Sorry I got so far behind here, I have a S'T' carb thingy that's driving me nuts.

My pictures are rather at random, and don't show everything perfectly at all times. Firstly,
crankshafts are trued in the real World by bumping them with a BFBH....that's brass. Heavy
and soft. The hammer we had at the M/C shop 4" wide on the face and weighed about 8 pounds.
It was brass on both ends. After the crank haves are pressed together (with news parts in the middle)
using special alignment jigs, the assembled crank is checked in a truing stand.

Every now and then you get one that's perfect, but 95% of the time you have to true-up the crank.
You whack it with the BFBH. The whole thing about being an m/c mechanic (and we used to laugh
about this) is "knowing where to hit it, and how hard". You hold one flywheel in one hand, and whack
the other one. The flywheels will (believe it or not) turn ever so slightly on the crank pins if you strike
it correctly. You can move it about a thousandth of an inch or more with the correct blow.

Once you get it trued up to about .001 your in business. Sometimes you can get them perfect, but
sometimes the tolerance on the parts themselves do not allow perfection, because they are off a little.

Now if you have a twin, you assemble and true both cranks separately....then "block them up" with metal
wedges so they don't move....and press both cranks together with new bearings and seals in between.
Then back to the truing stand to check and true the assembly. The multi cylinder assemblies are trued
in a hydraulic press. These procedures are done by the old timers at the shop....trust me on that. I've
done hundreds and hundred of cranks during my last 15 years at the shop.

These little aero-model cranks are childs play really....I could true them in my sleep.

1. a single cylinder
2. a triple
3. a mechanic spot welding the pins on a racing crank after he has it perfect.

FBD.