Originally Posted by
Biker Pete
... for fear of stripping the bolt head.
Originally Posted by
Barry2
OP is worried out rounding out the Hex, not twisting the head off.
Right; apologies all'round for my misread.
Originally Posted by
Biker Pete
A 6mm allen wrench ‘wiggles’ a bit too much and I can’t apply a large amount of torque for fear of rounding out the aperture in the bolt head. 7mm and 1/4” wrenches are slightly too large; 7/32” wrench is too small. It’s meant for a 6mm wrench but unfortunately when I received the bike the bolt head aperture was already slightly buggered.
Yep, those pics show that clearly.
Too, it's possible that there's
so much rust around and under the head of that sunken Allen head you're not getting much (if any?) penetrant down where the threads that need it live.
Also possible that whomever installed that stem didn't use a split lock washer underneath the bolt head, why it might have been overtightened & why also what's left of space under bolt head & stem bore is rust filled.
Barry2's suggestion of using a Torx tip is a good one, if you have one that'll fit tight into that buggered hex bore.
Torx 40 measures 5.76mm across
pairs of tips, 6.47mm across
opposite points. Allen 6mm measures 6.72mm across opposite points; 7mm Allen measures 7.89mm across opposite points.
Making
sure your Allen tip is square and 'sharpish' at the end is a really good idea! This
isn't something to attempt with a ball-end wrench.
(Take a moment (if you would) to wick out the penetrant in that buggered Allen bore, take another pic of it dry, post it here. I'm curious what shape it's presently in.)
A 7mm Allen tip, slightly 'modified' with a stone on a bench grinder or Dremel may be the ticket. You want whatever tip you deploy to bottom out in the bolt head's socket, and if the fit is tight enough (why the modifying) to bite into what's left of the corners it ought to come free with an impact tool.
Leaving your hands free to apply forward pressure while the impact does the twisting's the key here. This isn't something you want to try using a simple L-shaped Allen wrench alone.
Originally Posted by
Biker Pete
P.S. In an ideal world I’d like to raise the stem by about 1/2” but honestly, I can live with it the way it is. But it bugs me that something is f’d up on this otherwise BEAUTIFUL and AMAZING Serotta Legend Ti bike!
Yeah I feel your pain there. That's a beauty you've acquired!
Once you've succeeded in getting that stem free, do a thorough inspection of the steerer tube inside and out please.