CB750 F2 oil

[archmill]

Is this normal for a 750 F2 oil flow ?
Got the engine re-built and on a cradle on the workbench. Rigged up a temp oil tank (1 gallon clear bottle) with a simple flow and return piped and am turning the engine over with the starter. The temp oil container went down to nearly empty with tons of oil to the cams. Oil pressure at 45 psi. then oil appeared at the return pipe but the oil level stays down at the same level. Looks like there is as much flow as there is return.
Left the engine for 10 mins. and turned it over again. Lots of oil at the return and filled the bottle then the level dropped as before.
Is this normal for a 750 sohc, I.E. the flow is moving most of the oil into the engine and returns the oil to the tank on re-starting?
Never had a 750 before but it seems a bit odd to me.

[McCabe-Thiele (Ted)]

Would you not need a valve in the oil flow system or something to control the level?

[Bryanj]

If the engine is empty it needs to fill a bit before the return starts.
It says in the handbook to check oil level in tank after engine has been run and on mainstand i think, left standing oil will drain from tank into engine and get pumped back when run

[K2-K6]

General principle of dry sump is that the return/scavenge side of pump will always have more capacity than pressure, else all the oil would end up in the sump during running.

Pressure side MUST always have feed as that's the only route to fill oil galleries. The tank should NEVER be evacuated as its imperative to always keep that feed established and not allow air into the pump head pressure side.

After oil change on these 750, the filled tank will drop initially as it brings filter housing etc back to being full after change. Then checking to see what level you've got after that.

With cold oil though, you'll likely see variance (especially with clear feed tank to observe) as the thicker oil will take time to cascade back down to the sump after exiting the feed system through crank, camshaft chamber etc. The F2 more so in comparison to earlier 750 as they deleted half the drain back holes from the head to base of engine. If it's not reached the pickup, then the scavenge can't return it to tank for you to see there.

If you're not running it (getting oil warm) tgen it will look like you describe, especially with new oil at it's best viscosity characteristic. Leaving it to slowly collect back in sump will,then show increased return as scavenge pumpmhas it available immediately. 

This is different from in use "sumping" in which the oil is at correct level in tank at engine stop, only to leak from the tank perhaps overnight, to wrongly end up in the sump. It should have system protection to avoid this specific trait.

If you're not running it to get it warm, then that looks normal as described in first post. Letting it warm up should produce a competent and fairly equal level in the tank whether running or switched off after oil is at running temperature.

To emphasise though, the feed from tank should NEVER be voided whether hot, cold, new or old old, its the ONLY supply to bearings the engine has. There's no lubrication otherwise, all dry system are designed with tank  capacity and flow direction to keep this aspect as an absolute requirement.

[archmill]

Guys, cant thank you enough.
K2-K6 has certainly put my mind at rest. Didn't think along the lines that the oil is cold and thick (new) and therefore will take longer to get to the scavange side and return to the tank.
Can I ask is oil draining from the tank when the bike is sitting for a while a common problem with the 750 as I could fit a cock on the flow line but once new a guy who had done this and of course forgot to turn it on. Guess what happened.

[Bryanj]

Yes its common, there is an oil stopper in the oil pump supposedley to stop this but frequently it seeps and oil drains down.
If you leave it a long time drain the sump into a clean container and put it back in the tank, if the tank still has a reasonable amount in it just run the bike and observe the level in tank.

DO NOT fill the tank up then run it or you will get a large oily mess

[K2-K6]

My experience has never to be affected by draining down when stopped on a 750. They seem to be very reliable and effective without interference.

Some provisos, that the leak valve is in good condition and bike reasonably used fairly regularly.

Its properly engineered and placed, sits after pump head to always keep that primed, on its way to entering main crankcase gallery towards filter housing.  If it leaks, then it has to go through the pump, filter, galleries and out the crank bearings to drip down into the sump via that route. Its doesn't have a completely and gushing "incontinence" potential, that of dumping all the oil as soon as you've turned your back.

I dont say it doesn't happen, but correctly functioning then its reliable. I'd not introduce an additional valve to cover off something that does work reliablly.

There's definitely a risk with manual valve that I feel is significantly above the correctly operating std system. Same as you noted, with horror stories of people forgetting to open an oil "tap" on various installation.

Assessment, just check oil level when stopping and again after its stood, say overnight, then make a considered evaluation of existing system. The pump is very easy to work on if there's need to inspect and service the valve if there's a problem.

A mild "settling" after sitting will just be picked up by the scavenge side with not much to worry about.

[archmill]

Again, thanks guy's. Will constantly keep my eye on the oil level before starting after sitting for a while.