Just stripped my 3EN2 for a total rebuild and had no problems with any nuts/ bolts seizing apart from the chain adjuster bolts in the swingarm.
They both sheared flush with the threaded blocks. Anyone had any experience with this problem. Any advice would be good as the swingarm is in great nick.
Also, I am looking for some 41mm forks as mine are knackered. Will any other yamaha ones go straight in with no mods.
Thanks in advance

Those adjuster bolts are mild steel originally and the threaded portion of the s/a is quite long.
Folk never take the bolt right out to copperslip the threads, nor do they spray lube up into the inside of the s/a through the water drain hole directly at the bolt from the underside.
No wonder the adjuster seizes.

Next time, if stiff get some heat on the bolt before shearing them off.

You can get easy access with a long drill bit to bore out the remains.
Go up sizes in stages.
See if you can get a reverse 7mm bit to use last; it may turn out the remains of the thread.

Replacement forks will require additional parts/work.
You will also end up with 2/3 inches of stanchion up through the top yoke if the ride height remains as original.
Stanchions can be rechromed economically.

You can fit 600 Foxeye or Thundercat front end but you need the wheel because the spindle size is different.
I changed the adjuster bolts on mine to stainless - not much help to you now. Maybe take it to an engineering company, they can use a pillar drill etc.

Thanks for the advice gents

Regarding the forks, I can get a 3TJ set with bottom yoke. These are 43mm. Will they be a direct replacement if I get the top yoke bored out. Is the headstock/taper bearings/wheel spindle & spacers the same.
Thanks

The 3TJ forks are shorter than the 3en forks, the spindle / front wheel is the same as the 600 foxeye and the brake calliper bolt spacing is different too. You'd still need the front end and the standard 3TJ RR forks aren't adjustable, you'd be better of with the T'Cat or Foxeye