Defo p/n 42849-08 as I have a new one in the bag ready to go on.
thanks Ron for measuring the rear and confirming, i note its different p/n too. I know some other fasteners on the bike are imperial, its a real mix
I tried a 3/8 UNC thread insert as I had one of those kicking about from an old classic, it was so close i thought that was it, then when I fit the insert and screw the bolt in, its real tight, just not correct, screws in 1/2 way so tight im not looking forward to removing it
Anyway thats whats been in there since I messed it up last year. Now ive got a few months off work so figured I would fix it properly or get a used caliper and replace the lot.
So the mystery of the thread continues ....and the shortage of used LH calipers !