Topic: dyna coils

[hotrod101]

newbie here.....can 1.5ohm coils be used on cb750k's? any way to use them....resistor, condenser???  any help really appreciated

thanks
john

[supersport_CB400F]

I have 3Ω coils and they take lots of battery power and get hot!… 1.5Ω I would use a couple of resistors about 10W from what I’ve read or the charging system wont replace the battery.

You need also to get rid of the points to uses those coils

[burmashave]

I have 3Ω coils and they take lots of battery power and get hot!… 1.5Ω I would use a couple of resistors about 10W from what I’ve read or the charging system wont replace the battery.

What kind of resistors, and where would I place them?  Or do you mean resistors in the plugs, wires, or boots? 

The reason I ask is that I'm using Dyna 2.2Ω coils.  I would have picked 3Ω coils, but it was a package deal with the Dyna 2k ignition.

[hotrod101]

biffta

10 watt resistors....how many ohms??

 has anybody done this....not wanting to burn up my ride??

thanks again

john

[SteveD CB500F]

Basic electrics:

Standard coils are about 5 ohms so at 14.5V run 2.9 amps.  Assuming that the original design is set up to handle this amount of current in the ignition, any reduction in the impedence of the coils will increase the current required from the system.  Low impedence coils give quicker, bigger, fatter sparks but at a cost. Ultimately the points won't be able to handle it and you will need a "contactless" system.

3 ohm coils will run 4.8 amps
2.2 ohm coils will run 6.6 amps

Putting a 2 ohm resistor in series with the coil will reduce the current but will bring the impedence back up from 3 to 5 ohms but will also negate the effect of the low impedence coil (so why bother)

The answer is to use low impedence coils with the electronic ignition.

To answer the question "how low?"  I don't know but I can imagine that 2.2 ohms is asking for trouble from the (barely adequate) electrical system.

3 ohm coils with Dyna ignition - probably OK (chip in everyone who uses htese with no probs)

I hereby relinquish the mantle. Two Tired where are you?

[KB02]

Okay, Steve. So, after your lesson in Greek , I'm still a little bit confused (Electronics is not my strong suit).

I am planning on putting a Dyna ingition in my bike this winter, Since I need a new coil anyway I was planning on replacing them with the system. What Ohm should I be looking for in a new coil?

[SteveD CB500F]

I wouldn't go below 3 ohms, but I'm an electronics engineer.   

There may be someone else on here who has tried it.

[dusterdude]

i believe the 1.5 ohm coil will work with the dyna 2k ignition,its just a matter of how well the charging sytem on our old bikes can keep up with it.

[burmashave]

Steve, thanks so much for the scoop.  2 amps is a huge difference -- I'm going to be shopping for some new coils   I don't want to put an additional 1.8 amp load on my system.

[SteveD CB500F]

I believe we have 140W alternators on our bikes (?)

4.8 amps (even at 12V) is nearly 60W

Turn on your headlight at your peril!!

[MRieck]

I know Dyna recommends the 2.2 coils with the Dyna 2000 but it is because of high RPM saturation time limits (12,000, 13,000, 14,000 RPM's). You won't be turning those RPM's ( or, if you do, not for long) so I would stick to 3 ohms. I use a Dyna 2000 with 3 ohm coils with no problems.

[Jerry Rxman Griffin aka MuthaF'er]

Mike,

I want to digress a moment but the coil draw issue is still relavent to the question. As Steve said "turn on your headlight at your peril".
Have you measured the voltage in your system with the 3 ohm coils? I'm wondering if your system will get up to that mythical (as I call it) 14.5V reading or how high it will actually go. I'm running Dyna 3 ohm coils and a halogen bulb and have been through all the diagnostics, etc including a replacement harness and still can't pull that voltage. Only thing I haven't done is replace my ignition switch (yet) but that is going to happen.

Jerry

[dusterdude]

i run 3 ohm coils off a yamaha or some such bike,i havent any charging issues as of yet.

[MRieck]

 Jerry
 The last time I checked I was real close, if not at 14.5. My stator is pretty new, the reg/rec is an Electrex unit and everything else tip top. I run a halogen bulb also. I recently switched to an LED rear light as I found one the uses 20 (or 24) LED's and puts out decent light. I haven't measured since then but I'm curious now.

