Arggggh!! Running on 3 cylinders ?!? Video included

Ugh. 2 steps forward and 4 steps back. It seems I'm fighting one thing or another.
Quick Recent History:
* Picked up bike, great mileage (40+) for a while
* Pulled plugs (stock per manual) - look great !
* Weeks and weeks later, mileage dropping, got worse over time.
* Checked air filter, four-way vacuum ... all other hose connections
* Reset the CPU (jumpered plug under seat) recently
* Changed the oil (Shell Rotella T Diesel + filter)
* Mileage improved dramatically ! (from ~200 miles a tank to most recent almost 300).
* Last 2 days, performance going downhill fast - most recent tank fill - almost 70 miles and about 1/2 tank now.
* Removed plugs last night - look great ! (37,000 miles now)
* After re-installing plugs, fired bike up and took timing light pickup to each spark plug wire - light output (though right-rear cylinder seemed "not as strong").

If I'm sitting at a red light, and take off as you should, she coughs and spits ... if I bring the R's to about 2,000, and pull away slowly, she's fine.
I've heard her back-fire 2-3 times in the course of the last couple of days.

I run name-brand fuel,
I smell un-burned fuel out the back, even though timing light shows firing (borked plug?)
I plan to sync the throttle bodies this weekend - not sure that's it
Bad \ faulty injector?
Bad sensor?

Okay, here's the video to put this into some perspective (the "loud noise" you hear before startup is the radiator fan - sorry):
Notice when i blip the throttle, the idle bumps up too (that's not me holding the idle up).
Watch out for the spider !!

[video=youtube_share;P0CuoT8W3Dg]http://youtu.be/P0CuoT8W3Dg[/video]

Check valve clearances.

Have you checked the coils?

When you sync the carbs clean out all the hoses and the 5-way T. Make sure the map sensor opening is clear. I think you have a plugged line.

Change your plugs. Plugs are good for 16,000 miles, not 37,000 miles. The corners of the plug wear down and the spark has to jump too far to ignite properly.

Please give us an update.

georgeorge said:

Check valve clearances.

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Considering the mileage, and not knowing the history, I will check their clearances - thanks!

Mellow said:

Have you checked the coils?

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Nope, haven't checked the coils - I'll check with the Service Manual to see the measurements tolerated ...

Justytroll said:

When you sync the carbs clean out all the hoses and the 5-way T. Make sure the map sensor opening is clear. I think you have a plugged line.

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About 2 weeks ago, I did check the 5-way, although I did not check the hoses. The 5-way looked brand new - no debris inside (running a q-tip through came out clean).
Haven't checked the map sensor, but will do so!

RCS said:

Change your plugs. Plugs are good for 16,000 miles, not 37,000 miles. The corners of the plug wear down and the spark has to jump too far to ignite properly.

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I never meant to imply that these are the original plugs (although the P.O. declared they were changed at 30k).
When I pulled them last night, they had that almost "perfect" look, which seams counter to how it's running.
Still, I shall change the plugs (just to eliminate that possibility), in addition to the other suggestions.

I also plan to change out the fuel filter.

One interesting side note ... when I recently checked the 5-way and all looked fine ... she still ran not up to par, so I reset the CPU (thinking, 'what the heck') and she was instantly transformed to how you would expect an ST to run.
But over the last couple of weeks, she's been degrading to where we are today

Thanks for the all the suggestions and I will check \ replace each ...

I can't hear that it is running on 3...sounds normal to me (including the idle rpm change after blip ping the throttle).

Do you have a handheld IR temperature gun? Check all 4 exhaust header temperatures frequently, from a cold startup.

BakerBoy said:

I can't hear that it is running on 3...sounds normal to me (including the idle rpm change after blip ping the throttle).

Do you have a handheld IR temperature gun? Check all 4 exhaust header temperatures frequently, from a cold startup.

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Forgot about that trick (as I've done with my cars) ...
measurement taken at exhaust tube, about an inch below head

Before startup
-Left bank-+-R.Bank-----
F. 88 | 93
R. 88 | 94
-- before muffler ----
80 | 80

One bar showing on temp gauge
-Left bank-+--R.Bank-----
F. 148 | 163
R. 130 | 157
-- before muffler ----
113 | 103

Two bars on temp gauage
--Left bank-+-R.Bank-----
F. 141 | 180
R. 147 | 177
-- before muffler ----
147 135

3 bars on temp gauge
--Left bank-+-R.Bank-----
F. 151 | 186
R. 136 | 185
-- before muffler ----
148 | 138

3 bars on temp gauge ...
measurement taken at head, just above exhaust tube
-Left bank--+-R.Bank-----
F. 154 | 190
R. 137 | 177
- before muffler --
145 | 137

Hmmmmmmmmmm.

Left bank, rear cylinder may not be firing as much as the others... throttle body sync may help balance that.

caldercay said:

Nope, haven't checked the coils - I'll check with the Service Manual to see the measurements tolerated ...

I reset the CPU (thinking, 'what the heck') and she was instantly transformed to how you would expect an ST to run.
But over the last couple of weeks, she's been degrading to where we are today

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Ignition related problems can be very dynamic and not show up on a coil resistance check, but it doesn't hurt to do it anyway in case they're just generally weak. the optimum diagnosis is to put the engine on a scope and observe the ignition pulses in real time as you vary the engine speed (preferably on a dyno where you can also load the engine and drivetrain if the problem seems to be load related). not something the average home mechanic has on hand, but the right tool for the job if you can't diagnose the problem via other means.

