coil selection

[79-GS550-L]

Ok I decided to make a new thread for this as it's getting away from the subject of my last thread. I've decided to upgrade to dyna coils, and I am trying to decide which ones to get...

First of all:
Dynatek says to use 5 ohm primaries with points systems, or 3 ohm primaries with a 1-2 ohm resistor in series. I believe my bike came with 3 ohm coils (I'll double check when I get home), but it also came with Ford TFI modules rigged up to the points (the TFI modules are just being used as solid state relays, so that lower current goes through the points to extend their life). When I started troubleshooting stuff I disconnected the TFI modules and went back to using the points in stock configuration. There was no noticeable difference with or without the TFIs. What resistances are 79 GS550 coils supposed to be? Do you think the PO had changed them from 5 ohm to 3 ohm? They look stock to me (spark plug wires are not detachable). If I get the 3 ohm coils can I use them both with and without the TFI modules? I don't really care about the modules, they don't seem to do very much and they kind of block airflow to the engine anyways, so I don't mind losing them.


Second:
I can't figure out what secondary resistance to use. I've read to use the green coils only, but they have 3 different 3 ohm green coils - ones with 14,400 14,000, and 11,500 ohm secondaries. I would imagine you'd just get a higher voltage spark with a higher secondary resistance, but maybe it would take longer to charge up the coil?

Finally:
Can I use either copper core or suppression core wires?

[Nessism]

The stock coils have somewhere in the range of 4.5 ohms resistance, which points at the 5 ohm Dyna coils. Many people get the 3 ohm coils and use a resistor since this gives you an upgrade path if you want to use the Dyna S breakerless setup at a later date. You might want to check the Z1 Enterprises site for some real world information about the different Dyna coils - they give specific part number recommendations.

My understanding is that you can use a solid core wire with the Dyna coils. Not sure what the advantages are to this setup though. Again, check Z1 for their recommendations.

Regarding the Ford buzzboxes, my opinion is to focus on getting the bike running properly without them first. You can experiment with them later and see if they add anything tanagable.

[SqDancerLynn1]

The dyna green 3 ohm coils are what you need. A 70 mopar balast resistor (2 ohm) will work if you still have points for the 5 ohms.. CHECK into Dyna's new line of coils as they are smaller. IF you use solid core wires you need to use the OEM type caps. Suppression wires, you can use what ever type of auto wires you want with the auto ends

[79-GS550-L]

The dyna green 3 ohm coils are what you need. A 70 mopar balast resistor (2 ohm) will work if you still have points for the 5 ohms.. CHECK into Dyna's new line of coils as they are smaller. IF you use solid core wires you need to use the OEM type caps. Suppression wires, you can use what ever type of auto wires you want with the auto ends

Thanks for the responses guys. Just a few more questions...

Which green 3 ohm dyna coils do I need? There are 3 different secondary coil resistances available. Also would I get a bigger spark from a 3 ohm coil and a 2 ohm resistor, or a plain 5 ohm coil? I'm trying to get the best spark possible here, I don't plan on upgrading to dyna ignition any time soon.

Where would I find one of these mopar ballast resistors? Unless I did my math wrong, they need to dissipate about 30 watts, right?

What are the "OEM type caps"? Do you mean the NGK spark plug boots? What is different about them, do they have suppression built-in? Do I need any kind of suppression at all if I don't have anything digital on the bike?

[BlackStar]

I don't know that you would be able to tell the diff between the 3 ohm coils with a resistor, and the 5 ohm coils. With the 5 ohm coils you would get the full 12V across the coils which in theory would give you a hotter spark. The lower secondary R would give a lower voltage drop once the arc was established. Bottom line if you run the points you will need about 5 Ohms on the primary or the points won't last long.

You can get the ballast resistors at any auto parts store, as well as summitt racing and Jegs.
The primary is not energized 100% of the time, it is a lower duty cycle, so the resistor can be a little smaller. As long as it is intended as a ballast resistor, you will be fine.

The NGK caps have suppression built in and are used with non-resistor plugs.

There isn't anything on the stock bike that is going to be interfered with by running no suppression, but everybody around you may get interfered with. You could run solid core wires and resistor plugs as well

[79-GS550-L]

I don't know that you would be able to tell the diff between the 3 ohm coils with a resistor, and the 5 ohm coils. With the 5 ohm coils you would get the full 12V across the coils which in theory would give you a hotter spark. The lower secondary R would give a lower voltage drop once the arc was established. Bottom line if you run the points you will need about 5 Ohms on the primary or the points won't last long.

You can get the ballast resistors at any auto parts store, as well as summitt racing and Jegs.
The primary is not energized 100% of the time, it is a lower duty cycle, so the resistor can be a little smaller. As long as it is intended as a ballast resistor, you will be fine.

