R-L,
If there has been a noticeable drop in stopping performance and you are still generating the required clamp force at the caliper (check very carefully that you can ease the pads away from the disc friction face a couple of mm and that the pistons move back into the caliper housing - apply the brake - does it clamp up again very easily?) and your pads are still within their servicable limits and your discs still look pretty much like they always have, then you have probably contaminated your pads. I am assuming here that you have not well and truly 'cooked' your brakes.
The original pads are sintered metal construction and as such, they are much less tolerant to contamination by oil, wax etc. than conventional organic pads. Maybe it was a bit of over zealous lubing/spraying of the surrounding parts?
A good check would be to replace the pads and see what happens - I have found the original spec pads to be generally OK. I would use another OEM set before going for something a bit more 'exotic' (read, higher, more consistent friction value, but less pad and disc life). Caution here - when your discs warp (and they surely will, because they all do), then, if you want to get the discs replaced under warranty, you had better make sure that the Duc dealer does not spot that you have had got any pads fitted that are not OEM spec.
Finally, do not lube the pistons - they do not need anything more than the lubrication provided by the brake fluid.
Need any more help - drop me a mail
Cheers, Chris.
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