Thank you very much for your replyThe gear on the mainshaft is actually a nut. There are two flats for an open end spanner between the gear and the bearing - visible on your photo. The spanner size is 29mm if I remember correctly, but needs to be ground down until it's about 3mm thick. This nut is also staked on the mainshaft at its outer side and this needs to be undone first.
Thank for your helpThe gear on the mainshaft is actually a nut. There are two flats for an open end spanner between the gear and the bearing - visible on your photo. The spanner size is 29mm if I remember correctly, but needs to be ground down until it's about 3mm thick. This nut is also staked on the mainshaft at its outer side and this needs to be undone first.