Can't say for sure if it's the original plug, but it is 13/16ths. My main worry is hitting to hard, and crackiing the case.
The young man who has made me a number of alloy tanks over the years is good at this sort of stuff, so may well give him a call tomorrow.
Does he have a TIG welder? I did this one a while ago.... it was in something important, so was sweating bullets setting it up, so the drill would be centred and not take out any threads. Works well for small stuff, but with the flange on the drain plug it takes more than these guys to budge it. If he bevels the end of whatever he welds on there, then you can sneak in there and get reasonably good penetration on the backside. Donít think I would want to use anything other than TIG. Easier to control things and actually see whatís going on. Either way good luck... it is gratifying when the little bastards come out without any drama.
If you lived closer, I could fix you up with a NOS rim, but the catch is itís amongst a bunch (all unlabelled) and you might go mental figuring out which ones are drilled for conical hubs.
Not sure what the previous owner was thinking regarding the wheels. Both have stainless spokes fitted, the front rim has been replaced with a newish Hagon, the rear rim however looks to be original, and is as rough as a Badgers arse.
:cool: Could be worse, Anteater has a way nastier ass then a Badger.
Should have been a reasonably straight forward job removing the swinging arm, but the pivot's locked in solid.
I've tried heat, and brute force to no avail.
Can you cut the head off the bolt and drive it through the rest of the way ? bolt must not be anything exotic or it wouldn't have rusted to begin with.
I've had pretty good luck freeing rusty pins with a heat gun and penetrating oil. You would need to lay the bike down, heat the swing arm and dab penetrating oil, with a paint brush, where the pin protrudes. It should suck the oil in just like solder would.
Looking at the overall condition of the bike I'd say it's been ridden through a good few winters. Every nut, and bolt seems to be putting up a bit of a fight.
Just out of interest I checked the MOT history. Turns out to be a 1977 model, original colour was blue. Last MOT was 12 years ago, and since 2006 has covered the grand total of 5 miles.
Looks as though the mileage of 11922 miles is probably genuine.
About 10 years ago I had a similar issue with a front engine mounting bolt on a R100. Ended up having to cut through the bolt, and take the engine to an engineer to drill it out.
Riding through UK winters doesn't do a bike any favours.