Steering Stem Bearing Replacement
Here is steering stem bearing replacement on enduro motorcycle Yamaha WR450F 2012. The similar procedure for most offload/mx/dirt bikes. We had problem with inner race of bottom bearing and solved it loosing the inner race by Dremel. Using chisel, like it's written in manual looks impossible. Also we don't think, that you can cut the inner bearing race and split it with a chisel. Very difficult or impossible to cut the inner bearing race enougth, as you can touch the clamp and can not make 90 degreee cut, only curve.
The main reason of stuck races is water, which leads to rust. We recommend to thoroughly pack seals and bearing with grease to prevent water from entering. Also, if you drown the bike in the water - disassemble steering stem and maintenance bearings like all bearings of the bike.