Sacrilege?

OK, I am not a SunTour expert. But I am holding what appears to be an Alpha-5000 (photo from Velobase below) in what looks to be pretty good shape. I want to breakout down, and the upper pulley is not playing nice. There is a protrusion on the take-up spring housing to engage a stop -- that's fine. But the placement of the upper pulley precludes the pulley mounting bolt having its head on the DS or it would get in the way. Thus the upper bolt, and only the upper bolt, has its head on the NDS. And, presumably to ensure that head does not hit the spokes(?), this bolt has a very shallow head. And it is seized. Despite PB Blaster. Due to most sockets having a little recess so the face of the socket does not lie flat against a bolt's mounting surface, the sockets do not engage the flats (oh, 9mm by the way) adequately to break it loose. I have nice open end wrenches, but I am starting to round off the wrench flats. Not happy; I cannot re-grease or replace the pulley. I've considered Dremelling through the center of the pulley and seeing if I could grip the remains of the bolt in Vice-Grips - -but then I'd have fun trying to source a replacement bolt. I am also considering taking a 9mm 6-point socket to a bench grinder to make its engagement surface 100% flat and get another fraction of a millimeter contacting the bolt head.

One presumes that the location of the pulley is geometrically "perfect" but I am kinda seeing a design compromise that makes service so close to impossible.

Seizing sucks, but I don't think the Maeda engineers factored that into the pulley bolt design.

And yes, some Suntour pulley bolts of that era have remarkably "low profile" hex heads. But I've had worse problems with stuck pulley bolts that need a 3mm Allen to remove - those are all too easy to round out applying break-loose torque, and are then much harder to deal with once the intended tool no longer turns them.

Long ago on my 8-9-10 Y wrench I ground down the socket faces to improve engagement on bolts of this type, so that could help.

Sacrifice a cheap socket and cut the end off so it engages. Or dremel a slot and use a screwdriver

Grind off the face of the socket. You'll be surprised how quickly a benchtop belt or disc sander will do it.

Use any flat stamped-steel spanner, they'll have six-sided holes and will act on the whole of the faces.

I've got lots of sockets and closed-end wrenches that I've "squared" over the years, usually on the belt sander.
Similar situation with the lo-profile chainring bolt heads on some steel cottered cranksets, and with centerpull brake caliper pivot bolts.

Other tools (sockets and open/closed-end wrenches) also having grinding done on their exterior surfaces, to minimize some particular dimension, for clearance.

Nothing too egregious here, since the bolt has a low-profile head that is not all that uncommon.
And since (using a hex-head facing the spokes) would have been no problem in that era of wasted clearance space typically found to either side of freewheels (I'm more bothered by those Suntour derailers where the outer cage plate encompasses the guide pulley, necessitating the special remover tool while precluding the option of using narrower pulleys).

With the advent of 8s cassette widths, things got crowded back there and any/all bolt heads finally needed to be flush along that inner cage surface.

This thread reminded me how much I marvel at the space-efficiency realized with the advent of 10-speed gearing, when these new (10s) cassettes were actually so well dimensioned and offset that they can fit onto a completely standard 7s HG (not HG-C) freehub having 126mm spacing and normal wheel dish.

On a remotely-related topic:
I was going to do a post about this yesterday because I found a current source for long-threaded (6+mm) alloy cassette lockrings on TEMU, shipped out of Los Angeles in just a couple of days (not weeks like from AliExpress).
I stocked up, since these "11t" lockrings nest into the recess in the 10s cassette's 12t cog, allowing a good few thread turns of engagement into a 7s HG freehub.
Previously, I had used certain of SRAM's ALLOY lockrings, but which have become very hard to find in such (1/4") threaded length.
So I had used all of mine mine up fixing bikes having damaged freehub bodies!

Search word on TEMU for this part is "HASSNS cartridge freewheel locking cover 7075" (it was very difficult to find using search).

I don’t know if you tried. I would remove the lower pulley and rotate the cage plate counter clockwise. That usually works on those.

Easy, I guess to simply conclude that, for instance, Campagnolo designed their products with a. long lifespan, and thus rebuilding, in mind. And that could possibly be quite wrong. But I've never had this trouble before.

I've had my trusty 8-9-10 since about 1976, a trusted old friend -- I think I'll grind something else first.

I'll report back on whether modifying a socket works. I cannot imagine a screwdriver slot oil. enable enough grip when the 9mm wrench wouldn't.

Oh, yeah, tried that early on. No success.

Second thing to try, slobber with penetrant and put a heat gun to it. Use a wrench and pull the cage plate. You can get very hot to the touch without damaging the pulley.

or just lube it up put it back together call it a day.

My vote is for first trying the above idea of rotating the inner plate, to get the bolt turning. If that doesn't work, all the heat and penetrant won't get a socket with a taper to properly grab that shallow head. This is a legitimate use case for filing the taper off the face of the right-sized socket.

Success! (Special tech hint: once grinding the socket, allow to cool before handling ) So, now I have one odd 9mm socket, perhaps I should put a little SunTour sticker on it.

With replacement pulleys arriving as soon as today, I really wanted to break this loose. Actually, once the socket could no longer "cam out", it was not a stupefying amount of torque needed.

I still think it could have been designed differently; either a slight change in where the pulley is attached to the cage, or some change in the rotation-stop on the take-up spring's housing.

No worries. Shimano took care of that.

Next time I have the opportunity to examine a Shimano, I'll have to check that out. None here, however.

Many years ago I made a small set of metric ground down sockets - 10, 9, 8, 7, 6mm, 1/4” drive. That set stays with a small pile of tools that are handy for bicycle work. You will encounter thin headed fasteners again and it’s handy to not worry about damaging hard-to-replace bits. And the lack of that end taper* does not slow me down a millisecond. I ground down a 9mm box wrench too for working on center pull straddle fittings.

* probably designed in for the manufacturer’s benefit, not ours