coil resistance

I'm trying to determine if I need to replace my coils. When I test primary resistance, I get a reading of 4.5 Ohms. When I test the secondary resistance, I get NO reading(off the scale). Both coils read exactly the same.
(Everyone, including the manual, is saying I should get readings of like 3.8 ohms.
In fact, if I use my other multimeter, it reads 5 ohms on both coils).
The bike runs, though poorly. I get great spark at plug #4, while all other cyls fire intermittently. I can smell gas, from the unburned fuel.
My bike is a 1977 KZ650 B1. I would like to know which Dyna S coils I would need to buy for replacement. Anyone else have the same bike with Dynas on it? And who has them the cheapest? Thanx

Since you have the original wires on your coils, they should be non-resistor type and if you get infinite resistance there would seem to be shorts on the secondary windings. I wouldn't think the primary impedence you measured would be too far off the scale but it is unusual that it is so high. Try www.z1enterprises.com for the Dyna coils. You will want to get the 3ohm w/two outputs. I am not sure what part number that is, but they are the green ones with two outputs. One of the main problems with the older coils is that the wires are epoxied into the bodies. The manufacturer pushes the wires down over a spike inside the coil and then pours in epoxy making the wires a misery to change. The Dyna coils will need new wires/caps and Dyna makes a nice set in a variety of sporty colors.

You might have a go at removing the old high tension wires and measure resistance between the two pins that are deep in the coil housing. Measured about 20k Ohms on my 1980 GS1000 coils. I got the old wires out by fileing the epoxy flush to the coil housing. Epoxy did not extend into the housing and the old wires came right out. Don't know about the KZ but the suzuki coil housing has holes that are a hair larger than the 7mm wire and there is a sleeve over the old wire that stayed in the housing. On mine it was not too difficult to dig out with a pick. Would have left it but it was a bit shredded. When I put it back together, I used some dielectric grease being careful not to get it near the top of the 'hole' or on the wire. Used some 3m weather strip cement AKA gorilla snot to secure the wires. Has been working great.

Total cost was under $20 including tax for four new NGK 5K Ohm boots and some non-resistance type 7mm plug wire off a roll at the autoparts store.

Measured about 30k between the boots after it was all back together.

I agree with WG that new coils would be a lot easier. I just didn't want to wait for them to come in the mail.

-Duck.

Infinite resistance means there is an open connection, not a short.

4.5 ohms is not way out of line for the primary resistance. In that range, a meter can be off by 1 ohm.

If #4 is getting good spark, #1 must also get good spark unless the sparks are leaking through the wires (or getting to the coil some other way which is very doubtful).

With the age of the coils, though, I would recommend new ones anyway. I've been stranded with two shorted coils in a rainstorm. They worked fine until they got soaked. Or I should say they worked fine until I got soaked.

Post edited by: loudhvx, at: 2005/11/10 12:21

Duck, I have dug the wires out of my coils before as well... seems most are different but they all seem to have posts that the hot part of the wire is impaled on and epoxy to hold them in... If you buy an Accel 8.8mm generic wire kit which gives you enough wire to do a couple bikes PLUS all the connectors, they give you clips that bite INTO the wire. You put the clip around the wire and when you press it over the wire, the clips bite through the insulation. They can be used for splicing NEW (and cute yellow) Accel wires to the old stubs. You just cut your old wires to about 2 inches or so and splice. I never felt very comfy about doing this though... I did go crazy and install some of those racy yellow wires on a bike once. I got over it and now use black 7mm Dyna wires.... hehe

Thanks for all the help!
As much as I hate to spend more $, I've got too much into this thing, not to spring for new coils. So I ordered 'em today. With my new coils, WiredGeorge carbs, Dyna S ignition, and WGeorge's "POWERING YOUR COILS DIRECTLY FROM YOUR BATTERY" circuit, I should be up & runnin' in about a week. Can't wait!

Post edited by: Wild & KZ Guy, at: 2005/11/10 15:34

Dammit! I'm too late!

