Ok so i have a ult on off that im tryin to get running. So far it wants to run away. I used dial calipers to measure the shims. I found that all 3the shims that were in it are level 10 shims so i know thats a problem but i noticed the little black oring isnt staying in place its sliding to the botom of the pin. How would one replace that oring? Or what should i do. I know i need to reshim it but wondering what to do about the black oring?

All info is greatly appreciated