The NGK caps have suppression built in and are used with non-resistor plugs.

There isn't anything on the stock bike that is going to be interfered with by running no suppression, but everybody around you may get interfered with. You could run solid core wires and resistor plugs as well

ok I think I will probably get 5 ohm coils then, since I don't want to take my chances with a potentially weaker spark. And I'll get suppression wires too so I can use normal boots. Actually, can I use the NGK boots WITH suppression cables? Or is that too much suppression? I don't know which other boots to get that will fit NGK plugs.

I'm still confused about the secondary resistance. For 5 ohm coils they have 17,000 ohm or 14,000 ohm. Z1 sells the 14k ones. Is this ok? Wouldn't the 17k's have a higher voltage resulting in a better spark? Should I find some place to buy those instead? Dynatek lists those as cheaper than the 14k's.

[BlackStar]

I would'nt use the NGK boots with suppression wires. Too much R. Any boots will work with the NGK plugs. You may have to install the little thread on stud sleeves on the plugs. Dyna makes a reasonably priced set of wires.
If I remember correctly I went with the 14K coils.
Z1 is great to deal with. Ask them any questions you may have as well.

[79-GS550-L]

Now I've got to thinking... What happens if I use 3 ohm coils instead of 5 ohm? Will it just wear out the points faster? Or can it actually damage the (expensive) coils? Will the coils overheat with the amount of dwell the points provide? And does anyone know whether the ford modules will handle 3 ohms? From a little reading online it appears that they will do as low as 1 ohm. So now I'm thinking I should get the 3 ohm coils and hook the ford modules back up. Does that sound like a good idea? Remember they are driven by the points so they have the same dwell. Z1 has the green DC1-1, 3 ohm primary and 14,400 secondary. This sounds to me like the hottest spark possible if it works :-D Also, will my charging system and new 14Ah battery handle that current draw? It's 5A/coil instead of 3A/coil, but I have no idea what the actual duty cycle is.

[79-GS550-L]

It just gets weirder The coils I have on there now have 1.1-1.3 ohms primaries, and 31-34k secondaries. That seems waaay off, but sounds like they'd make a huge spark. Well I noticed that if you close the points for a sec with a screwdriver then let it go you get a nice blue spark. But when kick starting it's quite a bit weaker, and when using the starter it was non-existent (although now with my new battery I can actually start the thing with the starter :-D). So does that mean that my points' dwell is too short to fully charge up those coils? I have the gaps set to what the haynes manual recommends, brand new points and new condensers.

It makes sense that with 1.5 ohm coils drawing almost 10 amps peak I would see a decrease in spark when cranking or using the headlights. I am still thinking of getting the 3 ohm dyna coils and wiring the FTI modules back in. Maybe I'll have to play with the dwell a little bit too. Should I just set the gap as large as possible while still having a good spark at high rpm?

[SqDancerLynn1]

TFI module not sure what that is, bet that is why you have 1.5 ohm coils Go to any auto parts & ask for a ign balast resistor for like a 77 Ply - their all the same. It is 4 prong, just measure which side is 2 ohms. Mounted mine on top of the breather cover using a 3/8" stack of washers & longer bolt. Both 12 V wires to one end of resistor, other end of resistor feeds 12V to both coils

[79-GS550-L]

I just got a set of DC1-1 3 ohm dynatek coils. I put them on the bike yesterday, hooked up some old slightly fouled spark plugs, I had normal (blue) spark on two and a REALLY bright blue-white flash on the other two! Awesome! So I hooked up the TFI modules, put everything back together and fired it up......... perfect! It fixed pretty much every problem with my bike (except for the brakes, of course). So I went for a short ride around the block... it fixed the 2k rpm hanging idle, and the way it would die under 1500-ish rpm, and how it didn't have enough power to creep forward when I let out the clutch a little. Sweeet. Unfortunately, after a couple trips around the block the hanging idle returned. I'm hoping a carb sync will fix that.

It still felt like it didn't have much power at 1/2 throttle or so, and a bit of backfiring or popping or missing (I don't know what) near full throttle. When I got home I pulled the plugs and they were completely 100% black. I guess now I need to adjust the carbs. But I'm very excited about how much of an improvement those coils made!

[Nessism]

Hanging idle indicates lean condition. Most common reason is air leaks, with intake boot O-rings being the leading cause. Second leading cause is mixture adjustment.

BTW, I've got a large bag of intake boot o-rings and could send you some if need be. Send me a PM if interested.

[79-GS550-L]

Thanks nessism, but I just replaced those. That was my first thought. I've quadruple checked every possible way for air to leak, boots, o-rings, hose clamps, vacuum ports... everything is sound. It must be my mixture then.