Topic: Oil Pressure At Startup - The One Trick that Worked

[Wingnut74]

Spent all winter on a CB750 K4 total rebuild and today's goal was to try and get oil pressure and then test start. Poured quart and then some in the valve covers. Poured 10oz or so in oil galley part. Per HM's book, dunked the oil pump in bucket of oil and purged bubbles, but through all my monkeying around with timing and what not I probably turned it over 15 times manually and lost my prime. Installed nice oil gauge from cycle, many many 3-5 second bursts of starter with plugs out did not budge the gauge needle. Tried the compressed air in tank, nothing. Really did not want to drop oil pan because it was on a bike lift. Read a tip from fellow forum member to tilt bike over to the left, about 45 degrees then hit starter and whammo. Success! 60psi with starter and better once running. Never would have worked without the tilt.

[PeWe]

Oil pressure after a total tear down and rebuild is always very thrilling.
I have never had any problems with my CB750K6, opened it 4 times. Usually run on starter until lamp goes off. I never thought about filling oil pump when it had oil from before. Last time it got white spirit inside to clean the old oil of 20 years of no use. Maybe a little bit oil too, not only white spirit. This time other pump with less use I have had apart totally, new gasket, seal etc (Elan restore kit).

I filled the pump with oil and pumped around manually, rotate the sprocket with my fingers direct after assembly to ensure no corosion and not too much air inside.

I'll crank the engine with electric starter without plugs in until the oil lamp stop lit. I'll replace the oil pressure sensor too just for sure when the engine has got even more of $$$.
Some guys open the cap for oil path (where some mount pressure gauge) run with starter and see the oil flow to ensure a working pump.

[mystic_1]

The thing you are fighting on startup of a rebuilt motor is the fact that you won't see any pressure on the gauge until the pump has entirely filled the oil filter housing, the main oil gallery, and the vertical feeds up to the orifices in the heads. 

This is more volume than most people realize, and spinning the motor over with the starter is only, what, a couple hundred RPM at best on the crankshaft?  So you're not really developing much flow that way, this is why it can take a while to see pressure this way.  Many people say to just start it up and you will see pressure in a few seconds.  TBH I don't even really worry about priming the oil pump.

Putting oil in through the top (valve inspection caps) is a good idea but doesn't really help with time-till-pressure because that oil is draining down into the sump where the scavange pump picks it up and send it back out to the oil tank.

mystic_1

[Mr Freeze]

I can tell you that with an oil pressure gauge installed on a completely drained engine on a top end rebuild that it took about 15-20 for the pressure to register on the gauge. Since then it was fine, but you have to give it time to pump around for sure.

[KRONUS0100]

i always pack oil pumpss with petroleum jelly.......helps create suction and dissolves into the oil