Honda engineer
CB750 Member
How much oil should remain in the crankcase of my CB750 K5 after I shut the engine? It runs fine and has 75 psi oil pressure
Oil level in crankcase
- Thread starter Honda engineer
- Start date
All of it, minus the oil in the valve train and clutch area. Kind of a weird question, why do you ask?
Honda engineer
CB750 Member
Being that this is a dry sump, I have never thought that there would be any oil in the crankcase when the engine is shut off. Some years ago I ran into a case where all was in the sump. Turned out there was a problem with the check valve on the pump being stuck open. I drained the oil in the dump on the K5 and there was 800ml oil oil in the crankcase and I was wondering if this is normal or should check the check valve on the oil pump.
Honda engineer
CB750 Member
I have previously run into a problem with all the oil remaining in the crankcase. The problem turned out to be a frozen check valve on the oil pump. I checked the crankcase and found 800ml there after I shut the engine off. I wonder if this is normal.
Interesting. You appear to know these bikes, better than me. I'm about to learn some stuff, i think!
If the checkvalve in the pump is working about 1/4 to 1/2 quart is ok. After you shut the engine off there is still oil in the top end and in the oil galleries that will run down into the sump. It is normal for oil to leak out of the tank after sitting for extended times...weeks or months. After new check valve seals they normally dont leak down any oil unless it sits for many months, they all will leak down after long periods even with new parts. If the tank runs dry in a week you have problems....couple weeks, probably still a problem, month or more then it just becomes a pain to deal with it. If the tank runs completely dry drain the engine and fill the sump before cranking. If the tank is dry and you start it to pump the oil back to the tank you will have no oil to the engine for quite a few seconds, you will cause excessive wear guaranteed. People say they have done it and never had an issue but they are causing damage, you cant run an engine without oil and not cause damage even if its for 10 or 15 seconds.
