Dyna S + 5 Ohm Coils

Does it make any difference to combine the Dyna S ignition with 5 Ohm Coils instead of the 3 Ohm coils?
It is for my 1977 Kz1000.
Thanks

I think its ok to use higher ohm coils, but do not go under 3.
someone want to verify this? Lou?

Hey antokan12 - I spoke with Jeff @ Z1Enterpises about this topic yesterday.

I have the 4.0 ohms green coils on my '77 650. My friend is running points on his '77 1000 LTD and he just picked up some 5.0 ohm coils from Jeff. According to Jeff, he indicated there is no problem with swapping the 5's for the 4's (on my electronic ignition set up) as long as you are not out running the bike on a race track at high rpm for extended periods of time.

Cheers-Colin Firth-Ontario Canada

1977 Kz650 Custom. Wiseco 810/750 Cams, valves, WG Mikuni 28's, and lots of other go fast goodies.

wiredgeorge's (joke; actually Ohms law) law states V= I * R which means voltage equals current times resistance. For 5 ohm coils... To figure out what the current delivered to the primary windings (amperage delivered) divide V/R or 2.4A will be the current delivered to your plugs (kind of) after the inductive electromagnetic magic of the coil perks up the voltage through the secondary windings. If you use 3ohm coils 12VDC is divided by 3ohms and 4A results... almost double the voltage and finally, the spark to your plugs. In reality, the 3ohm Dyna coils are about 3.8 ohms and the 5ohm coils are probably not much more than 5ohms so the difference won't be quite that large but you will get hotter spark with the 3ohm green coils than the 5ohm coils. Last, there is more heat generated using the 3ohm coils than the 5ohm coils but both are well within the safe range of operation for use with points or a Dyna S. You want to avoid lower resistance coils because of the heat issue... 1.5ohm coils can't be used for this reason.

Post edited by: wiredgeorge, at: 2006/06/23 10:13

that being said ,wouldn't the stock coils provide more spark due to there lower resistance (they are lower arent they?).can i use andrews coils off a kz650 on my 76 kz900,with martex electronic pointless egni.? does it even matter if you have points or pointless.?i burnt out one of my martek coils and one of my stock coils.can i run 1 martek and 1 stock coil until i can get some new ones without scerwing something up? it seems to run ok.

Post edited by: mark1122, at: 2006/06/23 11:46

Stock coil have lower resistance? Which stock coils? The old coils from a 76? They started life at about 4 ohms and today, you had best measure using a multimeter in the x1 OHMS position. I doubt they are 4 ohms today... more than likely higher as they tend to pick up resistance after 30 years of cooking. The OEM coils on other models may not be the same. The two KZ1000E (ST) that I own had coils that started life at 1.5 Ohms and required ballast resistors to bring the total impedence up to about ~3-4 Ohms. I just got done measuring the primary resistance on about half a dozen of those things and the lowest I found was about 4 Ohms varying up to about 8 Ohms... and that is from 1.5 Ohm (originally) coils. I have several ballast resistors and they are supposed to test to 1.5 Ohms and none tested under 5 Ohms... Old stuff is old stuff. If you choose to use old stuff, I suppose it would be best to actually measure the antique's resistance.

I will go for the 5 Ohm coils then. Thanks to all for the comments!!!

Beware the Martek ignitions are pretty sensitive. They have a rep for failure.

Dyna indicates 3-ohms is the lowest resistance coil to use with their ignitions. Higher ohms is ok for the ignition, but any coils used with the Dyna will get hotter than the same coils used with a stock ignition.

Post edited by: loudhvx, at: 2006/06/24 17:38