Bought a RT2 from interstate which arrived today. Starts and runs just fine but I cannot ride it as I’m unable to select a gear with my foot. Had it up on stand and tried selecting by using my hand on lever whilst moving rear wheel. Ended up ringing Guy I bought it from and he said he’d not ridden it for ages but seemed to recall something about a spring and screw underneath the engine as maybe having something to do with it. Has anybody here got suggestions as to where I begin my search for a remedy ? Thanks

Ok, well if he is right he'd be likely talking about the plunger & spring which is 21 & 22 under a cap under the left side. Trans drain is further over & look similat but he might have drained the trans out the wrong one & lost the parts in the oil tray in dirty oil. That's a wild guess but would have difficulty selecting gears but is likely you'd find some gear but don't right as it'll jump out of gear if it does go in. so link below which is my first choice from how you describe things. But there'is more possibilities. Anyway 21-22
www.partzilla.com/catalog/yamaha/motorcycle/1972/rt2/shifter-a

second possibility is the shaft has moved sideways & got off the claw arm. But shouldn't be able to unlet the right side cover was off & something happened like bike fell over on the left--etc.www.partzilla.com/catalog/yamaha/motorcycle/1972/rt2/shifter-b

Third possibility is--trying to think lol--is spring 26, bit hard to read the number, it holds the claw arms up onto the pins & unlikely to fail or escape the arms.
www.partzilla.com/catalog/yamaha/motorcycle/1972/rt2/shifter-a

So--remove the detent bolt 19 that holds 21-22 in & see if they fall out--may not be in there. If they're in place then going to have to go in the right side cover & see if things are connected. Hard to read numbers but its No8 lever shift 1 & sits on 30 roller shift lever. Confused--yep me too. you'll need to hop between links to match up numbers & part names. Tis annoying eh!! just as the excitement starts--it's all over & replaced by "bloody annoyed".