at least it doesn't on my cb400f, which has the weakest charging system of them all).

[edbikerii]

My first-hand experience with Dyna 3 ohm coils and Dyna-S ignition on 1977 CB550K:  They use too much power for the charging system.

Charging is fine with 5 ohm Dyna coils and Dyna-S ignition.  Not having to deal with points is great.

[TwoTired]

Points can be an easy first-kick starter. And it's not really a performance issue either. Most people that get the Dyna S do it so that they never have to deal with setting points again -- hell, $120 for never having to set timing again is worth it to most people. I don't think the electronic ignition is a big draw on the charging system, so if you resistor up to the equivalent of a 5-ohm coil, your Dyna isn't going draw you down enough to notice (at least it doesn't on my cb400f, which has the weakest charging system of them all).

The Dyna-s certainly has less impact than the 3 ohm coils.  But the dyna-S still increases the power draw for the ignition from 35.6 watts to 57.4 watts when using 5 ohm coils, by the vary nature of it's operating principle.  21 watts extra is more easily accommodated by the bike's system than an extra 60 Watts for the trigger and the 3 ohm coils.

Cheers,

[GammaFlat]

When that power is gone, you have a dark, lifeless bike.

I have to admit that reading TwoTired's replies make me laugh out loud.  I don't seem to realize it until I hear my parrot mocking me with his "parroting laughter".