What you have there is a separation between the steel sleeve and the aluminum case.
Now I’m seeing what you’re saying but I can’t imagine how that would happen unless that bearing pocket is severely warped or the hole it’s in was totally out of round.
Did something move while the pocket for the liner was being machined but they put the liner in anyway. If that’s the case then it’s been that way since day one. Or, wow does the engine hammer the aluminum that bad?
I would say it has to have the pocket machined out and on center for a slightly bigger liner that will have to be custom made.
Anyway Pete, if you heat the case your other little bearings might want to float off their seats and if you’re thinking on it, removing the steel liner in the main bearing pocket will be very hard with just heat.
You need one of two people Muller Machine or me and (lol) I’m busy.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience