I have a 68 BSA A65 bobber and I have a question about the oil sump. I put oil in the reservoir tank and bring it up level. I can see in the tank when it is running that there is a good flow back to the tank and that the top end oil line has a good amount of oil going to the lifters. I took the sump plate off and no oil came out. I removed the valve cover and put @ 1/2 qt of oil and the oil started to raise the level in the reservoir tank. Is there not suppose to be oil staying in the crankcase area of the engine? Maybe a dumb question, but the manual didn't say drain the oil when you take the sump off.