Also, if its easy to reset the CPU, why not do that again and see if it produces the same result as last time. If so, that may answer your question.

caldercay said:

Forgot about that trick (as I've done with my cars) ...
measurement taken at exhaust tube, about an inch below head

Before startup
-Left bank-+-R.Bank-----
F. 88 | 93
R. 88 | 94
-- before muffler ----
80 | 80

One bar showing on temp gauge
-Left bank-+--R.Bank-----
F. 148 | 163
R. 130 | 157
-- before muffler ----
113 | 103

Two bars on temp gauage
--Left bank-+-R.Bank-----
F. 141 | 180
R. 147 | 177
-- before muffler ----
147 135

3 bars on temp gauge
--Left bank-+-R.Bank-----
F. 151 | 186
R. 136 | 185
-- before muffler ----
148 | 138

3 bars on temp gauge ...
measurement taken at head, just above exhaust tube
-Left bank--+-R.Bank-----
F. 154 | 190
R. 137 | 177
- before muffler --
145 | 137

Hmmmmmmmmmm.

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Great information. I am guessing here. If the previous owner said he changed the spark plugs at 30,000 miles I am going to bet he never checked the valve clearances. I have done several valve clearance checks and shim changes and what I have learned is that the exhaust clearances tend to close on the ST1300. Tight clearances on the exhaust valves may cause a few cylinders to heat up more than the others. As I understand it, a tight exhaust valve clearance will not allow the valve to close correctly so it can transfer heat of the combustion to the head. Your right front cylinder may have the smallest exhaust valve clearance.

Once you do the basic maintenance - valve clearance check, spark plug change see how it runs. It should run fine. If not, the things I would check next are the spark plug wires and then very last the fuel pump motor.

jfheath said:

Check the htleads at both ends. It unscrews from the plug cap and has about an inch of lead buried in the plug cap itself. Look for verdigris - green corrosion. It is a push fit into the coil body, should push onto the pin and be held in place by the screw cap pressing against the gland which is stuck firmly onto the lead.

The plug cap should have a resistance of 5k ohms. 4.5 or 5.5 i know indicates a fault.

Info and pics from a problem i had here

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Great write-up on your past issue, John... imagine my bike exhibiting similar characteristics and we both show #3 issue !

I have noticed that the front cylinder HT leads are much longer and allow easier removal from spark plug bore, whereas the rears have barely enough length to allow the lead to come out of the spark plug bore.

living in a mild dry climate I hadn't thought of corrosion on the HT leads, that would be great if it turned out to be something as simple as that. Still wondering why resetting the CPU was a temporary fix, because that wouldn't have done anything to remedy any other issues, but maybe it was just a coincidence that the problem temporarily went away at that particular time.

dwalby said:

living in a mild dry climate I hadn't thought of corrosion on the HT leads, that would be great if it turned out to be something as simple as that. Still wondering why resetting the CPU was a temporary fix, because that wouldn't have done anything to remedy any other issues, but maybe it was just a coincidence that the problem temporarily went away at that particular time.

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The previous day I had lifted the tank and removed the airbox, removed the 5-way and checked it out (ran a q-tip in the 5-way - spotless!).
Maybe my big fat hands jingled something around during removal \ installation of airbox? (I did nothing explicitly with the coils\HT wires).

Maybe it's coincidence I inadvertently jiggled something, bolted the tank down, then was thinking, "maybe I should reset the CPU?" and did so?

Certainly a quick test would be for me to do a[nother] reset and go get some lunch and see how she runs.

Email sent....standing by the white courtesy phone if needed.

That rubber donut is heat welded to the lead. Don't think there is a glue that will work. They should make both ends screw on.

This brings up that inline resistor in every plug cap. Why is it there??? I've removed them in every bike I've owned. Got to give a hotter spark.

Since there are 2 resistors in the circuit that's 10k ohms resistance removed. Wish I could get non resistor plugs in the iridium type.

Pete in PA said:

That rubber donut is heat welded to the lead. Don't think there is a glue that will work. They should make both ends screw on.

This brings up that inline resistor in every plug cap. Why is it there??? I've removed them in every bike I've owned. Got to give a hotter spark.

Since there are 2 resistors in the circuit that's 10k ohms resistance removed. Wish I could get non resistor plugs in the iridium type.

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Radio noise interference reduction.

Igofar said:

Email sent....standing by the white courtesy phone if needed.

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Just hung up with Larry ... he's given me a number of homework assignments.
Talk about someone who can instill confidence in getting the STead back on the tarmac !

FWIW ... the ECU reset today didn't work (obviously a coincidence).
Jumped on the CBR to Honda and picked up some new purty NGK plugs.

I'll do the plugs tonight, then replace the TB vacuum lines and do a TB sync this Saturday (gotta do a carb sync on the CBR too).

[OT]I've also been assigned to flush\fill the rear pre-load (as the knob can go 20 clicks w\o resistance)[/OT]
[OT]2nd off-topic assignment ... replace the driven flange bearings ... I mentioned the bike feels like the front end is sliding on ice, so ...[/OT]

I *will* double-check everything as suggested by everyone ... that way I will *know* in my own mind all is good or needs adjustment.

I'll report back progress so that others lurking (or whatnot) can benefit from my [-]misfortunes[/-] challenges.

Also make sure the crank sensor plug is fully connected.

RCS said:

Also make sure the crank sensor plug is fully connected.

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Thanks Bob ... will do!

I've got all the tupperware off, so I'm gonna check all that makes sense ... plus it will give me a chance to check on other things.