TOPIC:

Good evening fellow Zedders,
The previous owner of the 1979 Z1300 that I've just got back on the road drilled and retapped the front calipers to take M12 mounting bolts. It's a nasty, poor job and I have no idea why it was done. The size of the bolt heads now required is huge and very, very ugly.
I was wondering if anyone happened to have a pair of the mounting plates as per the attached photo from some calipers that are no longer useful. I would consider buying complete calipers, even if they are otherwise junk, if I had to.
I'm located in northern Victoria, Australia.
Thanks in advance!

This is what happens when backyard mechanics don't know how to properly repair damaged threads and then go and butcher up a part that's no longer available. Shameful.

In order to use the 12mm bolts in place of the original 10mm x 44mm flanged bolts, thet must have opened up the mounting holes in the shock right? That will be your next problem.

What you might consider- 
To salvage the shock you need to bush the holes with 10mm x 12mm bushings in probably brass.

To salvage the mounting brackets, either Helicoils or tap lock inserts to restore the threads back to 10mm.

Just looking at the thread pitches for 10mm and 12mm. The 10mm is 1.5 and the 12mm is 1.75 so the helicoil won't work. A tap-lok insert might work.
I just wish people would know more about using helicoils for thread repair. They are quick and easy and if down the road a helicoil buggers up, you just remove the helicoil and screw in a replacement. Easy peasey.

Maybe you'll get lucky and scrounge up the mounting plate  but you'll still have to bush the shock.

Let us know how you make out please.

KB
  

100% correct, Kawboy.

You are spot on regarding the drilled out holes in the fork legs but I can get 12mm x 10mm tubular shims for them so I'm not stressed on that front.

I thought about Time-serts for the caliper plates (I haven't checked yet to see whether a Time-sert is available in a 10F thread) or even welding up the existing holes, machining the weld flat on a mill then retapping . I'm conscious that the the finished surface needs to be 100% flat and straight for proper caliper alignment.

Given that the fork leg situation can be sorted easily, a couple of (unmolested) mounting plates would be the easiest and best way out.

Thanks for your reply, Kawboy.