Hi Deejay and thanks for the response. I did see your video on how to remove engine and dismantle the clutch, that's what inspired me to have a go myself. Although unlike you I wouldn't dare bring a lawnmower inside the house to dismantle, my wife would lynch me up. I do have good sets of spanners sockets etc and good low workbenches as my passionate hobby is woodworking.
I'll have another go at getting the chain cover off. Prior to the last major service I would frequently take the cover off to check things and put a bit of oil in. Unfortunately the mechanic decided to overtighten the 2 holding screws and I've had trouble undoing them. I'll try to get a screwdriver to fit the slot better and have a go tonight.
I have got an old working rotary mower so being without the SB for a period while fixing it won't be a problem.
Regards
Garry
