grab the exhaust and twist it as best you can, better with someone holding the downpipes to stop them breaking.
Spray some wd40 where exhaust and downpipes touch.
https://www.youtube.com/watch?v=cLWFJ1f92Ac
Bit old now but this was a 2nd hand Delkevic one on the wife's FZS600 (which I used too as it sounded greeeeat!) 8)
'Still lazy, after all these years'.
Well it's slowly feeling like there is some progress. I'm now at a stage where I'm having to scrape out a load of silvery crap from the join. I'm assuming this is sealant from before? Anyway, keep soaking it in wd40 and trying to twist it. Hopefully there will be some progress tonight, otherwise, I recently joined the Oval Motorcycle garage where you can book in to do work and a mechanic will help, so maybe i'll pop there sat morning and get some assistance.. .Just want the new exhaust on now!!