Bandit 1200 K6 Wheel Bearing Maintenance and the Wiggly Adventure

I replaced the wheel bearings, but
 

 
I forgot to order the oil seals…
What a dummy I am, seriously ★
So I’m moving on with a temporary fix for now!!!
 

 
K2 Factory’s whatchamacallit kit
 

 
I was curious so I pulled it out!! Is that an O-ring?
Is that okay? Since it’s for the clutch, is that okay? I’ve never seen one before
 

 
40Φ
 

 
OEM 38Φ
2Φ up ★ It’s a matter of the ratio between the master side and the piston side.
I thought 2Φ sounded like a lot! But I didn’t really understand it… sorry for being honest.
Did it get a little lighter somehow?
 

 
I have to remove this area (・。・) or it won’t work, and it’s a mess…
 

 
Front sprocket…