This is where the fun started - just need to remove two counter sink 6 mm x 20 mm socket cap screws and pull the old seal out. One was fine, but the other had rounded off faces to it's hex socket, and no way would an allen key turn it.
I tried all the tricks I know:
- grind the end of the key to raise a burr
- peen the socket with a pin punch to close it up
- heat the screw cap with a red hot bar
etc etc and nothing worked - nothing for it but to drill it out
Now due to the nature of the beast this meant using a hand held drill - not nice in a situation where precision is called for. Now M6 tapping drill is 5 mm so theoretically if I can manage to drill 5 mm then I can re-tap which should dislodge the remains of the thread. Fortunately the screw was not high tensile - which is probably why it had been rounded in the first place, and also fortunately with socket cap screws you have a good chance of getting a pretty well centred drill to start with.
I selected a drill that just fitted inside the rounded hex, drilled all the way through, then worked up in 0.1 mm steps until I got to 5 mm at which point the top of the countersink came off releasing the oil seal.
A careful clean up, and an M6 tap produced an acceptable if not perfect thread.
OK pull the oil seal, but first clean up the shaft as there is a bit of surface rust. Now we can order parts.
The seal itself is actually a double seal with lips facing both ways, as not only does it seal against air pressure and oil, under some circumstances it has to seal against vacuum or 'suck'
20 mm shaft - the seal is £80
I was advised that the best way to buy it was as part of a 'Top Up' kit that had the seal, all the oil rings and gaskets, and various shims and bits. What with the Top Up kit and a filter / oil change kit I have no change out of £140
Bits on order - should arrive later in the week, meanwhile no air to any of the workshops
. . . it's amazing how often today I've reached for a blow off gun, forgetting there is no air !!
