Loss of power - unusual coloring of catalytic converter?

dduelin said:

Update....I've put about 1300 miles on the bike since swapping the original coils out with a pair I bought and it has run perfectly since.

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Awesome!! Sounds like a fix to me.

dduelin said:

Like to know about the coils though.

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Sometimes with this stuff you never do get to find out exactly what is wrong with the part we change, but the odd time we have to rely on an extremely educated guess. Evidence/symptom based troubleshooting will always get you where you want to be....

Scooter said:

Dave, after further thought I decided to go and measure one of my spare coils. Both the primary and secondary coils are isolated from the laminated core so in retrospect, it shouldn't matter if the core is grounded to the frame or not. I will test this out later next week since I have to take off my mid-cowling anyway for some other issues and it would easy enough to see if the bike runs when the coils are removed from their mounting points. That schematic from the service manual that I referenced earlier (pg 20-7) is in error. There is no ground connection going to the coil in the main wiring diagram shown in the manual.

I have also seen that same corrosion on the old coil that I removed off of my bike last year...

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Yes, one shows a ground and one does not....... I am confused. Without a ground path there is no way the 12v low voltage circuit can be energized by the black/white supply wire and the high tension lead has no continuity to ground except across the air gap of the spark plug. I didn't think to check for continuity from the 12v connector to the mount bosses but I will do so. Is that what you did to determine it is isolated?

I'll bet that if the coil were isloated (not well grounded), it won't last long and the spark is weak (at best). There has to be a substantial return ground path, and I don't see that the small wires and spade connectors are sufficient.

dduelin said:

Yes, one shows a ground and one does not....... I am confused. Without a ground path there is no way the 12v low voltage circuit can be energized by the black/white supply wire...

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There has to be a path to ground on the primary side or the coil won't work. When the coil is not firing, there's DC flowing through the primary (ECM side) winding, which creates a magnetic field that does pretty much nothing on the secondary (spark plug side). When the ECM wants to fire the plug, it cuts power to the coil, causing the magnetic field to collapse. The motion of the field during that collapse induces a very high voltage on the secondary winding, enough that jumping the gap in the spark plug to find ground isn't a problem. (Older electronic ignitions and those that run on points work exactly the same way.)

You should find continuity (or some amount of resistance) between the mounting bolt hole and each of the primary lugs on the coil pack. The secondary side should be the same way, but you should find nothing in common with the primary side except ground, and even that's optional because they're both bolted into the frame.

--Mark

dduelin said:

I didn't think to check for continuity from the 12v connector to the mount bosses but I will do so. Is that what you did to determine it is isolated?

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Simple resistance measurement between the core and each terminal of the primary and secondary taps reveal a very high impedance (i.e. no reading) using my crusty old Fluke 77 multimeter. Primary coil resistance measures roughly 2.1 ohm, secondary coil measures 21.9k ohms.

Blrfl said:

There has to be a path to ground on the primary side or the coil won't work.

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Ground path is being provided by the ECU via the Blue/Yellow wire to coil bank 2-4, and the Yellow/Blue wire to coil bank 1-3. +12V is supplied via the Black/White wire from the Engine Stop Relay...

Blrfl said:

You should find continuity (or some amount of resistance) between the mounting bolt hole and each of the primary lugs on the coil pack. The secondary side should be the same way, but you should find nothing in common with the primary side except ground, and even that's optional because they're both bolted into the frame.
--Mark

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As I noted in my previous post I cannot measure any resistance between the mounting bolt holes (i.e. laminated core) and the primary or secondary windings of the coil with the coil removed from the bike.

I kind of suspected what Dave was asking about originally with the grounding of the mounting bolts of the coil because I have seen the same corrosion on one of my coils...

Ive 2 spares... I'll check mine tonite.

Scooter said:

Ground path is being provided by the ECU via the Blue/Yellow wire to coil bank 2-4, and the Yellow/Blue wire to coil bank 1-3. +12V is supplied via the Black/White wire from the Engine Stop Relay...

