Ignition Problem?

Mandrake said:

I recently relocated my coils from their stock locations to under the tank. This involved building longer plug wires and a bracket to bolt the coils to. On my first ride, my bike would do exactly what you're experiencing, but only when hitting a hard bump, and with the addition of the CEL coming on for a few seconds. It was bump dependent, not RPM/ throttle position dependent. Turns out, my coils were momentarily losing ground. Bracket fixed, no more issue. You might want to look at how the coils are grounding to the frame.

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Thanks Mandrake, yeah, this was one of my first suspicions so I removed and cleaned the mounting points for both coils. The surfaces looked nice and clean and the bolts were tight and performing that cleaning made no difference. I've also tested the coils with a multimeter and found them to be seemingly fine. I cannot replicate the condition in the garage as there's no way to achieve 4250 RPM with the throttle closed. Is anyone parting out an ST1300? I'd love to swap out the ECM for a quick test.

wjbertrand said:

first were there outward signs of the abrasion visible on the harness before stripping it back like that first photo?

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I don't recall, however something must have piqued my interest to open up the wiring harness. I may have been revisiting an earlier modification of the wiring harness, so anything out of the ordinary would have caught my attention.

wjbertrand said:

Second, did repairing those wires solve your problem?

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Absolutely!

There is a local wrecker close to me who just advertised a wrecked 2003. I am following along gaining knowledge along the way and awaiting the resolve.

wjbertrand said:

I cannot replicate the condition in the garage as there's no way to achieve 4250 RPM with the throttle closed.

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Sounds like a good excuse to add a dyno to the garage. Can't recall what you've done with the ECM so far, have you completely removed the power from it, I assume you probably have. The reason I ask is you may have had some kind of software glitch that a complete power removal reboot might clear up.

dwalby said:

Sounds like a good excuse to add a dyno to the garage. Can't recall what you've done with the ECM so far, have you completely removed the power from it, I assume you probably have. The reason I ask is you may have had some kind of software glitch that a complete power removal reboot might clear up.

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Yeah, I had the ECM completely out of the bike and on my bench. I examined all the connectors under an illuminated magnifier. Everything looked brand new, those connectors have weather tight seals on them. Same for the harness plugs. I cleaned everything off with plastic safe contact cleaner anyway, reassembled and test rode it, alas no change. Last night on the way home from work I deliberately ran the bike at the troublesome RPM and throttle setting, which provoked a lot bucking and jerking, hoping to force an error code. Unfortunately the diagnostic test shows no codes in the memory.


-Jeff

Update. Eliminated 3 more possibilities: I performed a TPS test, by back probing the connector with the key on. Getting 5.5V where I'm supposed to, ground where I'm supposed to and the ~0.44 to ~4.6V from throttle closed to wide open is exactly what it's supposed to be. Rotating the throttle very slowly from fully closed to fully open gives an extremely smooth response on my analog meter. I even tried tapping on it whilst I changed the throttle position. It's not the TPS.

Next Hal came over and we swapped ECMs. The problem follows the bike, not the ECM. Hal's bike runs fine with my ECM and mine still stutters with Hal's ECM. It's not the ECM.

This morning I tried by-passing the side stand switch. That made no difference and I validated that my jumper stayed in place by lowering the side strand at the end of the test with the bike still in gear, which when not bypassed, should stall the engine. The engine remained running. It's not the side stand switch.

I had Hal run the engine, moving the throttle back and forth around 4250 RPM while I held my hands near the exhausts, I can feel and hear both banks stuttering in sync with the tachometer dipping. Whatever is wrong I believe is affecting all four cylinders.

I went to examine the clutch switch and the connector lug broke off when I tried to remove the wire. It's pretty corroded and due to the broken lug, now needs replaced anyway. Not sure if a dicey clutch switch could cause this problem.

Jeff, in post 36 you stated you tested the coils, but didn't specify how, are you talking about a simple static resistance test on the two coils? I'm not sure that's going to be conclusive enough to rule out a dynamic issue. Before you were claiming that the problem only occurs when coasting with the throttle closed @4250, but accelerating @4250 its not present. Your latest comment about Hal modulating the RPM in the garage with you feeling the exhaust suggests its 4250 RPM dependent and not necessarily throttle+RPM dependent. Did I hear you correctly? That sounds like it could be a possible coil issue, I'd swap the coils/wires with Hal's bike and see what that tells you, it will at least rule those two variables out if nothing else. If the problem goes away, then swap either wires or coils back to see if either or both are the cause. In fact, I'd pull all the coil wires out of the coils and spark plug boots and inspect them on both ends, you could have corrosion in there that's contributing to the problem.

