How much fork oil does the 1974 dt360 yamaha take?

My friend Dan and I have been working on vintage Yamaha's for over 10 years now. We know a good bit about different dt model's. We are not certified mechanics, so everything we know is from years of experience, and older generation riders experiences. My tip is about the Oil Pump that injects two stroke oil when you give it throttle. Last year i bought a near mint condition, 1974 Yamaha dt360. When overhauling the bike, my long time friend and riding partner Dan who owns about 5 different yamaha's, models from the late 60's the late 70's, suggested we disconnect the oil pump (clutch side) and drain all the oil out and pre mix the gas. Reasoning for this is he has heard numerous stories over the years about the pumps either seizing, or when you lay the bike over air bubbles can form which will then increase chances of the system not functioning properly causing the motor to seize. I kept mine installed on the bike, but disconnected the hose on the inside of the cover and drained all the old oil out, now I pre mix the gas. Thanks for reading.