Man_Named_Dave wrote:

thunderace wrote:If you have access with a drift, hammer a Torx bit in there. Should do the trick if the head is fubar

That is by far the best way to remove a rounded hex head!

Man_Named_Dave wrote:I'm having trouble trying to tighten the top bolt/nut going through the top of the rear shock.

I put a hex fitting onto a ratchet (coming from the left-hand side) to stop it spinning, but the nut feels like it's just rotating rather than tightening. I got some tension on the torque wrench but it just disappeared when I kept turning. I'm assuming the nut and bolt are completely shagged?

Cut the nut off by cutting a groove on one of the flats with a junior hacksaw and split it with a steel chisel there's not a lot of room to work in I know but once nut removed in some manner you should be able to drift the bolt out easily enough, then pm me your postal address. Got a spare top bolt n nut in shed can stick in post free gratis. P's don't clout the frame mount whatever you do take your time.

As Dave (Arsey) says, it seems unusual for it to be the bolt, but that does appear to be the case. I just tried again with an 8mm Allen and 17mm open spanner and it was just rotating, not un-threading itself. I undid the bottom shock bolt in case that was causing an issue but it made no difference.

I'll see if I can manage Dave (Trucker's) suggestion, although I think it may be worth trying with a rattle-gun.

I am not sure if there is room, but if the thread is stripped, then try wedging a screwdriver blade under the nut and turning the bolt.
Sometimes it will drive the nut up the thread until it finds a good thread.
Depends if nut or bolt thread has gone, but worth a go, keeping a leverage pressure on the screwdriver/nut.

This bolt should be an Allen bolt with 16mm ground head that locates in the frame on the left side. Rather use Honda part or machine a standard bolt to the correct diameter. Take care removing the old nut and bolt as if you damage the holes in the frame you will end up will play in the suspension.

From memory is this not 14mm not 17? The bottom one is 17. Try pitting the bike on it's wheels to load the suspension as this will hold the bolt, and get someone to sit on it.