Wrong BB in most Yo!s
Note: This is for period correct Shimano cranks aka the first gen of "low profile" Shimano crank offerings that still use a square taper... Basically the latest incarnation for square taper dimensions and NOT after market cranks; for those you are on your own as there was no apparent standardization.
For the first gen single unit Shimano cartridge BBs, if the shell is 68 then the recommended spindle length is 107 and if the shell is 73 then 113 - this from Shimano tech literature. This is a recommended place to start for ANY bike from the 90s era that uses this threaded BB and square taper setup.
I see a TON of people with a 68x113 (It is actually quite difficult to find a 68x113 as it is not technically a standard size) in their Yo Eddy's, in fact my eBay bike came this way (With '95 XT cranks) and the chain line was HORRIBLE! I swapped out the M900 UN91 (boohoo me) for a UN72 that is 68x107 and it is wayyyyyy better - correct in fact. For some reason 113 seems to be the standard for earlyish 90's Yo!s and I'm really not sure why this is, anyone know? Was it to correct after market cranks or something?
So if any of you out there have a yo with shimano cranks and a 68x113 then most likely your chain line sucks and a 68x107 would very likely help you out a lot. A telltale sign is that the end of the crank arms are way away from the chainstays when in fact there should only be about 5-7mm of clearance as is the case with a 107mm spindle length.
PS - Has anyone else realized that a hub "axle" is actually a spindle and a BB "spindle" is actually an axle? Just wondering.