It's a separate gearbox so not exposed to the same combustion contaminants that the engine is. At least the gearbox is cleaner on the inside than the outside.
So, rebuilt the selector mechanism with the new springs and cleaned up the sealing face. Cleaned up the matching faces on the gearbox. and used a light smear of silicon gasket as a sealant. and basically reversed the process. Measured out the excess oil and lobbed it in. and buttoned it up. Elevated the rear wheel and run up and down the gear box nudging the rear wheel around by hand. Then flicked on the ignition and neutral would be correct, so https://www.facebook.com/video.php?v=746912482027828 So, no leaks.
Well the JnS breakfast was great! Good to catch up with Mr & Mrs Rock Steady, JimmyTanko and Grizzer. The gear box was better than new. Nice and slick, but run in too. Unfortunately I messed up the TransLogic clocks calibration trying to zero the trip when I filled up. :bang: I must get my head round them and ride it more so I remember.