Fork oil weight

I am preparing to change the fork oil and seals on my 1982 KZ550 A3. My manuals say to use SAE 5w-20 oil, but I've noticed that fork oil is weighted differently from motor oil (5w, 10w, 15w, etc). Is it better to use dedicated fork oil, and if so, what would be equivalent to 5w-20?
Thanks!

I suggest 10 weight fork oil.  And consider getting new fork springs which don't require any air to supplement the for springs.  You can use 15 weight if you are a large rider and/or if you carry a passenger regularly, but the ride will be less compliant.

I'm not a very large rider (6'2" 170lbs) so 10wt sounds good to me. Why do you recommend replacing the springs rather than adding air pressure?

wrote:

I'm not a very large rider (6'2" 170lbs) so 10wt sounds good to me. Why do you recommend replacing the springs rather than adding air pressure?BB

Because the pressure leaks down and causes stiction on the seals.  Get yourself some nice Sonic springs and problem solved for a nominal price.

Interesting, I'll look into that.