1979 440 Exciter gas to oil ratio

[Snow Chaser]

I bought a 1979 440 Exciter and the oil enjection is not working.
Since this is my first vintage Yamaha, I want to try to make sure I don't hurt the engine.
So, my question is;
What oil would you run in it and what would be a good ratio of oil to gas to run until I get the injection fixed.
Any comments and info is greatly appreciated.

 

[SWEDE]

With modern oils I'd run it at 50:1 and Yamalube or whatever would be fine.Back in my pre-mix days I ran Valvoline 2 cycle which was available pretty much everywhere.My first sled was a quart of that to 5 gallons of gas, kinda smoky lol!