1977 GT500 Ignition Coil Options

[oldjapanesebikes]

I'm sorting through bits and pieces from a parts bike and the project bike that I'm working on, and notice that on both bikes the ignition coils look to be fried - to the point that the casings have cracked open ! This specific coil part number (33410-15320/ 33410-15321) was only used on the 1976/1977 model years for the GT500. The secondary's measure open, so they are both headed for the bin.

My question is - although this coil is still available new from Suzuki, I'm wondering whether replacing it with two coils would not be better as I think they would run cooler, and if so, any thoughts as to which coils should I use ? The 1976/77 GT500 used a GT750 tank, so there is lots of room to install a pair, rather than the single as came from the factory. I have a stack of GT750/GT550 coils, but the ohmic value on the primary looks to be too high (about 6 ohms) to use on the GT500 with the stock ignition system Needs to be about 1 ohm on the primary, and 10 K ohm on the secondary.

Thanks !

[H2RICK]

Ian, those Triple GT coils have higher primary resistance, of course, because they're made for use with a points-style ignition.
You might want to look at some TEC coils from a CX/GL500/650. Those bikes (at least the later versions) came with CDI and so have a fairly low primary resistance. I don't remember what the secondary side resistance is but it would be typically in the 10K - 15K range so would probably work okay with the GT500 ignition.
Another choice would be from (I hate to recommend this) any 750/920/1000/1100 brand y Virago. They also use a CDI setup and their coils have the added bonus of using replaceable high tension leads. The mounting arrangement is quite weird but if you have lots of room that probably shouldn't be an issue.
Bring your meter to the shop and we'll have a dig through the bins.

[rbond]

Ian, I don't remember exactly the part number, I did have it mentioned on another post here. Anyway, I replaced my GT500 coil with a Dyna S unit designed to be used on a Harley. Put two wires that were short (distributor to coil length) to the plugs. Homebuilt CDI and this puppy has been running on that for two years and about 5k miles on the same plugs. Recently checked plugs and they both looked good, color and gap wise. I am consistently getting mid 40's mpg using it as my daily driver to work, errands, and even a little fun riding. The only thing I have not done yet was to go on a trip. (over 50 miles one way)

[tz375]

Unless 100% originality is vital, I would recommend Dyna coils. The come in 5 ohms for points, 3 ohms for some CDI and 1.5 ohm. I usually have pairs of 23 and 5 ohn around here but the only 1.5 I have are dual tower miniature coils and they pack a wallop plus they look much neater than the older style DYNA/KV coils.

If you have to keep a stock sort of look, you could do worse than a pair of GS500 coils which are usually dirt cheap. I can't remember the resistance but I used them with a GSX250 ignition on a CB77 racer recently with good results.

[oldjapanesebikes]

Many thanks for the input - looks like I've got a few options !

I'll be seeing Rick tomorrow to check what he has on hand, and if no joy there then I'll take the Dynatek route. Whatever I use will be out of sight under the tank so I can live with that so long as it works. I've downloaded their catalogue and will take a look this evening.

Robert - I found your post from a couple of months ago, and you mention that the coil you used was a DC6-1 (green 3ohm). I was wondering if you also ever posted the schematic for your home built CDI ?

[rbond]

No I have not posted it yet. I need to scan it and edit the thing for adjustments to the original. Board member Phil C from England was the engineer who helped me reverse engineer the OEM, then I built it. There is not much to the thing and it cost approx. $60.00 including a box to put it in. I have promised everyone here I will post, and I will, but down here there is much more riding weather........

[oldjapanesebikes]

.... but down here there is much more riding weather........

When compared to here, you've got that right !