Swingarm bearing seals findings and upgrade (hopefully)

I currently have the swingarm off the bike for doing maintenance on all those bearings and actually to change out the shock for the Hyperpro one that should arrive sometime this month.

It's the first time I have done this to that extent. Now, the swingarm bearings were still in good shape with sufficient grease inside, as opposed to the linkage ones. However, I noticed that there must have been some minor ingress of water and dirt from the outward side of the bike. One can tell by some traces of rust in the grease and how the bushings look like.


The bearing housing tubes on the swingarm are sealed off by an oil seal on the inner sides, where they touch the gearbox casing. The outward sides have no such seal, but caps with some seals appearantly vulcanized into them, which seal against the outside of the bearing housings. There is no seal against the inside of the housing and the bushing - hence the ingress of shxx there.


This is what the outward side looks like in real life.


The inner side comes with a seal:



I had available a full set of bearings and two new spare oil seals ( no. 2 on the manual drawing). I did not touch the bearings, just cleaned them out as good as possible and re-greased them properly. There was nothing wrong with these. Normally I would have changed at least those oil seals. However, since there was no apparent damage to these, I decided to go another way.

I installed my two spare oil seals on the outward side of the bearing housing, so now the bearings are fully sealed off.

There is plenty of space to do so (15 mm installation depth of the outer bearing). Also, there is no pressure lock or something when putting them in, because of an orifice in each bearing housing into the swingarm inside, where each leg itself has a drain hole on the rear end bottom.

With additional seal and bushing already installed, but not the cap:


I wonder why Yamaha saved costs on such a small part. I am grateful for any idea why they did that or what could go wrong with my little upgrade. I just fail to see any reason why not to have the same seals on the outer side of the bearing housing too.