Twitchy

Hey all, I'm new here and lookng for some help. i have an 88 fz 600 (not fzr, just fz, no genesis head etc) I bought it last september in pieces from a guys garage who couldn't get it back together. yesterday I finally had it started up and revving well, the problem is in neutral it started and revved, (it's on a swing arm stand) but when i clicked it into first to test the tranny, the back wheel started spinning, clutch pulled in and all. I have other old bikes that do this too so i stuck my foot on the tire to stop it, but it wouldnt stop so i can only think that the clutch was engaged, so i id what i could to shorten the cable and even manually held the spring loaded pull all the way so it should be disengaged. same thing. Now i have had it since september, and moved it from chicago to phoenix (yes it spend a few months in a storage unit with no climate control), i changed the oil/filter, but i don't know how long it sat before i got to it, the guy told me he tore it down the summer of '09 but no way to confirm. I was reading my manual and it tells me the clutch plates could be warped (or steel rings) that keep it engaged and keep the wheel turning. before i go tearing into the clutch, I was hoping for other ideas. also it should be known that the clutch pull is very easy, usually there is a good grasp needed (my other bikes need a firm hand) but this is less than half the effort needed. could that be something? it is a new clutch cable (old was rusted and stuck) I appreciate any help thanks