My progressive springs will be here very soon.I have an 1989 GS500.I did a search
and found out about using a long bolt to extract the inardes of the fork.I am
rebuilding my forks.Will this method work?Can I use the 5/16 bolt or do I need
another size?Thanks
Ben

I belive that it's a 5/16" size with the head 15/16" so it uses a 15/16" wrench. I used a piece of all thread with two nuts jammed up against one another on either end. Or you could use two bolts put together with a coupling nut.

OK.Here is what I bought to make the tool.It cost $9.71US from Lowe's.
I bought 2-5/8 bolts 10 inches long and one 5/8-11 coupler.I read here
and have been told that the head size is 15/16.If you have doubts
when looking for the right bolts,just take a 15/16 socket with you.I
did and checked the heads of the bolts for tightness in the socket.I put
five back in the bin because they were loose in the socket.Don't wanna
reach down deep in the fork just to realize you screwed some thing up
with a bad tool.

Instead of 15/16" try 24mm. Every fastening on the bike is metric.

I used 15/16" and it worked fine for me.

So far it's working like a charm.