hello everyone, I have an issue that I can seem to resolve.  I replaced the clutch plates on my GT80 and after putting everything back together, the clutch doesnt want to disengage.  I readjusted the clutch cable and little screw on the cover by the mag cover to get it as tight as possible but the clutch doesnt want to disengage the plates.  The lever is tight, and it seems to move but am wondering if there is a something I missed.  I looked at the parts diagram am it seems like everything is assembled properly, so I was wondering if there is a trick or something that I am missing?

Greetings from Tennessee 
  there is a ball that goes between the 2 clutch rods. They seem to magically disappear usually in your oil pan that’s the first thing I would check

When you replaced the plates did you operate the clutch to watch the pressure plate lift. Does it feel like the lever is lifting it-- like, takes pressure to squeeze the clutch lever. If all that is operating, i'm lost sorry. Do you mean you start it & put in gear then it takes off--can't stop.
Actually HT1KID above makes sense as i think the ball can roll out if you had the mushroom piece out.although there's no need to remove that to change the plates. Just hope its not dropped between the basket fingers & gone hiding in the motor.

#16 goes between 14 & 17
www.partzilla.com/catalog/yamaha/motorcycle/1975/gt80b/clutch
Also, have you had the center nut off for some reason while changing the plates as might have another theory.

Thank you so much everyone, I downloaded the service manual from this site and it showed 2 thrust plates (washers) and from what I recall, I only had one that I put back on the clutch basket when I reinstalled everything. They should arrive today and I'll see if that is the issue, otherwise I hope that the ball thing didn't happen....

From the parts diagram it looks to me like there is one washer on each end of the long spacer (#4 x 2).  Those washers would have the same ID as the long spacer and the long spacer would butt against them.

Then there is one washer (#3) that has an ID that fits over the spacer.  I would call that the "thrust washer" but I guess all three could be considered thrust washers.

Good news, it is now fixed after I installed the new "thrust" washers, but I believe my issue was that I flipped around washers #3 and #4 in the assembly after the clutch boss into the clutch assembly. So I installed them as the diagram shows and now, I have my clutch back! Thank you to everyone that replied and gave me guidance, I genuinely appreciate your help.