Topic: Discussed to death but needing a definitive opinion or two - 3ohm vs. 5ohm

[Tim.]

So I jumped on the Dyna bandwagon last night and installed the ignition.  Sure was satisfying getting rid of those points.  The Dyna just looks so cool and simple.

Now I'm going to explore new coils - if I go the Dyna route, should I go 3 or 5 ohm for the 550F?  Stock everything - no aggressive cams or bores.

Or, should I look at Accell or the like?

[Bodi]

I've used the 3 and 5 ohm Dyna coils, and I have not seen any difference in performance. I would just use the 5 ohm ones to save power. Dyna recommends 3 ohm for bikes that have the power available and the 550 qualifies, but I'd rather mount a bright headlight which would use up the extra juice.

[78CB750F1]

It may be worth checking with Dyna as to what they recommend - the tech guy I talked to claims that some of the Dyna systems work better with different coils.  For my GL1000 they recommended 5 ohm coils, and for the CB750 they recommended 3 ohm coils. 

[hymodyne]

I switched to dyna S and put a accel coils on an otherwise standard cb 500. I noticed an immediate increase in power and acceleration.

hym

[Tim.]

So if I go with a set of Dyna 5ohm coils, do I use resistor wires or just plain wires?  I'm a noob at ignition as you can tell.  z1enterprises sells both types of wire, and the only 8mm seems to be resistor.

[SteveD CB500F]

Why don't you ask Jeff Saunders at Z1 - he's a member here.

[scondon]

  I won't claim to know a THING about 550's, but I've run the Dyna S ignition on 750's with 3.0,5.0, and Accel coils. Also with suppression and non-suppression wires.  The 3.0 coils take more juice, as Bodi states, and since 5.0 coils work just fine for the stock set-up I'd stick with them(cheaper too). I don't think the Dyna S ignition signal is affected by your plug wire choice, I ran solid copper core(non--suppresion) with rubber plug boots and had no troubles(never checked for AM radio interference). Currently run 8mm suppression wires, but only 'cause I liked the color choices.

[Bodi]

To clarify, I don't notice any difference between the 3 and 5 ohm coils even on modified engines. But the Dyna ignition and either Dyna (or Accel) coil is a noticeable improvement over stock. I can't say for sure the stock systems were in 100% perfect condition or tune, but swapping to electronic has consistently improved starting, idle, and fuel mileage. Plus never having to adjust the timing or dwell again.
There's some risk of interference with solid wire, non-resistor caps, and non-resistor plugs. What happens is that the ignition double fires: when the 1-4 ignition fires from the sensor plate, the 2-3 ignition picks up the interference and fires also (and vice-versa). This isn't a severe problem (no backfires or damage) except the dwell time for both coils is cut by 1/2 and the spark is weaker at high RPM. You can add a ferrite bead on the power wire at the Dyna plate and help eliminate this effect but I would just use resistor plugs or 5K resistor caps (not both). I'm not a fan of resistor wire.

[scondon]

Good info. Thanks,Bodi

[Tim.]

Well, I took the plunge and made a deal for some Dyna DC8-1 coils for $50.  Figured that was a good price vs. $120.

Now I just need to choose some wire and plug ends - z1enterprises here I come!

Took the bike out tonight - need to fiddle with the timing on the Dyna and synch the carbs again, but it's running SOOOOO much better than before the rebuild.  I've only taken it up to 5000 RPM a couple of times, but it feels like there is so much power beginning at that range - can't wait to tap into it once it's broken in a bit.  Only have about 20 miles on the engine at this point.  First real ride was tonight.