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Discussion Starter #1
I have a 2004 ST3 that I am the third owner. Back in 2005, Ducati issued a service bulletin to replace the ECU and exhaust valve return springs. My ST3 does have the newer ECU, but I need to know if the springs have also been changed. I plan to perform a compression test and would like to know whether a good test result indicate that these springs are working properly. If this test would not confirm that the correct springs are installed, how else can I be able to tell that the correct springs are in there?
 

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It was my impression that the change in exhaust springs was to address breakage of the earlier units, not a weakness in the spring. Someone like Belter or DucVet can elaborate.
 

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The answer to your question is NO. A compression test tells you almost nothing beyond 'yes, there's a piston and valves in there'. Finding the source of any leakage requires a leakdown test and even that won't tell you if you have the revised springs. Then, there's what mlukason said.
 

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Exhaust valve springs were light on the early models and would not close the valve tight enough, this would cause a rougher running bike at low (under 4000 rpm). Changing to a stiffer spring did help this but there should be little to no harm running the lighter springs. Race motors commonly have lighter or even no springs and a broken exhaust spring gives similar results. If you suspect you have too light a spring or a broken spring start by looking for a broken one (should be one piece) .

If you find a one piece exhaust spring intact next make sure the bike is properly tuned and not just out of tune. If after a good and proper tune the issue is still there you could buy new exhaust springs and change them. While there you should check the valve guides as there is as good a better chance you have out of spec guides as bad springs.

What are you trying to fix?

To recap early exhaust springs were lighter and all years can break ( not common but I do keep one on the shelf).
If you do not have rough running at low rpm you are probably fine and check next tune.
If you do feel it is rougher than it should be get it tuned and check for broken springs or simply swap out to new springs on the exhaust to know. Check guides as well.
 

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If any service bulletins or campaigns were performed on your bike, a GOOD Ducati dealer should be able to look up this info. You just provide them with your VIN #. I was able to do this with my 1998 ST2 that I bought used in 2001. (And they had the database to do this back THEN!!)

The local dealer was able to verify that a handful of items were not done, and he was able to do these campaigns on my bike. He actually ordered the parts, and gave some of them to me, so that I could install myself! The shift lever (needed to be updated with a replacement), and the front sprocket retainer. The dealership did the alternator campaigns, as they needed to drain the coolant, oil, and remove the LH side cover.
 

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if you can get it on a 4 gas analyser somewhere and it has a shitload of hc and o2 in the sample then it probably hasn't been done. your ducati importer should be able to tell you if it was claimed, but that's not a guarantee it was actually done.

or pull a rocker cover and belt, slide the opening rocker across and push the valve down.
 

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Discussion Starter #7
It's great to have some many responses to my discussion. Thank you! The reason that I want to determine whether the springs were ever changed is that my ST3 runs poorly the lower in the rpm range I go. Even with the throttle completely closed I have a significant miss happening at the RPMs get below 4000. I have had the valves checked, gotten new belts installed, had the throttle bodies synchronized, had the trim set to 3% CO, changed plugs, changed the fuel filter, checked the coils and the plug wires. The problem persists. If the compression test doesn't point out anything out of spec, all that I can think of is either an injector or these springs. I have a 2005 Monster 620 and a 2004 999 and they both run great from idle to red line. If anyone has any other suggestions I would really appreciate it as I am getting very frustrated.
 

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Who ever adjusted the valves should have caught a broken spring so it would be worth asking if they checked the valve guides. I would try a leakdown test as well to find out if you have a bent or burnt valve. I have seen both that were still running but were poor at low rpm's . A valve can be slightly bent and leak so a leak down test will tell if you have good valve seal and tell you which one if you do.

If you still have no lucktry getting it on a dyno and no full power runs! have them run it where the problem exists and read air fuel on each cylinder. look to see if air fuel is good while the problem is there and if it is then it will probably not be ignition or fuel related.
 

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Discussion Starter #9
Who ever adjusted the valves should have caught a broken spring so it would be worth asking if they checked the valve guides. I would try a leakdown test as well to find out if you have a bent or burnt valve. I have seen both that were still running but were poor at low rpm's . A valve can be slightly bent and leak so a leak down test will tell if you have good valve seal and tell you which one if you do.

If you still have no lucktry getting it on a dyno and no full power runs! have them run it where the problem exists and read air fuel on each cylinder. look to see if air fuel is good while the problem is there and if it is then it will probably not be ignition or fuel related.
I believe that the springs are not broken, but the valve guides I'm not sure about. Tomorrow a leak down test will be performed and should shed some light on the situation. I will report on the results in a future update. Thanks Ducvet for your input!
 

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Discussion Starter #10
I finally was able have a leak down test done today. According to my mechanic(who I trust) everything looks good. We also did a compression test. According to the service manual, 150 psi is the minimum as "good". My ST3 has 145 psi on the vertical cylinder and 150 psi on the horizontal cylinder. One cylinder is below spec by 5 psi. Is this cause for concern?
 

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When comp testing we are more concerned with variation than outright figures. 5 psi variation is very minor and would indicate good condition.
Also when conducting a comp test always have throttle wide open otherwise you will restrict airflow and get a false low reading.
 

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Discussion Starter #12
When comp testing we are more concerned with variation than outright figures. 5 psi variation is very minor and would indicate good condition.
Also when conducting a comp test always have throttle wide open otherwise you will restrict airflow and get a false low reading.
Very encouraging! We didn't have the throttle open so hopefully doing that would have improved the measurements. I will have the test redone once we get the fuel injectors back after they have been cleaned and flow tested. Thank you, Turbomart!
 
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