I was going to suggest testing your plug caps -- the part that fits over the spark plug actually screws off of the end of the wire -- before spending money on coils. I had one go bad, which led to the same infinite-resistance reading as what you have. Pulling the cap off, and testing just between the ends of the coil wires, showed that the coil was good. $16 later, I had four new plug caps.

If you're willing to spend on new coils, more power to you. Just be sure to test your old plug caps if you plan on using them (along with your old wires), as they may have been the cause of the infinite reading. As someone else mentioned, Dyna makes wires which go with their coils (but are usually sold separately). If you ordered wires with the coils, you'll be fine.

WG-

Yes, I don't think I'd be comfortable with clip on wire extensions either. The GS1000 wires had been chewed by critters and the remaining insulation was brittle. More like something one would expect in a 1930's radio set. The coils were perfectly good and I'm such a tightwad, I couldn't bring myself to replace to spend tire $ on replacing good coils Things I don't mind spending $ on are factory manuals, suspension maintenance, good tires, and other consumeables.

I'm a bit ticked off at the moment. Was trying to scrape together $ for a second FT500 and a darn tree limb fell on my truck. Hit right at the top of the windshield opening. Big crease about 4" deep and 18 x 9 inch and broke the windshield.
There goes a day beating it out and painting it and who knows how many $ for new glass. Still way less $ than all the insurance I haven't been paying for...

-Duck

-Duck

Wow, sorry to hear about that tree limb. Damn that sucks!
I just took the coils off the bike. On the 2-3 coil, it was indeed a bad plug end/connection. #2 end wasn't connected at all. I came right off, almost fell off. I tried to stick the probe down directly into the coil wire, still couldn't get a reading; not until I cut about a half inch off the end of the wire. Then I got a 23K ohm reading.
As for the 1-4 coil, I couldn't get a reading until I removed both plug ends, even though they were really on there tight. Then I got a reading of 177K ohms! And the #4 plug was the only one firing nicely (off of this coil).
But both coil's primaries were reading 5.0.
Either way, I think it was money well spent on new ones, don't you agree? Jeff at Z1 is gettin' them out to me in a few days.

First off welcome aboard.

When you got the 177K ohms are you sure you had the meter on the correct setting? This could be just me but I always have trouble remembering which setting to use.

Anyways though, the new coils will be the best bet anyways.

Hey DanO,
You're putting too much thought into those multimeter settings. If you have it set too low,it would indicate that is is off the scale; mine just shows a '1' to the far left side of the screen(on an analog meter, the needle would rocket to one side of the gage). You just turn the dial up until you get a reading.
If, on the other hand, you have the range/dial set too high, it will give you a reading, though it will not be as accurate as it could be; By turning the dial down, it would move the decimal point over, for more accuracy; Example: say you are getting a reading of 12 volts. You turn it down one, and now are reading 11.8 volts. You turn it down once more, and you are reading 11.79 volts. If you went too far, and turned it down again, it would go off the scale, and give you an indication of that, depending on your particular multimeter(mine shows that leftside '1', as mentioned above).
Same deal with resistance readings; it will either be off the scale, or not at full accuracy. Just dial it in.
If you don't have a digital meter, you can pick a decent one up at Harbor Freight for around 5 bucks. Some people still like the analog/needle style ones better, because they don't require a battery(except for ohm/resistance readings). I think the digitals are worth it, much more accurate. Just keep an extra battery on hand(mine uses a 9v battery).
I agree with you though, new coils are the way to go in my case

Post edited by: Wild & KZ Guy, at: 2005/11/12 08:27

Ignition Update:
First off, I gotta say, this is kind of embarrasing.:blush: I'm only sharing it in the hopes it will help someone else.
Bottom line is; the plugs were bad. They looked new on the outside, I just assumed I changed them 2 years ago, when I first got the bike. I never gave it a second thought, when I was working on the ignition. When I finally did pull the plugs, #2 snapped right in half.
The thing that kept throwing me was that the timing light wasn't showing much activity on 3 of the cylinders.
I got a fresh set of NGKs in there, it starts instantly at the touch of the start button now. I actually got to take her out for the first time and do some riding yesterday. . .YEAH! :woohoo: :laugh: