Electrical wizard needed! Problems with ignition

[RRhoads]

I have a 1981 GS550L with about 9,900 miles on it. I bought the bike last year and took it to a friend of a friend to get it running. The bike is completely stock. The original carbs on the bike were junk, so I bought carbs off eBay that were for my bike. He got the bike running. The bike was running well for a few months. I went to start it up one day and it seemed to have a misfire. I checked for spark and all was good. I just checked to make sure the plugs would fire when grounded against the head. They also shocked you when you would try to remove the plug caps from the plugs. I continued to ride the bike hoping it would go away, but it got worse. In low RMS's the bike would sputter in the lower RPM's. Once it got above 2.5k RPM's it would act normal. It eventually got to the point where it would stall at stops, and the sputtering became unmanageable. I have a knowledgeable background in automotive. I went to automotive school for a few years, so I know a thing or two. I decided to give in, and give a shop a go at it. As luck had it, no shop wanted to take it on. I figured I would do it myself. I pulled apart the carbs and completely cleaned and rebuilt them. I followed all the steps on Bascliff's website, including chem-dip, bench sync, and tested the floats. I put them back together and got the bike running. The bike fires right up every time. It takes a little to get it going, but it starts, idles, and when in neutral rev like normal. When I take it on the road, it does the same thing! I really don't think the carbs are the issue. I started to look at the ignition again. I think something weird is going on. I have searched for over a week, and I cannot come up with anyone who has had the same issue, or any values for that matter. I am not the best at searching, but I have tried. Below I will list my testing of the ignition system along with my findings and questions.

Resistance Checks:

Signal Generator
Brn-B/W 70.6 Ohms
Grn/W-B/W 70.6 Ohms

Primary Wires
Right side Coil
O/W-B/Y 4.2 Ohms

Left side coil
O/W-W 4.2 Ohms

Secondary Wires
No matter what I do I cannot get any sort of reading from the secondary wires. All plugs are firing, but I cannot get a resistance value when I check the wires. I have pulled them apart, and cleaned them to no avail.

Voltage Checks:

Key - On Kill Switch - Run ALL CONECTIONS ARE CONECTED
BATTERY VOLTAGE 12.6V

Right side coil @ harness connection
O/W - 11.1 V - both sides of the connector
B/Y - 1.15 V - both sides of the connector

Left side coil @ harness connection
O/W - 11.01 V - both sides of the connector
W - 11.01 V - both sides of the connector

Igniter
O/W - 10.94 V
B/Y - 1.15 V
W - 10.94 V

Signal Generator
Gn/W - 47.5 mV when plugged in / 2.8-5 mV when unplugged (component side)
Brn - 47.3 mV when plugged in / 2.8-5 mV when unplugged (component side)
B/Blu - 4.6-5 mV when plugged in or unplugged
(sig gen wires from component are back with white. Wire after connector is black with blue)

Key - On Kill Switch - While Cranking ALL CONECTIONS ARE CONECTED

Right side coil @ harness connection
O/W - 9 V - both sides of the connector
B/Y - 4.5 V - both sides of the connector

Left side coil @ harness connection
O/W - 9.14 V - both sides of the connector
W - 4.5-5 V - both sides of the connector

Igniter
O/W - 9.14 V
B/Y - 3.3 V
W - Varies 4.3 - 6 V

Signal Generator (I held in the starter for about 10 seconds for each test)
Gn/W - Sporadic -(negative)30 mV to 30 mV
Brn - Sporadic -(negative)30 mV to 30 mV
B/Blu - (negative)48-(negative)50 mV

Here is the weird part.
When I was testing voltage at the coils and the igniter, the B/Y wire with 1.15 volts would jump to the W wire. After cranking, the B/Y wire would have 10.5 V and the W wire would have the 1.15 V. The only way to get the 1.15 V back to the B/Y wire would be to flip the kill switch off back to on. This jump would happen only sometimes, its intermittent. I am almost certain something is going on with my ignition system, but I do not know what. I know that battery voltage should be present at the coils, but I know its common with the old bike to have voltage drop. I want to figure this out. I am determined to get this back on the road. This is my first bike and I don't want to give up. I just need some help. if you see errors with my tests please let me know. I will try to correct or clear anything up.

 

[tom203]

Oh no, not another ignitor problem

econdary Wires
No matter what I do I cannot get any sort of reading from the secondary wires. All plugs are firing, but I cannot get a resistance value when I check the wires. I have pulled them apart, and cleaned them to no avail.

unscrew spark plug caps from the ignition coil plug wires. With your multimeter scale on 20k ohms, stick one meter probe into plug wire,other probe into other plug wire - you should see a reading of around 12 kohms. The plug caps get corroded and give you false readings: before reinstalling plug caps, cut back plug wires about 3/8 inch to expose fresh copper.

lots of ignitor problems with the gs550s - fortunately, you have the dyna s option to replace the stock suzuki setup
Note you need to determine whether you have a ND or KD ignition

https://www.z1enterprises.com/dyna-s-ignition-ds3-2-gs-fours-w-nd-ignition.html

 

[RRhoads]

Tom, thanks for your help. Can you tell me why it would be the igniter? What in my test results tells you the igniter is bad? I am trying to understand what going on that is causing the issues. I will try the sugestion with the secondary wires.

