I feel like an idiot asking this question but like all in life, you learn from your mistakes (or stupidity, haha).

I'm trying to take the original Shimano 105 cranks off a Miyata 310 I picked up this weekend.

I took off the 13mm nuts and cant for the life of me slide the cranks off. I've tried oiling them up and nothing. I really didnt want to start hammering away at them and risk scoring them.

Am I supposed to be using a puller to get these off ?

Yes.

Yes.

+3, yes...and to add something *helpful*: since these are nutted you'll have the best luck using a Maxi style crank puller, instead of the standard style that works best on cranks with bolts. If you don't want to buy a crank tool, go to your LBS (one that has a Maxi puller) or ask around to borrow one, locally.

Or have the LBS remove them for you for a small fee.

So I got the left side off with a puller.

I cant get the gear side off. Ive tried, and tried, and i just cant get the puller centered to be able to get it off squared.

Any tips?

Uhhmmm.YES....puller needed, for sure....
That's why tapered, square ended bottom braket axles and square holed cranks replaced the old cottered crank systems...so they don't get loose and slip off so easily...or not come of with....uhmmm....banging a hammer on them, for instance.;^))

Chombi
84 Peugeot PSV

This is on an 86 Miyata.

It has the square ended BB axle. Cranks are square holed also.

Strange that the ones on my Univega slip right off/on but these are on TIGHT. Ive soaked it for 2 days in PB Blaster and cant get it to budge.

The drive side is a little tricker, since the top elevation of most drive side crankarms presents an angled edge, so that when the puller's in straight, it doesn't look straight.

Get a soft wire brush (or substitute a toothbrush) and clean the threads of the crank and crank puller, keep trying gently to get it threaded in there.

Geesh.

https://www.parktool.com/repair/readhowto.asp?id=103

Just a silly question but is there a washer still inside the pocket? Sometimes washers hide well, and sometimes someone slipped two thin washers in there so that when you remove one you think it's clear to proceed but really isn't.

We won't talk about why I ask this. 8-)

The "Case of the Hiding-Washer" is noted on Octalink bottom-brackets. Old square-tapers are more straight-forward. Make sure you have the correct puller. This, and a large wrench like a 12-inch adjustable, will work on both types:

https://www.parktool.com/products/det...=26&item=CWP-7

What kind of "puller" are you using?

The incorrect one.

$10 bucks at my LBS to remove the crank and gut the BB.

I'll bet you used a wheel puller, used for pulleys, etc.

I used to use a wooden wedge once in a while, and still do, once in a while.