Shims are only to keep axial loads to a minimum. +.15 --- +.25

Nothing to do with bearing loads.

Nothing to do with cyl. axis.


cliff

Yamfan wrote: On the TY175 the bearing races are very slightly above the crankcase faces, and even with the crank fully home in left and right bearings, there is around .5mm clearance on both sides.

Outer bearing race is stationary and flush with inner race.  Crank can and will rub without shims in many instances.

Later models without shims had a small "step" machined into the crank stubs that takes the place of the shim. 

Bearing loading, meaning hammering back and forth axially as the crank accels and decels through the revolution.

Must minimize this axial "load" of hammering.

cliff

Talking main bearing problems.
I did a Harley 1100 sporty at work under warranty in i think 1986 & the left main bearing [two bearings] were taper rollers with a spacer between.
Man that was fun i'd rather not have lol--wasn't easy to get perfect & had to be perfect.
The bearings had roasted themselves from having too much preload & just overheated.
Maybe it was a known likely fault--[bad day at the factory]--& they covered the cost & supplied the parts.
Well i doubt they covered all the labor time as took a while heading into unknown territory.
New Spacer had to be shortened to get exactly the right preload or neutral load yet no play.
Can't remember how i measured the end float then shortened the spacer [lathe i guess] But was rather stressful although ended up good luckily.
One of the local fast guys on a YZ360A tried taper roller mains in his bike. Not sure if it was successful or if he used tapers both sides but guess he just shimmed it to neutral play. I saw it dismantled once but didn't get a good long look or get to ask questions.

I load pics on google photos at the moment then link it. Seems to work for me. First hit upload & get your photo on there--then there's a triangle thingy [like a V on its side] up top on the right which you hit to share then another window opens which has a create link at the bottom which then brings up something which says create link to share. Then hit the create link 'blue bar' & copy the link it will create then paste it Here on your post. Sounds complicated & was for me with geriatric computer skills until i mastered it. Now its easy.
There's probably easier options others use though.
photos.google.com/
Just trying the link above it seems to go straight to My Google Photos Page but probably only because i'm signed in, not sure. Let's know if all my pics come up please.