Katana 750 shock adjustment

[davidsvoboda]

Hi, I just replaced my old shock on my gs for Katana 750 (2005) shock with reservoir.
http://www.ebay.co.uk/itm/111310955984?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2648

It is pretty cool but very stiff. Also it kicks really bad on the bumps.
I can adjust it down at the shock but damping adjustment on the reservoir I cannot seem to turn with a flat screwdriver. Does anyone have any experience with the shock? Am I adjusting it wrong?

Many thanks!