Great thread and excellent information. :) I have a slight crunch when changing gear, I replaced with an Oberon, the fluid in the reservoir was dirty. Then a new chain, sprockets etc and it was OK after a proper bleed. Crunch came back, re-bled and it went again but is coming back grrr. I'm pretty sure I have a leak at my Master cylinder end. I can see a small amount oil under the dust cover but at first I thought it was spilt during the bleeding. For the sake of a £30 seal kit I might invest in the improved Magura cylinder for £138. I'll bleed again tonight to see if it helps again then I'll be sure my sights are set on a leaking original (25k mile) master cylinder.