loose exhaust clamp

[jerry]

The left hand 12mm bolt clamp on my S4 never gets tight i have widened the slots on the pipe so they should clamp up tighter and also taken a 3mm chunk out of the clamp but the exhaust is still loose ,so the can wobbles. any ideas.....shim gaskets ??

the clamps on my 2 other dukes get tight and so does the right hand one on the S4

[big pete]

Hi Jerry, probably a stupid question but is the bolt getting thread bound and if not has the clamp stretched. May be time to buy a new one. Just a tuppence worth , sorry if youve looked at that.

[jerry]

Bolt is new , clamp is same size as right hand one , I have shimmed it which has improved tightness .

[big pete]

Good man Jerry, sounds like Ducati's manufacturing tolerances might be out a bit!

[utopia]

I'm not familiar with an S4, but are we talking about a ring clamp over the junction between two sections of plain pipe (as on my 750) ? Sorry if this is still a stupid comment but if, when you tighten it all up as far as it can go, there is still a gap in both the slots in the pipe and between the ends of the clamp, then it does seem like the problem might be the bolt getting thread bound somehow. Does the bolt have a plain, unthreaded section below the head ? If so (and sorry again if this is obvious) will it clamp up tight with a couple of washers under the bolt head (or preferably another bolt which is threaded along its entire length? Have you tried swapping bolts with a clamp which is known to work, or even swapping complete clamps over? Alternatively if it is threaded all the way along, does a 8mm nut run easily down the full length of the bolt?

[jerry]

It tightens up fully all the way

[utopia]

How do you mean...all the way?
If it tightens up, on the bike, until there's no gap left in the clamp, then it can't be putting much, if any clamping pressure on the pipes.
You say you've already widened that gap by 3mm, so all I can think of is that the weld holding the threaded section on to the clamp is failing such that tightening the clamp is merely trying to pull the threaded part off the clamp.
I'd still try a couple of washers under the bolt head, but that may just pull the threaded bit off even further. At least you'd be able to see it then though.
As has been said, looks like a new clamp, or a weld-up of the old one if you're stuck for a supplier, or maybe a jubilee clip....?