I'm firmly convinced that most cases of so-called "warped" discs are incorrectly diagnosed.
Far more common (in my opinion) is the uneven surface conditioning that Gazza describes.
In the past, the discs on my 750 suffered from mild pulsing for quite some time but the same discs have been performing perfectly for many years now.
Here's a thread on the subject.
http://www.ukmonster.co.uk/monster/s...t=warped+discs
ps. I never did get round to fitting the full-floating bobbins mentioned in the thread .. the discs remain as standard as the day they left the factory.