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Discussion Starter #1
I have an '06 ST3 with a dual spark engine. Last year it was running a bit rough around 5,000 to 6,000 rpm...found that the right horizontal plug was not firing. Replaced the unit and all was fine. 2,600 miles later it died again! Replaced the unit and all is well again. The plug was wet and had chunky black soot (the left plug from the same cylinder looked normal, the soot was a bit black, so I'm running a bit rich).

Something is amiss.

Do you think that a weak spark could lead to fouling and eventual failure of a plug?

Could this be from a plug wire that is degrading?

The coil for the horizontal cylinder has two leads. Are the leads independent or do they both work simultaneously from the same circuit? :think:

I'm stumped at the moment. Anyone out there have a suggestion?

Thanks!!
 
J

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Could be coil or spark plug wire. Check for any faults on the coils w/ a DDS tester. Check the gap and thermal rating or incorrect thread length.
 

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Assuming the plug wires are okay: Is the plug wire being fitted all the way on? The belt covers have a way of interfering with the fit IMO, ie the right side wire end caps do not give that nice "click" feel when the wire cap is on all the way like on the left side plug wires. Maybe it is backing off if not fitted all the way. Is the wire "clenched" between the battery box and the belt cover? If the plug isn't firing, it will foul.
 

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Could be coil or spark plug wire. Check for any faults on the coils w/ a DDS tester. Check the gap and thermal rating or incorrect thread length.
My money is on a coil going bad. Look for cracks or arc burns.
 

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Discussion Starter #5
Okay...I think I have a plan of attack.

The plug cap has been fitting well. I get a solid connection and there is no sign of arching in the boot. The coil looks good from the outside...no clear indication of cracks or arcing. The plugs are of the correct size and gap...so good to go there. I'll do a compression test (easy enough and I'm right there anyway) then switch the leads at the coil...see if the other plug now becomes fouled. If that's the case...new wires. If not...new coils (and, of course, new wires...they tell me it's only money :rolleyes:). Since both scenarios call for new wires, I might as well start there!

Thanks for the suggestions! I'll keep you posted...but this will take some time.
 

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Life is too short to worry !
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If you are going to replace the leads then my recommendation is Magnecor (you can read the reason why on their website) with a switch to Iridium plugs she will leap into life and run smoother once you have sorted the existing issue you have.
 

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Discussion Starter #7
Thanks Gearbox...I was thinking of getting the Magnecor wires. I saw in LT's book that he recommends opening the gap wider when using iridium plugs. What gap do you use?
 

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Okay...I think I have a plan of attack.

The plug cap has been fitting well. I get a solid connection and there is no sign of arching in the boot. The coil looks good from the outside...no clear indication of cracks or arcing. The plugs are of the correct size and gap...so good to go there. I'll do a compression test (easy enough and I'm right there anyway) then switch the leads at the coil...see if the other plug now becomes fouled. If that's the case...new wires. If not...new coils (and, of course, new wires...they tell me it's only money :rolleyes:). Since both scenarios call for new wires, I might as well start there!

Thanks for the suggestions! I'll keep you posted...but this will take some time.

Coils go out only rarely. The only time I had a coil problem, not on my ST, the symptom was sputtering under acceleration and above a higher rpm. Oherwise the bike started and idled well and drove well below a certain rpm. The suggested reason the coils got weak was wrong fitting plugs under the plug wire cap, they needed that little screw on metal cap, ie the juice had to arc twice.
 

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Discussion Starter #10
Styder,

Yeah...I've never had a coil go bad on anything that I've owned yet. I have had wires fail (I'm hoping this is the case!!!!). This weekend I'll put some miles on with the coils switched. Let's see if the black soot follows the coil. This may rule out the coils or the wires. If not, then this coming week I'll have a chance to bring the bike to my friend's garage...he has a slick compression tester and he's a bona fide mechanic and Ducati aficionado.:D Hopefully there won't be a problem there.:p

One thing is for sure: I'm getting some new Magencors...just in case!
 

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Discussion Starter #11
An update (for those who are interested ;)).

