Yamaha dt50r transmission is locked

I'm not an expert on the T-max, but universal transmission (gear oil) should do the trick. We use this on motorcycle chains as well.
700ml of SAE80 GL-4/5 oil
acc. to the link attached as well. SAE80 is usually used as gear oil (except automatic transmission fluid of which I'm unsure) https://www.louis.at/en/rund-ums-motorrad/bike-datenbank/yamaha-t-max-500-xp500/5gj1/1046

manual choke lever raises the engine reves to warm the engine by lifting the needle height and making the mixture rich, warm the bike up before moving off.

only 2 things will make the bike over heat
1 out of time du to slack in the timing chain
2 the fins are cloged a pressure washer will do the job

hope this helps you bob

on most coils terminals are + and _.12v goes on + and _goes to points