That bearing failed on my Jota a couple of years back. I had to split the crankcase to fix it. As Piet said.
I've heard that some people do it by turning the engine upside down and lifting the bottom half off like a lid. But I did it with the engine the right way up, putting lifting strops around the ends of the crankshaft to lift it and the whole upper assembly away from the bottom half leaving the barrels, head, cam chain, etc. undisturbed. Doing it that way leaves the clutch and gearbox internals sitting in the lower case. Reassembling the gearbox is a whole lot easier if you do it the right way up.