Electrics all fine. Ran a voltage ramp up test and amperage test on the coils with a scope. Points to something mechanical.

Checked compression. Only 145 psi in the horizontal cylinder with 165 in the vertical. Pulling the valve covers confirmed it...the valve guides are worn! :mad:. Seems like Ducati had another metallurgy snafu which left a lot of us with sub par valve guides. Ducati's answer to the problem (when folks came in for warrantee repairs) was to replace the guides with the same defective units :mad::mad:. I have a dealer nearby that used to replace the guides with "race" guides. I'm going to call them tomorrow to see what they can do.

14K miles doesn't seem like a lot for this to happen! Oh well, I bought the bike knowing that this might be an issue one day.:rolleyes:
 

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An update (for those who are interested ;)).

Electrics all fine. Ran a voltage ramp up test and amperage test on the coils with a scope. Points to something mechanical.

Checked compression. Only 145 psi in the horizontal cylinder with 165 in the vertical. Pulling the valve covers confirmed it...the valve guides are worn! :mad:. Seems like Ducati had another metallurgy snafu which left a lot of us with sub par valve guides. Ducati's answer to the problem (when folks came in for warrantee repairs) was to replace the guides with the same defective units :mad::mad:. I have a dealer nearby that used to replace the guides with "race" guides. I'm going to call them tomorrow to see what they can do.

14K miles doesn't seem like a lot for this to happen! Oh well, I bought the bike knowing that this might be an issue one day.:rolleyes:

Odd that only one plug would foul. I didn't think valve guides were an issue for ST3's, in fact, this is the first I've heard of. :(
 

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Interesting that you could diagnose a bad guide by pulling the valve cover. Are you maybe seeing a torn or worn seal?
 

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Discussion Starter #14
Interesting that you could diagnose a bad guide by pulling the valve cover. Are you maybe seeing a torn or worn seal?
Slid the rocker over to take most of the pressure off. Able to rock the valve forward and back enough to see it move. The valve with the most play happened to be the intake on the side that has the plug fouling and dying. The other intake had some play and the exhaust minimal (may have been imagining things by then!) or none.
 

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Checked compression. Only 145 psi in the horizontal cylinder with 165 in the vertical. Pulling the valve covers confirmed it...the valve guides are worn! :mad:. Seems like Ducati had another metallurgy snafu which left a lot of us with sub par valve guides. Ducati's answer to the problem (when folks came in for warrantee repairs) was to replace the guides with the same defective units :mad::mad:. I have a dealer nearby that used to replace the guides with "race" guides. I'm going to call them tomorrow to see what they can do.

14K miles doesn't seem like a lot for this to happen! Oh well, I bought the bike knowing that this might be an issue one day.:rolleyes:

Wow, I new this has been a problem with some air cooled duel spark motors but didn't realize it Affected the 3 valve. Didn't notice any valve issues during my recent 6k service but I wasn't really looking for any. Guess I'll have to start checking from now on.


On the bright side, this will be a perfect opportunity for you to have some performance head work done. :D
 

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Howdo!

Had a couple of plugs die over the years. Running the superb Magnecor HT leads & Iridium plugs and bike starts a treat :D

Cheers Pablo
 

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Pablo, I've been thinking about Magnacor wires but how do I determine what set fits my 07 ST3? I see 7mm, 8mm and 8.5mm.
Do I need to replace my coils?
 

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Discussion Starter #18
According to Magnecor...no, you don't have to change the coils moving to a larger wire. I bought the 8.5 mm (because their red!). I haven't installed them yet. Look nice.
 

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I would install them and the new plugs, and give it a try. it might just perform ok with the little extra provided. Worth a chance before a tear down.
 

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Discussion Starter #20
By default...that's what's going to happen. I called a couple dealers. They're book solid for quite some time. I have a trip planned for the end of July into August...the bike will be okay for the trip.

Tonight I verified that the injector spray pattern for both cylinders looks good. The Ducatidiag software is GREAT! Now that the airbox is off, I have to do some cleaning.

New wires will go on this week. I'll get some iridium plugs too.
 
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