Author Topic: Callin all Masters - 3 ohm v.s 5 ohm coils (Read 18740 times)

RpBet · « **on:** February 10, 2011, 12:40:48 PM »

I have been researching the site all week and found many opinions about whether to run 3 ohm dyna coils or 5 ohm. Within all the differences of opinion I have found a lot of useful info. There are however a few things that I need cleared up. Any help is APPRECIATED

I currently have stock set-up on my 78 cb750K. I want to make it as reliable as possible. Therefore in the future I will be purchasing a Dyna ignition. My questions are:

In the mean time I need to replace my coils so should I get 3 ohm or 5 ohm coils?
Does the Dyna ignition run sufficiently with 5 ohm?
I am getting a regulator so could I run 3 ohm w/out worry of killing my battery?

Thanks boys.

Skunk Stripe · « **Reply #1 on:** February 10, 2011, 12:44:11 PM »

The dyna will run absolutely fine on 5ohms. I am doing it right now. 3ohm work just fine too. Some see a difference, some do not.
As long as your charging system is in good shape and connections are clean and tight, you will be just fine if you run 3s.
I am going to switch to cb900 coils this spring and switch some light to led lights. Mainly just because for the lights. Something different.

ksmith0034 · « **Reply #2 on:** February 10, 2011, 12:48:49 PM »

I have a Dyna S ignition and 5 ohm coils on my '71 CB750. I did a TON of research before buying my coils, and the conclusion I came to after all my research was this: 3 ohm coils tax these old electrical systems quite a bit more than 5 ohm coils, and there is no noticable benefit whatsoever to running 3 ohm coils.
My conclusions, yours may vary.

Skunk Stripe · « **Reply #3 on:** February 10, 2011, 12:55:12 PM »

As I said, depends on who you talk to. Some have noticed no improvement, while others have. The later charging systems though are supposed to put out more power than the earlier bikes.

bollingball · « **Reply #4 on:** February 10, 2011, 01:27:54 PM »

Skunk by later what year are you talking about I thought all the SOHC put out the same except the (AUTO's). RpBet have you looked into the HondaMan system?

Duke McDukiedook · « **Reply #5 on:** February 10, 2011, 01:28:21 PM »

Original system- go with 5 ohm coils.

Deltarider · « **Reply #6 on:** February 10, 2011, 01:44:29 PM »

Strangely enough I have never experienced problems running 3 Ω coils on my 500, not with points, not with a simple transistor ignition module. As I said before I'm surprised there's so much talk about charging problems in this forum. I even run a 55/60W halogen and have never depleted my battery but - on the contrary - always returned fully charged. My rides are 20 minutes minimum.

One of my Dyna coils died already after 30.000 kms and I had to buy a new one (bloody expensive). The original Honda coils that I keep in the basement are still in working order after 70.000 kms of service. I have not detected any special advantage in a Dyna coil that another coil cannot offer. The possibility to screw on new cables is an advantage shared by many other aftermarket coils. I've the feeling Dyna knows how to market their products, for instance by stressing the 36.000 Volts that no one but a drag racer will ever need.

Skunk Stripe · « **Reply #7 on:** February 10, 2011, 02:14:23 PM »

I would not necessarily go with dyna coils either. They usually are ok. Probably stay away from accel it seems.
The 77/78 are reported to have a higher output alternator.

mick750F · « **Reply #8 on:** February 10, 2011, 03:01:16 PM »

If your goal is to make it as reliable as possible then consider HondaMan's ignition system... http://forums.sohc4.net/index.php?topic=67543.0 ...with 5 ohm coils. You can also run 3 ohm coils with his system if you add his resistor pack. That being said, I've been running Dyna 3 ohm coils with Dyna's ignition for several years with no problem but I'm considering going back to points with HM's system. The upside of that move is to get back on the road easily SHOULD the system fail.

Mike

wannabridin · « **Reply #9 on:** February 10, 2011, 03:37:46 PM »

Mark (Hondaman) said that my 3 ohm coils would work just fine with his ignition box and a resistor pack. so that's what i ordered, and i'm thinking this will work out JUST fine. i got the 3 ohm coils because i couldn't pass up on the deal, otherwise i would have probably gone with the 5 ohm just to save the $15 on the resistor pack.