Thanks Doug, the throttle has to be closed or nearly closed. It does buck on the road if I try to go from closed to open throttle at that RPM. I previously couldn't reproduce it in the garage but with some subtle finessing of the throttle around 4250 I was able to get it to sputter. I checked the coils for static resistance with a meter and made sure the ground was solid. I also took the HT wires off and inspected/cleaned the sockets they sit in on the coils. I also made sure all the spark plug leads were firmly seated. Not sure how else to check them. The problem is not simply RPM alone dependent because I can accelerate cleanly through that RPM with the throttle more open, as smooth as you like. Another observation is that it doesn't act up for the first 5 minutes or so, even though the temperature, according to the gauge at least, is fully up to three bars.


-Jeff

Swap coils with the other bike?

wjbertrand said:

I went to examine the clutch switch and the connector lug broke off when I tried to remove the wire. It's pretty corroded and due to the broken lug, now needs replaced anyway. Not sure if a dicey clutch switch could cause this problem.

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It would be easy enough to run down. Disconnect the clutch switch and test it. Then reconnect that, disconnect the sidestand switch and repeat. Then do the same with the neutral switch. If the test fails (it hiccups at 4250), whatever switch was disconnected is at fault.The only switch that would likely cause this while you're underway is the sidestand switch. That switch is closed when the sidestand is down, so disconnecting it will force the bike to think it's up.

--Mark

wjbertrand said:

Not sure how else to check them.

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I'd swap them with Hal's bike. Its easy, you haven't tried it yet, and the symptoms you're experiencing are at least consistent with coil malfunction. If they're failing within a 50 RPM range and specific throttle opening, I wouldn't put too much faith in the static checks you've performed on them.

Blrfl said:

It would be easy enough to run down. Disconnect the clutch switch and test it. Then reconnect that, disconnect the sidestand switch and repeat. Then do the same with the neutral switch. If the test fails (it hiccups at 4250), whatever switch was disconnected is at fault.The only switch that would likely cause this while you're underway is the sidestand switch. That switch is closed when the sidestand is down, so disconnecting it will force the bike to think it's up.

--Mark

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Nope, it's just the opposite, closed when up (retracted), open when down.

wjbertrand said:

Nope, it's just the opposite, closed when up (retracted), open when down.

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Odd. My service manual says "Continuity should exist only when the sidestand is lowered."

But that being the case, the sidestand switch should be suspect as well. Bypass it and see if the problem goes away.

--Mark

Down is open according to the wiring schematic. Which kinda makes sense so it fails safe err assuming safe means not driving it off the side stand .
22-28 verbiage of my 03-07 service manual appears to be wrong.

Confirmed, continuity with side stand up at green connector.

Added that to the list of corrections.

--Mark

Blrfl said:

But that being the case, the sidestand switch should be suspect as well. Bypass it and see if the problem goes away.

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He already has done that bypass test, with no improvement.

Thanks, going to have another session with the bike this weekend and I'll check this out. Hadn't too seriously considers the plugs or wires as my experience is that problems with those usually show up under high load conditions.


-Jeff

OK, I changed the plugs this weekend (they had 50K miles on them but were the iridium variety) They looked fine and the new plugs made no difference it the way the bike runs. I tried to see how to remove the plug caps from the wires but they appear molded in. There's a little resistor that I was able to remove taking a flat blade screwdriver tor remove the retainer thingy, but I couldn't see how to remove the cap from the wire. As the bike runs strong on full throttle load, even at the troublesome RPM, I'm doubting it's a plug / coil problem.

jfheath said:

On my 2006 St1300, the leads and caps were separate items.

Post #13 at this thread link has pics showing the two items. It was a tight screw fit - the lead screwing in about one inch to get to full depth. They may be perfectly ok, of course, but then, i thought mine were.... ! The resistance test of the lead and cap may give an indication.

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Thanks for that John, when I was looking at mine I couldn't tell if the cap was molded over the wire or not and I was reluctant to twist it.

wjbertrand said:

Thanks for that John, when I was looking at mine I couldn't tell if the cap was molded over the wire or not and I was reluctant to twist it.

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If it helps I do have a spare coil from my 08 that I switched out trying to figure out a strange idling issue I was having at the time that just went away, the coil change didn't make any difference in my case but you are welcome to it to try out, shoot me your address in a PM and I'll mail it off.