Dont you drain the lot just stick a new litre* in and thats it?
*I think it was a litre on the racer. I know I only did it once to measure it then threw away the filler spout and dip stick and used a shallow plug in the crankcase thats a few ounces saved proceedure than was to drain and fill up every meeting or so keeps an eye on the oil contents that way as well
*I think it was a litre on the racer. I know I only did it once to measure it then threw away the filler spout and dip stick and used a shallow plug in the crankcase thats a few ounces saved proceedure than was to drain and fill up every meeting or so keeps an eye on the oil contents that way as well