Bad coils?

[Guest]

When I went to fire up my bike this spring it expressed displeasure at having it's sleep disturbed by only firing on cylinder #2, that's the only piece of the header that heated up.
No problem, thought I, a carb cleaning is in order.
Carbs cleaned, still only firing on #2.
For good luck, replaced the spark plugs. Still no joy.
Pulled the spark plugs, sure enough only #2 is sparking with the weakest most pathetic spark ever.
When I checked the coils with my multimeter, coil #2 (which is the one sending the signal to my only functioning spark plug) measured 4.67 ohms on the primary side and started climbing when I checked the resistance through the plug wires ending up somewhere in the neighbourhood of 412,000 ohms.
Coil #1 is at 4.61 and 31,600 ohms, which, correct me if I'm wrong, is in proper range but it isn't firing.
Seems to me that coil #2 has gone bad but it's still firing half of it's responsibility.
I'm ready to shill out for new coils if that's what I need but I'd like to be sure first. What should I do next?

[Nessism]

What kind of voltage are you getting at the coils? Some voltage drop is common and indicates corrosion in the harness connectors. A good many GSR members use a dedicated voltage feed from the fuse box to the coils, via a relay. I say this because the coils fire the plugs in pairs, and the spark performance you currently have is very odd and indicates a bigger issue than simply the coils.

[rustybronco]

coil #2 (which is the one sending the signal to my only functioning spark plug) measured 4.67 ohms on the primary side and started climbing when I checked the resistance through the plug wires ending up somewhere in the neighbourhood of 412,000 ohms.

Coil #1 is at 4.61 and 31,600 ohms, which, correct me if I'm wrong, is in proper range but it isn't firing.

Coil #2's secondary resistance is way to high. pull the plug caps off both leads and measure the resistance of just the secondary side of the coil. then measure each plug cap separately. the coil secondary resistance should read around 13-15 K and the plug caps should measure around 5K or slightly higher.

AND do what Nessism suggested... measure the voltage at the coils!

[Redman]

+1 for removing the caps on coil #2 and checking them. SHould be about 5K ohm each. Are available at any mo'cycle supply place, NKG brand anyway, doesnt need to be a Suzuki shop. Your reading on this coil secondary is way too high. THe caps do go bad and go bad by going higher resistance (and then going open).

The other coil seems okay ohm readings.

Done any other of the ignition checks (like in CLymer manaul, or Suzuki manual)?

.

[wincefish]

Alright...
Voltage at the coils is the same as the voltage across the battery ± 0.05v (12.87v)

Plug caps:
#1 = 9.6K Ω
#2 = 9.3K Ω
#3 = 13.6K Ω
#4 = 10K Ω (approximately)

Coils (secondary) without plug caps:
#1 = 12.6K Ω
#2 = 12.6K Ω

My conclusion is that I require new plug caps, can I get a second from someone who knows what they're talking about?

[tom203]

Alright...
Voltage at the coils is the same as the voltage across the battery ± 0.05v (12.87v)

Plug caps:
#1 = 9.6K Ω
#2 = 9.3K Ω
#3 = 13.6K Ω
#4 = 10K Ω (approximately)

Coils (secondary) without plug caps:
#1 = 12.6K Ω
#2 = 12.6K Ω

My conclusion is that I require new plug caps, can I get a second from someone who knows what they're talking about?

If you not using the coil relay mod, it's a miracle that voltage at coils is the same as at battery- there's bound to be a drop. Yes, your plug caps are high, but you said #2 was sorta firing. There must be something else going on here.

[wincefish]

While I've got plug caps on the way (for a couple bucks per might as well replace them and see what happens) does anyone have experience with rust in the ignition system and it's effects? I lost my ignition cover last fall and winter was unkind to the newly unsealed components. Could this be contributing to the issue? I sanded the rust off the end of the rotating contact, is that sufficient or do I need to delve deeper?

[tom203]

While I've got plug caps on the way (for a couple bucks per might as well replace them and see what happens) does anyone have experience with rust in the ignition system and it's effects? I lost my ignition cover last fall and winter was unkind to the newly unsealed components. Could this be contributing to the issue? I sanded the rust off the end of the rotating contact, is that sufficient or do I need to delve deeper?

It might have been helpful to disclose the missing cover/rust stuff in first post instead of focusing on coils. The signal coils might be damaged from corrosion - they don't carry much current, so the ignitor might not be reading them. They are magnetic but still rely on wire connections. Visit Basscliff's and review how to check things out in this part of the ignition circuit.