Extra tubing inside frame

Hi,

I've cut the rear of the frame to weld on a loop, not too much cut off to start with, but it looks like the frame is made up of two lengths of tubing, with the OD of the inside tubing being tight on the ID of the outer frame tube.




I can't find anything that references this except a very brief blog post here...

http://www.chinonthetank.com/2013/01/how-to-cb750-rear-frame/

I tried to get a chisel on one, as per the advice in the blog, and see if anything happened when I hit, but it's pretty determined to stay in there. I'm not even sure how far it goes? The only other idea I have is about making a small cut around the frame half an inch in and knocking off the outer frame tubing to expose the inner?

Does anyone have better advice on how to get it out?

it would be a miracle if you could separate that ,why are you needing to do that ? if yer welding on a hoop just get r done no need to mess with it further
just be sure and think ahead,leave room for the rear tar when the shocks are bottomed out

Fairplay. I was planning on using a plug so wanted to get the ID of the frame and the loop the same. May just butt weld it then... or if I can be arsed, make a stepped plug instead.

Cheers for the reminder of the tyre clearance. I have a kick up on the loop and will be fitting a rear mudguard to it, so the clearance of that to the tyre will be important. I haven't got the foggiest what the maximum travel of the shocks will be?

pull off one shock set the other spring soft and ratchet strap the shocked side down hard, observe,measure, make good memory

If the 2 pieces are not welded together take a hack saw blade/jigsaw and cut a slot in the inner tube to relieve the pressure on the outer tube and pull it out.