It does sound fairly solid having given it a few taps. Does not seem to have moved any. I'm wondering whether it would anyway what with the gearbox and clutch assembled....
The other odd thing is that if I try to fit the oil seal the inner lip is always pushed out.
take the layshaft back out , heat the casing area and take the bearing back out first and check it is clean with no swarf or lumps stopping the bearing going in , apply a little heat and refit the bearing you can even smear a thin amount of grease around the bearing outer edge to help in go in , i always heat the casing around the bearing area to reduce the chance of any damage but some dont, then smear grease or oil around the bearing edges were the oil seal fits then tap it in gently and even all around if you dont have a socket big enough or a tool to fit the seal, then fit the retaining plates before you put the layshaft back in. remember to fit the o ring on the layshaft and again smear grease or oil around the o ring and it should either just push in or need a gentle tap .
ah looking at your last pic have you now got the bearing in , if so taking the layshaft out will help with getting the seal in.
The seal is the right size,the lip needs to go over the inner race.Try using the neck of a plastic bottle.Slice the bottle to make it the correct size to fit on the race,lubricate it and slide the seal over the neck and up on to the race,then tap into position.
Tried to do that but could not get a bottle cut to the right size, as the necessary diameter always seemed to at the join point of the bottle to the spout if you get me. Anyway I think the problem is because it does not have a chamfered edge so I have bit the bullet and replaced it for one that does.
cut a piece of plastic milk carton to assist in fitting the rear oil seal,not the bottle neck! just roll the carton plastic material place over the inner race and slide the oil seal into place using oil to help lubricate as you slide it home.simples!