1977 Questions for all other cars 1977 Yamaha 750 Motorcycle

Transmission problem
1977 Questions for all other cars

I have a 1977 Yamaha 750 3 cyl Motorcycle, and whenever I need to change gears I have to reach down with my hand and without using the clutch, repeatedly slam the shifter to get it to catch the next gear. I don't have a repair manual to refer to for information on what might be causing this, or to show me which side of the motor to tear down to see why this is happening.
Also, there is something loose in the transmission, I don't know what, but I need to see an exploded view of the transmission, to see what it might be
and where whatever it is would maybe go?