[scondon]

   Rxman, I have the same experience as you running 3.0 coils and Dyna S ignition. Highest I've measured is 13V. Battery recharges just fine but signals can get kinda slow below 3,000rpm. Kicker is that I assume that the voltage spikes at some point as my battery boils down after 4 months of daily riding. I'm looking to try the Electrex and see if that doesn't help.

[Jerry Rxman Griffin aka MuthaF'er]

Sean & Mike,

Thanks for your input. This electrical crap has driven me absolutely insane trying to achieve the holy grail of 14.5V! Longest ride this year was 300+ miles with lot of high speed. Battery was fine when I returned & not drained so I'll stay away from traffic lights. I now have and use a Battery Tender while it's parked. Not putting a lot of miles on it however. TT was helping me shake it down and I accidentally cooked my Electrex RR24 so now I'm back to stock units. No difference with either. The guy in Oregon makes a unit and says it puts out higher voltage at lower rpms. I'd like to see numbers vs rpms pertaining to this unit from someone that is able to put out 14.5V. I'm using Dyna III by the way.  I don't have a set of stock coils or else I'd install them to see what difference that one change makes. After I replace the ignition switch I'm giving up on 14.5!

Jerry

[jaknight]

Well, I'll tell ya Pilgrims..........

     This all sounds very impressive and important.  Fascinating too.  I have a Dyna on my '74 cb750 K4, standard stock coils.......

     I know next to nothing about electrics.  Now......... I guess I would be happier than a duck chasing a June Bug if I knew what in the he** you are all talking about..........

     What are my stock coils churning out and how are the Dyna electronics doing with the stock coils?  The bike rides great and I haven't had any battery/charging problems........

     ~ ~ ~ jaknight ~ ~ ~

[Jerry Rxman Griffin aka MuthaF'er]

Dyna coils have less resistance ( Dyna 3 ohm for Hondas vs 5 ohm or 10 ohm Honda stock coils), throw a much hotter spark and use more electrical energy in doing so. Hotter spark should give you better performance especially at higher rpms and less chance of plugs fouling if you have this type of issue. I'll let one of the other guys explain the internal differences if necessary. Not sure that I could other than to say they are wound differently. Your Dyna ignition is much improved over the stock set up but replacing 30 year old Honda coils with new Dyna coils in conjunction with a Dyna ignition should have a noticable improvement in performance, starting and hopefully fuel mileage also. It's one of those upgrades you do when your stock coils or wires are shot or you just need to spend money.   

[SteveD CB500F]

In TT's absence I'll have a go.

Separate the coils and the ignition (contact breakers)

1. Replace points with a Dyna (or similar) = no maintenance and (maybe) better performance

2. Replace standard coils with Dyna (or similar) low impedence coils = fatter spark and (maybe) better performance.

You can do 1 without 2 but you can't do 2 without 1 as it will fry the mechanical points.


RX - you beat me to it but I'll post this anyway!

[dusterdude]

steve,dont mean to argue here,i installed my 3 ohm coils about a year and a half ago and havent had any points issues as of yet.

[SteveD CB500F]

Do they spark?

[Einyodeler]

I`m running a Dyna S, a halogen headlight and dual tailights in the `72 500 and my charging rate dropped as well,down to 12.9 volts.
I have the old style regulator so what I did was cleaned and regapped the points in the regulator and recalibrated it using the voltage adjusting screw, now I`m right back up at 14.5 volts.

[dusterdude]

Do they spark?

you talkin to me? .if so i dont understand the question

[Jeff.Saunders]

You can run 3 ohm coils with points, but they accelerate the pitting on the points.  Just be prepared to replace the points more frequently.

What we normally recommend is 5 ohm coils IF you plan on continuing to run points - and 3 ohm coils with the Dyna-S ignitions or if you plan on switching to a Dyna-S ignition within a few months.  If you run 5 ohm coils and switch to a Dyna-S in the future, there's no problem, although you will lose a very small amount of spark intensity - not enough to worry about on the street.

Dynatek recommends 2.2 ohm coils with the Dyna 2000 systems - although I do know a few people running 1.5 ohm coils with the 2000's on race bikes.  3 ohm coils will work also, although they do produce slightly less spark than the 2.2 ohm coils.

[SteveD CB500F]

I am always happy to be proved wrong by someone who has actually tried it Dusty.

I'm with Jeff - fit the ignition AND the coils...