On the YZ we made a small solenoid operated valve that opened after 60% throttle, before the reed block. Ran a lean pre mix as well.
On my 360 I've got an oil pump (TS100 I think) feeding straight into the big end through the hollow crank shaft. Oil should leave/ fling off the big end and head for the cylinder and small end, mains sealed off.
On the DTPI Kawasaki, I just run pre mix as the injectors are in the crank case aiming at the transfer intakes. Seems enough oil is deposited to keep thing from going dry.