Roach · « **Reply #10 on:** February 10, 2011, 04:03:41 PM »

Quote from: wannabINDUSTRIdin on February 10, 2011, 03:37:46 PM

Mark (Hondaman) said that my 3 ohm coils would work just fine with his ignition box and a resistor pack. so that's what i ordered, and i'm thinking this will work out JUST fine. i got the 3 ohm coils because i couldn't pass up on the deal, otherwise i would have probably gone with the 5 ohm just to save the $15 on the resistor pack.

so did it work out just fine?

iv had horrible problems with my 3ohm coils and dyna s cant even make it around the block without my bike craping out.

went to stock coils with dyna s works great

wannabridin · « **Reply #11 on:** February 10, 2011, 04:34:08 PM »

i don't see why there would be any problems using the 3 ohm coils. unless you have a bad batch of coils, there shouldn't be a problem. Hondaman said he's used them before with no problems, and i've ready elsewhere in more than one place that this combination will and has worked out well. of course, i won't know for awhile, being as my bike is torn down almost as far as it can be and pieces are all over the country

i'm hoping this will change ASAP!

Duke McDukiedook · « **Reply #12 on:** February 10, 2011, 06:39:38 PM »

Running 3 ohm coils conked my killswitch out, melted the switch.

Spanner 1 · « **Reply #13 on:** February 10, 2011, 10:20:58 PM »

I currently have stock set-up on my 78 cb750K. I want to make it as reliable as possible.

The proven answer to the above question is to stay with your stock coils and points... or spend your money as you will...

wannabridin · « **Reply #14 on:** February 11, 2011, 12:54:26 AM »

From what I've read, the hondaman box helps remove a good amount of current from the stock switch... And isn't there a way to run the coils off a relay to avoid the current through the kill switch??

dave500 · « **Reply #15 on:** February 11, 2011, 02:01:27 AM »

Quote from: Deltarider on February 10, 2011, 01:44:29 PM

Strangely enough I have never experienced problems running 3 Ω coils on my 500, not with points, not with a simple transistor ignition module. As I said before I'm surprised there's so much talk about charging problems in this forum. I even run a 55/60W halogen and have never depleted my battery but - on the contrary - always returned fully charged. My rides are 20 minutes minimum.

One of my Dyna coils died already after 30.000 kms and I had to buy a new one (bloody expensive). The original Honda coils that I keep in the basement are still in working order after 70.000 kms of service. I have not detected any special advantage in a Dyna coil that another coil cannot offer. The possibility to screw on new cables is an advantage shared by many other aftermarket coils. I've the feeling Dyna knows how to market their products, for instance by stressing the 36.000 Volts that no one but a drag racer will ever need.

im with delta here,i run a 55/60 halogen,my battery is near three years old and fine,i have a voltmeter and can see if through slow going traffic if the charge rate drops i can kill the head light,the voltage picks up straight away once moving again,im using stock coils on a boyer ignition,im not keen to buy dynas for any improvment because there wont be any,if i had to though id use the 5 ohms,because thats what boyer recommend for the system and also if i want to use points i can.

fastbroshi · « **Reply #16 on:** February 11, 2011, 02:19:48 AM »

From a a conversation I had with Mark:

Quote from: fastbroshi on January 06, 2011, 03:43:34 AM

Hey Hondaman,

I was wondering if you could clarify something for me. I have a basic understanding of why upgraded coils exist; to push out a fatter, higher voltage spark. I'm not sure exactly why this is needed though. If the originals aren't "leaking", is it possible the metal can fatigue in someway after so many years? Stands to reason that if they were good enough from the factory for the bikes' electrical systems, why wouldn't they be now?

