Pre-mix ratio is 50:1. But pre-mixing went out in the 70's . Your way to rich at idle and slow speeds which may foul plugs, because you are burning double oil. Also the carbs will now have oil flowing thru them which will gum those up in time. I have owned over twenty two strokes that had oil injection with zero failures. Good luck with pre-mixing....I have a Kawasaki ultra 150. How many ounces of oil should I mix with each gallon of gas. It has an oil pump but I just don't trust them its easier for me just to premix. Thanks for the help!