The 760 270 I bought was real dirty on the inside. I stripped it all down and used brake cleaner on all the parts. The tube that has the locktite came loose after I heated the tube with my wifes hairdryer, too cool !! The o' ring looked fine and I just oiled it and left it in place. The only tricky part was getting the dust cover back in place.
If you have a 760 don't be afraid to take it all down to clean it , I'll do this one again in 20 years if I'm still kicking ! FBC