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Discussion Starter #1 (Edited)
Dang it! 2300 miles on the '05 ST4S... never a hiccup or anything... first day in the high 70f range... out with wifey, slapping the bike around on some nearby twisties... and then after an hour of spirited riding, I pull up to a stop sign out in the boonies, and it dies.

Red light on the dash. I hit the starter button, and it cranks and sputters. I open the throttle a bit while it's cranking and it fires, but as soon as I close the throttle, it dies again. After starting again, it seems to run fine, but it's like the idle screw backed out, because it won't even try to idle.

Because I had wifey along, and we were miles away from civilization, I wasn't about to raise the tank and play with it, so I used the fast-idle lever to set the idle speed to around 1500rpm (the lowest I could set it before the fast-idle would slide back off) and continued the ride.

The bike ran completely fine, and I was really working the engine with 2up and twisties happenin' - so we went for about 2 more hours of fun. Then, as the air started cooling down, I decided to try flipping the fast-idle back off and see what it would do. It idled, but at around 1000rpm. Then at the next stop sign a few minutes later, it died again... and wouldn't idle.

I used the fast-idle 'til we got home and in the driveway, I raised the tank to look at the idle stop-screw. The factory paint was still on the screw, so I know it didn't move. The factory paint on the screw cracked as I cranked the screw in... and it had to do about 1.5 - 2 turns to idle properly at about 1200rpm. Then the idle didn't falter at all, so I ripped it out to the freeway, whacked the throttle a few times, did a few wheelies, and brought it back to the driveway. The idle stayed right at about 1200, solid as a rock.

I haven't played with it since, and I'm wondering WTH could have caused this?

I checked for positive/negative pressure in the tank, there was none. I'd think it could be bad gas, but it runs perfectly, and now idles perfectly with the new setting.

Any ideas?

Thanks.


:)
 

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If it is your first trip out after the winter layup, have you looked at your battery? Many unusual things happen due to the battery being at the end of its span.

It would be unusual to have the engine run fine, then not and crank the idle screw 2 turns. That is a huge amount and suggests that the idle screw is not the issue. I would put it back to stock and look for other problems.

Dave Harhay
 

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You should look for other problems just in case.
Especially the battery as dharhay said. Weak battery could cause all sorts of problems including low voltage to the fuel pump especially at low RPMS.
The fuel pump itself could also be an issue. Best to get them checked out and see if they are running at correct outputs.
Other potential issues fuel filter-pinched hoses
 

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Discussion Starter #4
Thanks guys.

Battery is new with the bike, connections are tight, and sitting voltage is over 13.1 - I think it's okay. I've been riding it all winter.

And thanks for the heads up on the fuel pump, I give it a look... but if that was the problem, wouldn't it be more symptomatic at higher throttle settings, rather than idling?

Does the TPS have anything to do with idle?

Thanks again.

I hate to go to the shop for a warranty claim, because they're starting to get REALLY busy this time of year... and the R1 is still mothballed in the basement with water in the radiator.


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How long did the bike sit? I've seen similar symptoms from gas that's been sitting. Even if it doesn't smell like paint thinner gas can get "stale" remarkably fast. If you haven't already, try a fresh tank of fuel.

I do wish we had an easy idle adjustment like Aprilia's handy little knob, though.
 

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Things that come to mind are a little water in the fuel,
Air sensor
Pressure sensor
These two will tell the ECM what AFR map to run at for the current conditions

TPS, although I think this would have to way off to cause problems.

Throttle syncing, this is what I would look for first if after the fuel issue was not a problem.
One of the throttle plates could be closing just a tad to much.

Unfortunately, if you don't have allot of tools for bikes, like software tools, and synchronizer tubes and such, it's difficult to diagnose well.
You can only look for the obvious things like loose wires or bad connections, etc.

good luck
 

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Discussion Starter #7
Thanks for the ideas. I'll try new fuel and *listen* to the fuel pump tonight.

I'm curious to how it's going to run after sitting a couple of days.