I am not sure how to determine if I have the ND or KD ignition. The sticker on the igniter has rubbed most of the way off.

 

[tom203]

Make sure your mechanical timing advancer moves freely: make sure that you have good electrical connections between ignition parts.
I don't know that the ignitor is the problem here. Understand that the ignitor is doing the same thing that a set of contact points would do - breaking the connection to the ignition coils based on a small signal. If you have an inconsistent spark, and your connections seem fine, the ignitor could be the problem. Testing them is inconclusive : best to get/borrow a known good unit and see if your issue goes away.
Cut back those spark plug wires.

the signal coil mounting plate might have a small "nd" scribed on it, if it's a ND ignition setup

 

[RRhoads]

Make sure your mechanical timing advancer moves freely: make sure that you have good electrical connections between ignition parts.
I don't know that the ignitor is the problem here. Understand that the ignitor is doing the same thing that a set of contact points would do - breaking the connection to the ignition coils based on a small signal. If you have an inconsistent spark, and your connections seem fine, the ignitor could be the problem. Testing them is inconclusive : best to get/borrow a known good unit and see if your issue goes away.
Cut back those spark plug wires.

the signal coil mounting plate might have a small "nd" scribed on it, if it's a ND ignition setup

Tom, I will try cutting back the wires. Just to be clear on checking the resistance of the wires. I will cut back the wires to expose fresh wire. I will measure resistance across wire for cylinder 1 and cylinder 4 for the right side coil. For the left side coil i will measure across 2 and 3. Are there any diagrams showing the build of the wires? when I pull the plugs apart, 2 and 3 have a spring, a white cylinder (seems to be a ceramic insulator), and the plug cap. Wires 1 and 4 have the "ceramic insulator" and the cap. The insulators are fairly dirty, and do not seem to have continuity. I have pictures if you would like to see them.

I just don't understand why B/Y is showing 1.15 V. I also don't understand why it will jump to the W wire in

 

[Gorminrider]

UKjules here on forum had a somewhat similar issue....per ignition. carefully CHECK the signalcoil wires where they go into the motor case ...

failing that, I am not entirely convinced it is ignition, seeing as bike starts and runs at higher rpms.

 

[RRhoads]

Ok, so I got a reading of resistance on my secondary wires. I never pulled my plug wire caps off to do this. My readings are as follows;

Right coil: 15.68k Ohms
Left coil: 16.14k Ohms

Should the caps have continuity? I am not getting anything from the caps. When the caps are connected, I am not getting a reading (resistance or continuity). I never pulled the caps off when I was reading for resistance.

 

[tom203]

The ignition coils that I have tested all showed about 12 kohm this way, but yours are close. The plug caps have a resistor with contacts that corrode and give poor reading. Just replace the plug caps with ngk 5kohm units about $5 each to rule them out as a problem

 

[roeme]

No reading on secondary, but firing: I'd say you don't have continuity, and somewhere on (broken) path the high voltage is simply arcing over. That's something your multimeter can't do, hence the zero reading.

...Just read what you said about the caps. As tom said, replace them, before going further. They age and go bad, and from what you write, yours are long gone.

Edit: Caps should read 5 kΩ - except if you have spark plugs with an integrated resistor, then they should read like a regular wire.

Resistor must be in either the spark plug or cap, but not both.

 

[RRhoads]

No reading on secondary, but firing: I'd say you don't have continuity, and somewhere on (broken) path the high voltage is simply arcing over. That's something your multimeter can't do, hence the zero reading.

...Just read what you said about the caps. As tom said, replace them, before going further. They age and go bad, and from what you write, yours are long gone.

Edit: Caps should read 5 kΩ - except if you have spark plugs with an integrated resistor, then they should read like a regular wire.

Resistor must be in either the spark plug or cap, but not both.

Happy 4th of July everyone!!!

Sorry for the late update. Here is what I did last weekend;

I removed the resistors from all the caps, and replaced them with brass rods. I made it so the caps had continuity. They had really low resistance, but continuity. For the caps with the spring, I just put longer rods in. The bike ran better, but still has a slight hesitation. The hesitation is in the lower RPM's. It is better, but still present.

I am still unsure what is causing this issue. Has anyone actually made sense of the data? Are the values above correct? Can anyone verify the igniter and/or signal generator is working properly? I don't want to be a parts changer. I want to understand what is going on.

 

[tom203]

Did you check the mechanical timing advancer? I'd get 5kohm ngk plug caps- not sure how ignition would behave in long term with no resistance.

 

[RRhoads]

Did you check the mechanical timing advancer? I'd get 5kohm ngk plug caps- not sure how ignition would behave in long term with no resistance.

Tom, what am I looking for in the mechanical timing advance? The no resistance in the caps is only temporary. I am trying to diagnose this issue without just buying parts. I think the no resistance caps tell me that there is not enough power moving through the wires and caps. Can we say the igniter is bad based on the reading I am getting from the B/Y wire? Should I be getting battery voltage?

 

[tom203]

"The hesitation is in the lower RPM's. It is better, but still present."

at idle, timing advance is about 10 degrees btdc : then it progresses to 40 degrees btdc. Maybe yours is stuck, so grab its nose and see if it swings about 30 degrees and returns smoothly.

http://www.partsoutlaw.com/oemparts/a/suz/50d3f824f8700230d8b4ce6c/signal-generator