demographig,
You need a bearing who can handle what rpm you use mostly.
C or C1 is stock and can handle burst up to stock toprev, but generally
not more than and 5000 rpm.
The heat and poor lubrication are a "killer" and you can make the feeding gas/oil holes flow better
and bearings life easier.
Hughes,
A friend of mine true and balance my cranks.
I will changes the balancefactor from now 5000 rpm (MX) which is stock to a another rpm.

//doordie