Help with ignition coils!

[gbeckhart]

Hello all!
I have a 82 GS650L. I am rebuilding the bike and have the coils off. While testing for resistance on both coils, the primary came out at 3.9 and 4.0 ohms. The secondary output gives me nothing..... I checked different combinations with the multi-meter touching one primary to one secondary, etc. Nothing! I even took the spark plug cap off and went directly to the wire. Am I checking the resistance correctly?

OK, so if the coils are bad, I need new ones. OEM are about $100 each. While searching I ran into ACCEL UNIVERSAL SUPER COIL KIT-4CYL INDUCTIVE - PART # 140403 for about $200.00 for the pair including cables, caps, etc. Would these be any good? Is it worth the try? or go for the OEM? I also saw Niche Cycle Supply Suzuki/Kawasaki Classic Ignition Coil 12v for about $41 each plus the caps. But it says will fit gs750 but not 650! I read on some thread on this site that other brands will not be a good fit for GS650. I don't know why a coil for a gsx750 or gsx600 will not do for 650?

Can someone share some light with me on this? Thanks all, really appreciate!

George

[tom203]

"I even took the spark plug cap off and went directly to the wire. Am I checking the resistance correctly?"

you're probably having meter reading problems. Put your meter on 20k scale, with plug caps removed, stick meter probes into the coil's plug wires (you want to hit the internal copper wire)- you'll probably get a 12 kohm reading. Depending on meter, it will show about 12 in display.
Ignition coils are very durable

[Guest]

Some good advice given. , It's very, very rare a stock coil fails, especially both at the same time, unheard of. If you do need some new coils just put a parts wanted ad up, there'll be a million of them on here as a bunch of use switch to Dyna coils at some point but really the stock coils work just fine.

[mike1414]

I'd like to briefly reignite this thread - I was having the same problem as gbeck, but even with my meter on 20k and touching the copper wire I got a "0" reading whereas my primary reading came out to be about 4.2 on both sides.

Let me me preface this by saying my '79 550 is having right sides sputtering and dying when choke is let off or when throttle applied. I don't know what the issue with gbeck was, but this Sounds very coil-y to me, although a "0" reading bilaterally for my secondary test doesn't make sense. Thoughts?

[tom203]

A secondary reading of 0 wouldn't produce a spark. Sounds like you are having carb problems.
Measure and compare readings on both igntion coils. You are measuring plug wire to plug wire (the copper) on the coil?

[mike1414]

It was my first time testing coils, but I followed this guys advice:

http://youtu.be/rRQ45lT2d3c

interestingly enough, I extensively cleaned my carbs beforehand, twice as a matter of fact. It was running great, then I went to start it up one morning and the right sided sputtering began out of the blue.

when I tested coil #1 I think it read 4.0 and coil 2 read 4.2

[tom203]

Your 4 cylinder suzuki uses the "wasted " spark approach- each ignition coil fires two spark plugs at once. Check them like I told tbe other guy...

"Put your meter on 20k scale, with plug caps removed, stick meter probes into the coil's plug wires (you want to hit the internal copper wire)- you'll probably get a 12 kohm reading. Depending on meter, it will show about 12 in display."

so it suddenly started running rough on right side..... Does your petcock have vacuum fitting connected to one of those right side carbs, namely #3 ?

[mike1414]

It sure does, Tom. Think that could be part of the issue? Unfortunately I will not have time until Friday to check it, but I will do as you said and check the plugs as such.

[mike1414]

Call me dumb (remember, first time working with coils), but I could not for the life of me get the plug wires out of the secondary side of the coils to be able to test the internal copper wiring with my multimeter. I know often these wires are screwed in; my wires seem to be aftermarket, and they're glued in. Any idea how to get these things out? I twisted, I pulled, I prodded, all to no avail.

[tom203]

Probably stuck- pull and twist at same time. But someone might have silicone glued them.

If they ain't coming off, then you have to test over the caps. Corrosion gives you false readings, so try to clean the contact area (the thing that hits spark plug top) as best you can. Small 1/4 inch round file might work. Anyways , over the caps (measuring cap to cap ) look for about 20 to 35 kohm on each ignition coil. Compare left to right coil.

[60ratrod]

what they mean by testing the wires is testing them with the plug caps off. the plug caps should just twist off the end of the wire. Suzuki oem coils came with the wires glued in to them. from what I have read, the wires are a PITA to get out of the coil sockets. I would remove the caps, trim about 1/4" off of the end to get to fresher wire, and retest. as tom said, corrosion will give you false readings. I would also pull the plug on the carb that connects to the petcock and see what it looks like compared to the others. if it's black and sooty and the others are more of a tan color on the insulator, your vacuum diaphragm in the petcock has failed and is leaking down the vacuum line to the carb making it run rich, which will make it sputter/stutter off the line