My crank shaft is one piece type.
I think impact screw driver can be very useful for some screws in there.
And while in there, I changed all 4 bearings with Japan made ones.
I splitted the crank case carefully, then I could reuse the crack case gasket with no leaking problem.
The flywheels have a metal cover each side.
I used angle grinder to shave some weight off inside both of the flywheels.
Then when I put the covers back on, the shaved cavities were all covered, thus no change in crank case pressure ratio.
I found trouble when unscrewing the wide flat head screw on the small pinion gear, even the impact driver couldn't work, it still stripped the flat head screw, so I machined a flat head screw driver out of a chisel that can take the whole width of that stubborn flat head screw. Using this, it unscrewed easily by also using other tool to help turn the chisel.