[dewcatty]

My bike is an ST3 2004 model .
I just decided to do the service on my bike so that means cam belts and valve clearances as well as the oil and coolant change.
When I pulled the horizontal cylinder exhaust valve cover I found a piece of one of the valve springs sitting down there .
So now I need to swap the spring there. I looked at Brad's explanation of how to change all the springs which involves total removal of cam , rockers, valves and shims .
I'm wondering if all that really needs to come out? Brad was working on an 851.
Would it not be possible to just extract the shaft out enough to free that one spring, which is on the belt side, while leaving everything else in place? I still haven't found out if it's a pair of springs or if it's all one double spring though.
The other issue is why did it break and whether I really need to replace all of them?
Your thoughts would be much appreciated.
I posted this on the Sport Touring forum as well but thought it might get more attention over here. Cheers.

 

[highflyer]

No need to remove the cam(s).
Just the opening rocker(s) as needed.
https://www.ducati.ms/threads/broken-valve-spring-2005-st3.25962/
Shot peening the springs improves their fatigue resistance up to 30%.

 

[Turbomart]

Pretty sure 851 is a 4 valve motor so will be different.

 

[dewcatty]

I now have the new spring and have looked at everything I can find on the subject and also stared at the actual engine for a fair while . Tomorrow I'll tackle it. First I'll remove the belt, then the cover on the ends of the rocker shafts. Remove the opening rocker clip, withdraw the opening rocker shaft and withdraw the opening rocker.
With engine at TDC for that cylinder before I started, I then need to remove the closing shim and valve retaining thingos. Not sure if I'll make up a spring depressing tool for that yet.
At that stage I intend to remove the closing rocker shaft and I'm hoping that the closing spring is at rest there or at least not overly prestressed before assembly.
It looks as if the closing rocker can be withdrawn at that stage after which the spring can be replaced and reverse procedure.. I was told that the end of the valve stem might get in the way and may need to be withdrawn by backing off the engine a tad but I'm hoping this won't be necessary.
I'll run a camcorder on the job and may upload it if it turns out OK.

 

[mlukason]

One item of note...my ‘06 ST3 has “split” pulleys that allow for adjustment of cam timing. I don’t know if the ‘04 had them. Just make sure you don’t separate them (if you have them) or you’ll be adding a step or two to your procedure!


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[duc96cr]

No need to remove the cam(s).
Just the opening rocker(s) as needed.
https://www.ducati.ms/threads/broken-valve-spring-2005-st3.25962/
Shot peening the springs improves their fatigue resistance up to 30%.

I’d be surprised if they weren’t shot preened already. I worked at one of the largest international spring manufacturers and we shot peened 100% of the springs we made for at least the last 30 years. It’s highly unlikely the replacement wouldn’t be shot peened, it’s pretty much industry standard. Look for a unsmooth, sort of textured surface. If you were to get a spring shot peen that wasn’t already you have to properly stress relieve it in an oven afterwards.

 

[belter]

I now have the new spring and have looked at everything I can find on the subject and also stared at the actual engine for a fair while . Tomorrow I'll tackle it. First I'll remove the belt, then the cover on the ends of the rocker shafts. Remove the opening rocker clip, withdraw the opening rocker shaft and withdraw the opening rocker.
With engine at TDC for that cylinder before I started, I then need to remove the closing shim and valve retaining thingos. Not sure if I'll make up a spring depressing tool for that yet.
At that stage I intend to remove the closing rocker shaft and I'm hoping that the closing spring is at rest there or at least not overly prestressed before assembly.
It looks as if the closing rocker can be withdrawn at that stage after which the spring can be replaced and reverse procedure.. I was told that the end of the valve stem might get in the way and may need to be withdrawn by backing off the engine a tad but I'm hoping this won't be necessary.
I'll run a camcorder on the job and may upload it if it turns out OK.

if you pull the inlet opening rockers it'll allow you to spin the cam around without interference, might be worthwhile. otherwise where you can place the cam will be constrained somewhat. keep an eye on all the steel shims.

when you pull the exhaust closing rocker pin the rocker might try to fly out. there's a lot of force on those springs, esp the later style / service replacement, it's not just a put it in the head and slide the pin back in deal. you might need to make up a holding tool of some sort to get it all back in. be wary of the valve stem seal.

 

[dewcatty]

Belter, thanks very much for that info. That's exactly what I was concerned about. So with the cam out of the way I wonder if the closing rocker could be released away from the spring pressure? Guess I'll find out.

 

[belter]

i don't know that you'll need to remove the cam. but the spring needs to be compressed to fit, you can't get away from that.

 

[dewcatty]

I just got the new spring in with a minimum of fuss.
Removed the cover on the end of the camshaft, horizontal cylinder.
Removed the opening rocker and shaft with shim and clip and steel washers.
Pulled out the closing rocker shaft. The thread in the end is the same as my small fairing bolts and the shafts require no effort to withdraw.
Pushed the closing rocker down to remove the retaining clips and the closing shim.
Withdrew the broken spring with the closing rocker in the middle.
Placed the new spring in place with the closing rocker sitting in the middle. No fiddling required.
Pushed the shaft across into the right side of the spring[facing the rockers] and the closing rocker.
Used a screwdriver under the left [timing belt side]side of the spring to align it with the shaft.
Used a very light leather hammer to tap the end of the shaft which then engaged into the left side of the spring and straight into the housing with no problems.
Rotated the cam to allow the closing rocker enough room to refit the retaining clips.
Refitted the opening rocker.
Job's right. Took weeks of angst and half an hour in the doing. Not much more time than writing this.
Thanks for all the help and dire warnings. It's been an interesting journey.