Help Needed steering bearings replacement

[Theo]

At 89 hours of motocross and despite no obvious reasons for which this should have happened (slight preload as per the 12 Nm specification, no rust, etc.), I've noticed that the outer race of my lower steering stem bearing has some shallow wear. The worn spots can't be felt by rubbing my fingertip but they can be felt by rubbing a plastic tool over them: the tool gets gently caught by them.
The handlebars turn smoothly without any play and I wouldn't know about those damages if I hadn't disassembled the bearings to re-grease them.

Surely the condition of that surface is not going to improve if I don't replace the bearing, so I'll have to do it. I'd like to replace at least the outer race on my own and I'd like to do it minimizing the risks of damages to the bike. I've never done this and I've read that it's usually a pain in the ass without the right tools.

• In order to remove the worn race, I was thinking of getting the Motion Pro Steering Head Race Puller, part no. 08-0737, since it seems like the best tool and it's not crazy expensive.

• Driving the new race into the frame seems more troublesome because I'd like to use a proper tool but the outer diameter of the bearings is 50.3 mm and I haven't found a race driver that is compatible with that dimension. Is the race driver supposed to contact the face of the bearing like in figure A or is its tapered surface supposed to push like in figure B? I guess figure A and that the tapered part of the driver exists only for centering reasons. In this case, a Ø50 mm tool may work because the tapered part wouldn't touch anything and hopefully the lip of the face would still be enough.


• For the part of the bearing installed on the stem, my plan is to simply bring it to a shop and have them replace it.

Any other suggetions or thoughts? I'd like to avoid tricks like utilizing the old race after having slitted it because I'd like to keep the components as square as possible.

 

[Kurlon]

You want your driver working like Figure A, pushing on the top of the race, not the bearing surface. The old school trick is use the old race flipped upside down as the driver for the new race. I've never slit them to shrink them up. I've got a Tusk steering stem press kit that was cheap to source and makes putting races in easy. I use a Park tool race driver to remove them, again, ez-mode, half the cost of the Motion Pro puller.

 

[Theo]

You want your driver working like Figure A, pushing on the top of the race, not the bearing surface.

Thank you, as I suspected; I just wasn't sure.

The old school trick is use the old race flipped upside down as the driver for the new race. I've never slit them to shrink them up.

The problem that I see is that in the Varg the outer race doesn't seem to be flush with the edge of its bore, it looks like it goes a little below it. I think that the old race upside down would get stuck if it's the same outer diameter, or maybe not if the chamfers are enough to cover that gap. I could still grind it to be sure, it's hardened steel so it would take some minutes, but probably once like 0.1 mm has been removed it would just fall in.
I'm afraid I could drive it crooked, though, while a race driver gives me the idea that I can keep a better alignment.
Or I could put some kind of steel plate/wooden block behind the old race and hit it in the center...

 

[Kurlon]

It 'may' stick in, but also remember that the new race has gone in ahead of it, so that bore has the new race working against it, and you're not sinking the old race in that far. I've yet to have one noticeably stick, and if it does you can just tap it back out with a drift through the neck, 'cause again, old race, who cares what you do to it.

I wouldn't hammer the new races in, even with a nice drift. If you don't get a tool like the Tusk press kit, some big threaded rod, big nuts, washers and you can make your own installer press using the old races as drivers.

 

[Theo]

It 'may' stick in, but also remember that the new race has gone in ahead of it, so that bore has the new race working against it, and you're not sinking the old race in that far. I've yet to have one noticeably stick, and if it does you can just tap it back out with a drift through the neck, 'cause again, old race, who cares what you do to it.

I wouldn't hammer the new races in, even with a nice drift. If you don't get a tool like the Tusk press kit, some big threaded rod, big nuts, washers and you can make your own installer press using the old races as drivers.

Pressing the race surely sounds like the proper way. However, the Motion Pro part no° 08-0669 doesn't have a compatible driver and other alternatives are expensive and rare, except maybe the Tusk.
I think the Tusk press you are talking about is this. I've read the questions and the reviews on the RMATVMC site:
• The kit includes three Ø50 mm drifts, that I assume would be compatible with our Ø50.3 mm bearings.
• The kit also includes a driving handle to be used with a mallet in case one decides to do so.
• Unfortunately, more than a person reported a thread failure or a hard time keeping the tool aligned. They ended up using the mallet. Others are satisfied. I doubt I can make a DIY press that stays aligned, then.
• The handles are pretty wide and someone didn't manage to turn them because they hit parts of the bike like the frame.
Has anyone used this Tusk tool successfully on the Varg?