Wayne wrote:

A friend of mine (really!) went to remove a mirror
from his motorcycle. The mirror mount is steel and
mounts to the front brake master cylinder (aluminum).
There is a recess in the mirror into which an allen
head bolt holds the mirror to the master cylinder.
He broke the allen wrench flush to the top of the
bolt. The head of the bolt is recessed to where
you can't get at the sides of it. The bottom
of the bolt is visible on the underside of the
master cylinder.

The only way I can think of to fix this is to
take the master cylinder off, turn it upside down.
Then drill through the bolt from the bottom side.
Then take a punch and knock out the allen wrench.
Then use an impact to take the bolt out.
We'd have to fill the master cylinder full first
so air doesn't get into the line when flipping
it over.

This sounds like a lot of work. Anyone have any
easier suggestions?

His original problem is the mirror keeps loosening
up on the 'stalk'. The ball on the 'stalk' is ridged.
That sits in a plastic piece. By moving the mirror
you can see where the plastic is falling apart in
the ridges. He's already replaced the mirror several
times. Is there any kind of goop that could be put
in there which would hold the mirror, but still
allow movement?

Wayne D.

I don't see where you have anything to lose by trying your favorite real
penetrating oil, a couple of gentle heat cycles, a left-handed drill bit from
the top (or remove the master cylinder and use a RH drill from the bottom) and
try an easy-out.

Another trick I like is to make a little square of sheet metal about the size of
a postage stamp, punch a hole in the center, and plug weld it to the end of the
bolt (using O/A or MIG or however you can) then welding a nut to the sheet metal
and using the nut to turn out the bolt. Might be tricky with the seals in the
master cylinder so close, though.

Steel bolts frozen to aluminum can be very tough indeed. My guess is you'll wind
up using a helicoil or equivalent, or maybe buying a new master cylinder.

My guess is this motorcycle isn't a BMW.

GWE