I had 3 2-strokes, Bridgestone 350GTR, Yamaha R5 and Yamaha RD350. They all had oil injection and it always worked flawlessly.
Having said that, the ignition from that era (early '70s) was rather anemic, and a 2-stroke needs all the spark it can get. The symptom is short plug life before fouling. If your bike has points/coil ignition, you might try an automotive or some other ignition coil, with a ballast resistor to limit current thru the points - I did this on the RD350.