OBTW - when I rebuilt the fuel filler door, I used BelRay Waterproof grease to make the action smooth on the lock mechanism... I wouldn't think it would be significant in a full tank of fuel... but... ???

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Check your plugs.

I would check your plugs. I had a problem with my plug fouling out. They were black and the bike wouldn't idle. I put a new set in and she fired right up. obviously it was running too rich so I had the dealer adjust it for me since it was still under warrenty. I may be wrong but it may just be as simple as that.
 

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Discussion Starter #9
Well, I didn't check the plugs because it seems to run totally fine. I cycled the fuel pump several times, and it sounds robust as ever.

The bike seems to run perfectly. Idling perfectly at the new setting. The bike smells a little rich, but probably just because it was running in the garage.

I'm really at a loss on this one. The bike runs perfectly for 2300 miles at one idle setting, and then, instantly, the idle screw has to be turned in a bunch, and then it's idling perfectly at the new setting.

The last thing I'm wondering, is there a splined shaft on the actuator with the idle screw, and did the actuator just settle into the spines, which would probably mean my TBSynch is now FUBAR, right?

Guess I'm wavin' the white flag on this one... time to let Ducati pay for some of the guesswork.

Time to pull the R1 out of the basement... was afraid I'd need to use that thing sometime. ;)


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Discussion Starter #10
Last update: (I hope)

The tech went over the bike with the computer, and confirmed that something must have settled... and when it did, it knocked everything a little out of adjustment. He said the TPS was off, and the TBsynch. My CO was running a bit high, too.

No charge for the adjustments (of course)... and 2 hours later I was on my merry way.

Hopefully, my next visits to the shop will only be at 6000 mile intervals.


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That sounds about right. My sync was off early at 600 miles. I reset it then and it stayed good even after 8000 miles latter so hopefully yours will be good for a long time.
 

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Discussion Starter #12
UPDATE:

It's doing it again. This time, it kept idling, but at about 800 RPMs... sounded like it was going to die, but kept running, barely.

It's definitely weather related.

I rode the bike 1500 miles last weekend, almost all of it aggressively ridden Arkansas and Missouri Ozarks roads... the Diablo Strada is toast at 1700 miles... and the only time the idle speed was acting up, was when the temperature reached the mid 80s with lots of humidity. Later, when the temps cooled and the weather was drier, the bike idled fine.

Any more ideas? Thanks.


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On my SS there is a temperature sensor mounted on the triple clamp in back of the head light. It can get dirty or covered w/ bugs which can screw up the reading.
 

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Discussion Starter #14
Thanks, I'll have a look. It does act as if it could be over-richening at idle. (?)



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Discussion Starter #15
Well... it's doing it again. Sputtered and died at a downtown intersection.

I don't really feel like taking it back to my dealer... he can't figure it out either.

Oh well.


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Check your gas tank.....my ST2 did exactly the same thing. Seems that the little "ears" on the bottom rear edge of the tank harbor any water that gets into the tank. As we ride, the water starts sloshing around with the fuel, and some of it emulsifies with the gas: the gas/water emulsion is heavier than gas and lighter than fuel, so it's getting picked up and run through the system, and the water is retained in the in-tank filter, ruining the petroleum-only filter and causing a drop in fuel pressure.

I drained my tank, and about 4 ozs of water came out; I replaced the fuel filter, buttoned her back up, and resolved to buy fuel from busy gas stations only. Haven't had a problem since.

Edit>>> to see if you have water in the tank, take one of the cheap kerosene hand siphons (the clear type with the orange plastic hand pumps on top) and jam it down and back towards the bottom left rear side of the tank, as far as it will go, and give a couple of squeezes to the bulb: if you suck up brown nasty stuff, you've got a water problem. This can save you from having to spend 7 bucks on a new bottom gasket on your tank/pump assembly.

If you have no crud in the tank, check your idle speed fuel pressure...you may not have water in the tank, but some may have buggered your fuel filter.
 

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Discussion Starter #17
Thanks, I'll look into that... but it ONLY happens when it's hot and humid.

It runs and idles perfectly at all other times.



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