You can indeed make your own tool to do it. Like most Triumph tools. I posted the dims of the Triumph tool years ago, could dig it up so people could make their own.
Someone said they used to run some gaffer tape around the inside of the sleeve and then manually turn crank so piston catches the tape and pushes the sleeve up.
I've only ever used the tool, as the first time I operated on one of these engines i didn't have time for any delays and had to be prepared with military precision.
Edit: found the old pics, please excuse the dark background
