selector fork shaft. Bush positioning

Well I am stuck already on my engine rebuild on the very first reassembly item .

I knew that I would have to resolve this issue before I could start which has been putting me off starting. To tell you the truth its the reason the previous owner gave up and sold the bike to me.

Its the crankcase bush and needle bearing race for the selector fork shaft that is the problem.
For some reason the PO tried to remove the bush with a puller because the needle race had broken up. he thought it needed pulling until I showed him it is just a straightforward press in /out job. He was gutted.

My question is this .

Should the new bearing be pressed in so that the front lip of the bearing is flush with the inside face of the case ?

This one is sitting proud by 1.2mm which could be the result of the po trying to pull it out before I got the bike.

Could anyone with an open case check for me please .

I could just press the new one in to the same position but it may end up with too much or too little play for the selector shaft.

When I installed mine I just made it flush with the internal side of the case.

thanks hotdog. I figure its not too critical andwas probably meant to go flush.
How did you press your bearing in ? or did you get an engineering shop to do it ? Wondering if its possible to drift it in with a hammer

You could drift it in, just take it steady & use a nice big drift.
I used my 12t shop press to do mine, from memory it was not too tight, I did coat the OD of the bearing with a tiny bit of 3bond before assy.

Peanut, a little heat on the case around it will also help make it easier to tap into place.

thanks for that tip Brian. i did consider bashing ......ahem drifting, the bearing out and a new one in with a hammer but the possibility of damaging the casing was just too bad a scenario to contemplate so I got it pressed in at a precision engineering workshop today.

ok just to close this thread for possible future reference I'll post the solution that I found today.

Had I been the person to strip the engine I probably would have appreciated how the fork selector shaft functions and is held in place but I bought the engine stripped in cardboard boxes. it was only after studying all the components that I have discovered how they all relate and function.

The precise seating position of the needle roller bearing for the gear selector drum in the engine casing is not actually as critical as I first thought.

The selector drum is held in position by a crescent shaped anchor plate which functions as a double sided thrust race. Allowing the drum to rotate but preventing the selector drum from moving laterally in the case.

This prevents the end spigot of the drum from grinding away the face of the needle roller cage .

The existing bearing was set approx 1.2mm above the inner face of the casing so we pressed the new bearing in to the same position. If the bearing sat any further out into the casing it would probably grind on the end of the selector drum but we reasoned that if the bearing was pressed flush with the inner face of the casing it would be fine and at least 85% of the needle roller bearing would be in contact with the end of the selector drum spigot.

The steel case of the bearing is very thin and would be easy to distort if it wasn't pressed or drifted in square and evenly. We decided to press the bearing in from the inside of the engine casing (using the drum itself as a drift ) as it was easier to provide adequate support to the engine casing within the press.