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And I just remembered that the 1300 fires both cylinders on a side at the same time. So that does make sense. Derp.

--Mark

Scooter said:

Simple resistance measurement between the core and each terminal of the primary and secondary taps reveal a very high impedance (i.e. no reading) using my crusty old Fluke 77 multimeter. Primary coil resistance measures roughly 2.1 ohm, secondary coil measures 21.9k ohms.

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BakerBoy said:

Ive 2 spares... I'll check mine tonite.

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As promised...

I measured from my two spare donor coils (extracted from a 2007 ST1300) to get the following readings:

• Coil with 1 & 3 cylinder markings:
• >>Primary: 2.3 ohm between spade connectors
• >>Secondary: 32.36k ohm between plug connectors
• Coil with 2 & 4 cylinder markings:
• >>Primary: 2.3 ohm between spade connectors
• >>Secondary: 32.92k ohm between plug connectors
• Between a single primary coil tap (either spade connector) and a single secondary coil tap (either plug connector): out of limits high resistance (open circuit)
• Between a single frame mounting hole (either hole) and any other primary or secondary coil tap (any of the spade or plug connectors): out of limits high resistance (open circuit)

I use a Radio Shack digial multimeter.

I experienced exactly what you did based off your description a few years ago on my Z1000. Randomly under throttle it would run like crap. I would kill the throttle switch while pulling in the clutch then would pop the clutch to restart while cruising. This would clear the poor running and misfiring for a little while. This continued on through a whole tank of gas. Once I dealt with this for 140 miles and refilled, problem never ever reappeared. Coils typically work or they don't. If you have a crack in the coil case or insulation issue on the spark plug wires, you should only be experiencing these symptoms in the rain. I have had my share of ignition related issues on older multiple cylinder Hondas and from this experience, it is very difficult to run with two dead cylinders if it could at all. In the automotive world, the most common failure of catalytic converters is due to misfires. The raw fuel melts the honeycomb catalyst. This is normally related to failed coil packs or clogged Egr ports. Curious to see if it reoccurs. Even the best gas stations have issues with contamination in the tanks. Especially when they make the switch to winter fuel and vice versa. Most common time for us to get random misfire codes.

Blrfl said:

And I just remembered that the 1300 fires both cylinders on a side at the same time. So that does make sense. Derp.

--Mark

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I believe the "fires both cylinders" is to complete the high voltage secondary circuit. No circuit grounding required and safer for a rider, same method as my '83 Shadow.
Verified by BakerBoy's secondary resistance to ground readings (infinite)

BB, I bet you measured the secondary coil resistance with the plug wires attached. I took off the wires for my measurements although it made it more difficult to reach into the deeper well for that one contact point...

Scott, yes, measurements were with plug wires still attached.

BakerBoy said:

Scott, yes, measurements were with plug wires still attached.

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I just stick my finger in the spark plug socket. If I scream and wet myself I consider the coil good.

dr1954 said:

If I scream and wet myself...

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Booger says this is quite common...

dr1954 said:

I just stick my finger in the spark plug socket. If I scream and wet myself I consider the coil good.

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Lick it first, or not? opcorn

Hello - a very similar occurrence happened to my 2007 ST about 3 years ago. We were on our way home when the bike suddenly lost power. By cranking the throttle we managed to make it to a phone booth. We had run that way for about 2 miles. The RH muffler was a dark blue/bronze. I had lost power to both RH cylinders. When the mechanics checked it there was a feed wire to the LH coil that had broken off under the plastic shield. They replaced the connector and all was OK. As for the muffler - the catalytic converter sounded like it had fell apart inside the muffler body and I had it replaced under warranty.

Scooter said:

Booger says this is quite common...

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So that is why you camped at the farm instead of rooming with us at Moonshine?

BakerBoy said:

Lick it first, or not?

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Nope, just make sure I am grounded.

Bill144 said:

We were on our way home when the bike suddenly lost power. By cranking the throttle we managed to make it to a phone booth..

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A phone booth? I don't think my bike even has enough gas to run that far with all four cylinders firing.