Top yoke centre nut removal?

Dumb question from a non-biking dad putting his sons bike (1999 sv650s) back together after a tumble. The bike hit the deck on the left hand bar and the bolt into the top yoke on left hand clip-on has sheared off. So need to get top yoke off to extract the sheared of bit of bolt.
All seemed simple, but I can't undo the centre nut on yoke. Should I be expecting it to be super tight? Am starting to deform the corners of the nut even with a ring spanner. Any tips from the bike-maintenance veterans out there?

If torqued correctly, that nut is 65 N.m. It should come off fairly easily.
However, someone without a torque wrench and no mechanical knowledge might have put it on, in which case, no telling how tight it is. They might have torqued it until it smoked.
At this point, use a six-point socket or spanner. A fairly large (1/2" drive) impact wrench driving a six-point socket is your best bet. A six-point spanner could work- apply pressure and smack it with a plastic mallet. Applying heat to the nut will probably help.

[squirrel_hunter]

I have seen a lot of rust on the threads on the yoke stem and top nut that has made removal more difficult then it should have been. I normally use a good quality correct sized socket on a nice long breaker bar. Go slowly and try some WD40 or Plus Gas to help. Heat can be useful here as well. Also if it is rusted I suggest a small tightening nip just to try and break the corrosion first.

WD 40, or plus gas, and heat are your friends here. get some lube in there, and get some heat on it, it'll help immensely.
6 point socket is a must.

yip, proper socket, plenty lube (soak it several times and leave it, then do it again). A good sharp shock released mine which was exactly the same - mallet if you've one, or I just stuck my shoulder into my breaker bar. If I remember right, I put something over the nut as it was a bit rounded - just to help the socket grip that bit more. Probably twenty reasons not to, but it worked.

MICK..

[jambo]

Now all the above is completely correct, and now you know it is stuck you'll want to get it off. But I've met a few Sv's with these little bolts sheared. If you got the weight off the front, loosened the clamp bolts and lowered the forks you can swap the clip on that way. And it doesn't need that bolt for anything but alignment, which you can do by eye.

Always good to have an option B.

Jambo

Sent without a real keyboard

Thanks everyone for the encouragement and tips. Awaiting delivery of a new socket to apply more force without risk of rounding nut, along with more lube. Though pretty sure it will not be overly rusted, the bike had barely been on the road for the first 10 years of its life.
But intrigued by Jambo's response - If it is safe without the alignment bolt then I may well leave it. I had kind of assumed it was more "structural" , or a least a fail-safe if the clamp loosened for any reason. I dont actually need to change the clip-on the damage to the bar was limited to the bar-end bolt bending and this little bolt shearing.
(The rest of the work is replacing the destroyed nose, headlight, front fairing frame, split in half clocks and repairing the splits in every other fairing panel!)

[Bibio]

block of wood placed on top of the nut and give it a whack with a hammer. this should loosen the rusted threads enough to take the nut off. or use a winygun.

[Sid Squid]

Jambo is extremely knowledgeable about the vagaries of SV construction and modification.

Had he correctly inferred from your post which part you were referring to he would not have written the post that he did, but he didn't, so he's utterly and absolutely correct - about a different bit of motorbike entirely.

[madcockney]

Originally Posted by Sid Squid

Jambo is extremely knowledgeable about the vagaries of SV construction and modification.

Had he correctly inferred from your post which part you were referring to he would not have written the post that he did, but he didn't, so he's utterly and absolutely correct - about a different bit of motorbike entirely.