Thanks,
Tim

Quote from: HondaMan on January 06, 2011, 08:28:27 AM

You're on the right track, Tim, at least as far as the "K" engines are concerned. The Honda coils make a LONGER duration spark, while the aftermarket coils make a shorter, HOTTER spark. In these swirl-charge engines, the longer spark is more desirable because the mixture is whizzing around in a little whirlwind (that's the 1960s Honda term for it...) inside the cylinder as it is compressed. The longer duration spark ignites a wider flamefront than the hotter, shorter spark.

In many older (vintage) engines, the coils used to be pretty weak. British bikes were especially bad about this item. Honda's coil voltage is about 7000 volts, which can jump up to 0.030" at 9.0:1 compression, and since the average car of the era had 20,000 volt coils, everyone thought this was too weak. Truth is, car coils emit an extremely short spark, because of the distributor-based distribution of the spark, so they need a hotter spark to make the trip, and to drive a wider gap in the hopes if igniting more fuel. Honda's method in the SOHC bikes was to move the fuel past the spark instead, so much less spark voltage was needed.

When the later SOHC engines came out, they went to a more hemi-head design that had less swirl. It still has some, because the intake ports are angled into the chambers, but without the guiding ridges inside the chamber, the later ones have about half the spin velocity of the mixture. Thus, many riders see an improvement with the hotter spark in these heads, IF they also open up their spark gaps to numbers like 0.45" or more. In reality, this wider gap is what is making the improvement over the stock coils, but touching more mixture: it just takes a lot more voltage to be able to jump that gap.

So, in a nutshell, that's what it is all about: it's pretty engine-dependent.

I think where he differentiates between K bikes and others, he's talking about the 750s. To my knowledge the head design of the 550s of all years was identical in regards to the combustion chamber shape.

ksmith0034 · « **Reply #17 on:** February 11, 2011, 04:33:15 AM »

Does that mean I should be gapping the plugs on my K1 at 0.45"?

fastbroshi · « **Reply #18 on:** February 11, 2011, 04:36:26 AM »

Sure why not. See how it feels to the seat of your pants.

dave500 · « **Reply #19 on:** February 11, 2011, 04:56:01 AM »

set the gap standard,but file the earth electrode back so it exposes about 50%or less of the centre electrode,this is an old hot rod trick and costs nothing.

Kong · « **Reply #20 on:** February 11, 2011, 05:47:45 AM »

Find the specifications for your bike and look up the Alternator output. I have looked at a few recently and they are not all the same model to model, my '77 CB550 as an example puts out a little over 10.5 amps at 2,000 RPM and above. Once you know the output add up all the power draws on your bike. Assume everything is running at once, with the high beam on, and add up the draws to give you a power consumption number. The alternator either makes enough power or it does not. It really doesn't make a hoot in hell what anyone's opinion is, just look at the numbers. That's why we got 'em.

On the burned up Kill Switch, that happened because the contacts were dirty, not because of 3-Ohm coils. Dirty contacts present greater resistance and that resistance causes heat, more corrosion, more resistance, more heat, and finally it burns up. As evidence we note that the Kill Switches are the same on all models of bike so if it had been the 3-Ohm coils that burned up your Kill Switch those same coils would also have burned up every one else's Kill Switches who used 3-Ohm coils - but that hasn't happened.

Deltarider · « **Reply #21 on:** February 11, 2011, 06:51:37 AM »

Looks like the Killswitch after all that killing commited suicide.

Deltarider · « **Reply #22 on:** February 11, 2011, 06:56:09 AM »

Quote

set the gap standard,but file the earth electrode back so it exposes about 50%or less of the centre electrode,this is an old hot rod trick and costs nothing.

Sounds interesting. Makes sense. Any minuses?
Does any of you guys have experience with Denso's new Twin Tip plugs? They're much cheaper.

Skunk Stripe · « **Reply #23 on:** February 11, 2011, 07:03:07 AM »

You have a number for those densos? I have been thinking about getting iridiums but if these are ok and cheaper, I might try them.
It also says to do that on the cyclex page with the electrode strap. I might try that on my old D8 plugs but I might not notice anything with those.
As for gap, I tried a wider gap with my dyna s and stock coils and I had to move it back to .030, anything more than that caused rough running.

