Working on my son’s YFZ450R. Recently replaced piston and cylinder. I put 2 quarts of oil in the crankcase. I started it and let it warm up for several minutes. I turned it off and checked the oil on the dipstick. No oil is showing on the dipstick. There are no external leaks. Where did the oil go or why is it no showing on the dipstick? This is an R model it does not have a separate oil tank.