Topic: Honda CB 750 no oil returning to oil tank

[Maddmaxx]

Hi guys,

I am working on a problem.

The oil does not return to my oil tank, I've filled her up with 3 qaurts and after a quick spin around the tank is bonedry?

I personally think the oil pressure relieve valve is stuck.

What could be going on?

Thanks in advance!

[PeWe]

Run the bike on the road for 20 minutes and you'll see oil in tank

[Swoop]

Did you do any rebuild work lately? Prime the pump?

Steve

[madmtnmotors]

Run the bike on the road for 20 minutes and you'll see oil in tank

NO! NO! NO!


Drop the oil pan and find the problem. A clogged screen caused the same issue for me:










The oil pump is fed from the tank. No oil in tank=no oil at bearings....

[fireman1073]

madmtnmotors what is that stuff? silicone?

[madmtnmotors]

madmtnmotors what is that stuff? silicone?

LOL!

I'm not exactly sure what it was. This was a bike that had sat outdoors for quite some time and IIRC the rear crankcase vent was disconnected. Seemed like mostly slime with a few odd bits of stray gasket material. Once the screen was cleared of all debris the engine performed flawlessly. This one experience has led me to drop the oil pan of every engine of unknown condition moving forward. 

[ekpent]

 Could be a problem somewhere. Also the bike should have around 3.5 to 3.7 quarts when full so an even 3 qts may be low.  I don't suggest it or do in anymore but back in the day when I didn't care as much I would just put in 4 qts and call it good.

[Maddmaxx]

I pulled the oil pump apart and noticed the rotors that scavenge the oil back to the oil tank were upside down.

The rotors themself were also heavily pitted and had a really hard time.

Could the upside down of the rotors have such effect on no return to the oil tank?

[PeWe]

The engine must have a history before then. Not getting the oil to flow into the tank after a few minutes of idling is how my bike have been after long storage, original pump let oil disappear really quick. But I knew and know it's OK.
 The pump will not become like that on its own. If engine has been apart and pump been taken apart by a not that careful mechanic, important to not run it. Replace pump with a pump not have been tampered with.

[markreimer]

I'd do a full pump rebuild at that point. A member here sells a kit, Elan. My oil light would flicker on at idle, I was having general oil pressure issues. I rebuilt the pump and bam! I've got loads of pressure now. The kit includes a new relief spring and seal.

[Maddmaxx]

I ordered a refurbished oil pump from Cycle X.

I hope this will solve the problem, if that doesn't work, I dont know where to look elsewhere.

Does someone has experience with these rebuild pumps?

[PeWe]

I pulled the oil pump apart and noticed the rotors that scavenge the oil back to the oil tank were upside down.

The rotors themself were also heavily pitted and had a really hard time.

Could the upside down of the rotors have such effect on no return to the oil tank?

My last oil pump refurbish had one of the rotors in a different way as I rembered from the pump before I run in my K6. I could not find out if it will matter or not. There is a punch mark on one side. I tried both ways and could not find any bad with either side. Both parts must have the punchmark on same side as I have understood it, not one of them flipped different.
I carefully sanded down the sharp scuffmarks that had a stick-out. Felt if it moved without mechanical contact.
Build here, scroll down a little bit more.  You'll see the restore kit from Vital
http://forums.sohc4.net/index.php/topic,168243.msg1958004.html#msg1958004
The X-bolts sucks. I replaced the 3 countersunk ones with countersunk allen heads, the other with hex heads

[rotortiller]

The reason for the punch marks is because they are lapped in when new for a best seal. This allows a best assembly condition when taken apart. The scavenge pump gear/rotor can be pretty ruff and still work seeing how it has such little restriction to work against. I'd carefully check everything in the sump area, tank, and lines.

[Jerry Rxman Griffin aka MuthaF'er]

madmtnmotors what is that stuff? silicone?

J E L L O

[madmtnmotors]

madmtnmotors what is that stuff? silicone?

J E L L O

P R I M O R D I A L   O O Z E

[Bodi]

I don't know what junk goes through the scavenge pumps but every used one I've looked inside (dozens) looked horrible. But still worked fine. Rotor direction doesn't matter, as long as the drive pin is in there it will spin and pump. How do hard chunks of get into the sump?
The pressure pump is more sensitive to damage, but except for what settles out in the tank, crap that went through the scavenge pump goes through the pressure pump too. You should match the punched rotor ends on the pressure pump. Those rotors never looked "virgin" either... but except for one phenomenally ruined rotor set (maybe someone dumped sand in the engine?) they worked well enough to have normal oil pressure. Maybe they would have too, but I scrapped them.
The gouges and such on the scavenge rotors, plus end play, will affect suction more than pumping ability. There's almost no resistance to pumping oil up to the tank. A badly scarred rotor set will probably have trouble priming if dry. Pouring oil down the tank filling line will oil it up. It might have more trouble pulling through a gunked up screen too.
If the tank is empty your engine is getting no oil. Don't run it like that!

[PeWe]

Sand or dirt in oil tank will do bad, right? Direct to pump, no filter. Particles from engine internals must be stopped by the strainer on the pump in the sump.

[Swoop]

What is the best method for removing the screen without damaging it?

Steve

[Henning]

A couple of small flat-bladed screwdrivers. You slide them sideways while pushing in until they bottom out, and then you can lever the screen out. Definitely doable with a bit of care.

[Swoop]

A couple of small flat-bladed screwdrivers. You slide them sideways while pushing in until they bottom out, and then you can lever the screen out. Definitely doable with a bit of care.

Thanks