Deltarider · « **Reply #24 on:** February 11, 2011, 07:21:00 AM »

Quote

You have a number for those densos? I have been thinking about getting iridiums but if these are ok and cheaper, I might try them.

Nope, that is... couldn't find any... not yet.

RpBet · « **Reply #25 on:** February 11, 2011, 08:27:06 AM »

I love this site! You guys are awesome. My questions have been answered plus some

.

Thanks to all. I will check out Hondamans set up. Fastbroshi really I appreciate the info and tips.

I have decided to go with 3 ohms, manly because of Hondamans information regarding late model 750's. And they don't get any older than my SOHC. I know I said I wanted "as reliable as possible" however, I was looking to advance my system slightly with the dyna ignition. Plus I personally am not a fan of the points system.

Thanks again to all!!!!!!

Skunk Stripe · « **Reply #26 on:** February 11, 2011, 08:34:22 AM »

I will see if I find anything for those denso plugs.

Roach · « **Reply #27 on:** February 11, 2011, 09:07:58 AM »

RpBet you have a PM

fastbroshi · « **Reply #28 on:** February 11, 2011, 12:01:52 PM »

Quote from: ksmith0034 on February 11, 2011, 04:33:15 AM

Does that mean I should be gapping the plugs on my K1 at 0.45"?

Sorry, thought you were the original poster and had the 3 ohm coils. If you set to that gap with your 5'ers, I think you may have inconsistent spark.

wannabridin · « **Reply #29 on:** February 11, 2011, 01:12:14 PM »

i wonder what the proper gap would be with 3 ohm coils, iridium plugs and a Hondaman box??

Skunk Stripe · « **Reply #30 on:** February 11, 2011, 02:04:16 PM »

I think it is something to test but on most cars with their high energy sparks that top 60,000 volts, it seems to average around .045.
I would probably not go over .035 myself but who knows, maybe .040 works.

Kong · « **Reply #31 on:** February 11, 2011, 04:17:35 PM »

I believe Dyna rates both the 5- and 3-Ohm coils at 35,000 volts - I know, it doesn't make any sense to me either.

dave500 · « **Reply #32 on:** February 11, 2011, 10:49:31 PM »

Quote from: Deltarider on February 11, 2011, 06:56:09 AM

Quote
set the gap standard,but file the earth electrode back so it exposes about 50%or less of the centre electrode,this is an old hot rod trick and costs nothing.
Sounds interesting. Makes sense. Any minuses?
Does any of you guys have experience with Denso's new Twin Tip plugs? They're much cheaper.

place a hacksaw blade or similar to protect the centre electrode as you file, and file nice and square with finesse,de burr and blow it out with compressed air after,itll expose a little more spark thats otherwise shrouded,im sure some older hot rod fellas will know this old one?it works best at cruise and light throttle,dont expect to be suddenly doing wheel stands,im not one for twin electrodes,the standard singles do as good,i like denso with the groove in the earth electrode.

Deltarider · « **Reply #33 on:** February 12, 2011, 12:12:04 AM »

Quote

,im not one for twin electrodes,

No, no, that twin tip spark plug doesn't have an extra electrode. It has a tip of the precious stuff soldered on the earth electrode to save iridium.

Kong · « **Reply #34 on:** February 12, 2011, 05:19:02 AM »

This discussion should be moved to the humor section. Split-fire plugs? You gotta be kiddin, right?

btriepke · « **Reply #35 on:** May 28, 2013, 05:05:50 AM »

I know i'm pulling up an old thread here, but i'm a bit confused. I have the dyna ign with "green" dyna coils. I assume 3ohm? The only marking on the coils are "12v 8-84" Should i have NGK Spark Plug Cap - XD05F - on the end of the wires, or just a regular spark plug wire? it says those NGK's are 5K Ohm Resistance?

i'm using a modern reg/rec unit if it makes a difference! thanks Trip

dave500 · « **Reply #36 on:** May 28, 2013, 01:34:23 PM »

yep use the 5kohm.

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Author Topic: Callin all Masters - 3 ohm v.s 5 ohm coils (Read 18740 times)

bollingball