Yeah, a Vintage Spyder has no cable clutch like a Speedster. Disregard above comments.
The Spyder has a 5/8" master in the front and a 7/8" slave cylinder in the rear(usually, but sometimes people use different sizes).
I HIGHLY recommend flushing the fluid at least every two years. If it isn't done, and sometimes even if it is, then you will have problems. Sometimes you can disassemble the slave, clean it, and bleed and it's fine. Sometimes you have to replace the master or the slave.
Check and see if there are TWO nuts on both ends of the slave. If locknuts aren't used the nuts can back off and that could be your problem. Threads are 5/16" 18 TPI.
Be careful with blindly tightening the adjustment. Too much clutch throw WILL damage the pressure plate(over-extending the springs) requiring replacement.