Topic: wet sumping

[H2 frankie]

I have a K1 CB750 and I have noticed that the oil in the tank soon ends up in the sump.
The bike has been dormant for a good few years and I am attempting to resurrect it
I assume there is a valve somewhere that is stuck open near the oil pump
Is this work that can be done with the engine in the frame?
Thank you

[Steve_K]

I have a 73 750K and it does that after the riding season is over.  Mine does work ok when ridden often.  Change the oil and that may help.  There is a check value on the bike, but I am sure there are some posters who have replaced it.
Steve

[70CB750]

If you can drop the oil pan, you can take pump out.  Elan - member here - sells parts to fix your problem

[Davez134]

I have a K1 CB750 and I have noticed that the oil in the tank soon ends up in the sump.
The bike has been dormant for a good few years and I am attempting to resurrect it
I assume there is a valve somewhere that is stuck open near the oil pump
Is this work that can be done with the engine in the frame?
Thank you

Yes, there is a oil stopper valve in the pump that prevents flow from the tank when not running. There is a member here who makes (or made, not sure if he still does) replacement rubber stoppers. Very easy to replace. Unbolt and drop oil pan, remove 3 bolts holding in oil pump and take it out. Download the free Honda service manual from this site for specifics.

[H2 frankie]

Thank you for your help everybody

[Don R]

 You gave good information and asked a well thought out question. That helps a lot.

[PeWe]

Oil pump restore kit.  Same as ELAN's?
http://www.ebay.com/itm/Honda-CB750-oil-pump-rebuild-kit-SOHC-oring-stopper-seal-/162018691768?hash=item25b9110ab8:g:uTMAAOSwubRXG83p&vxp=mtr

+ oil pump pickup strainer (David silver sells it too, Honda that has slimmer rubber seal.)
http://www.ebay.com/itm/1969-1978-Honda-CB750-oil-pump-sump-pickup-strainer-SCREEN-SOHC-/162055123874?hash=item25bb3cf3a2:g:10IAAOSwiYFXJOzo

Edit: My bike had that from the very begiinning when I bought it 1979 with 17.000km. Oil level in tank sank during the night. I heard that it was typical CB750.. Had never any issues with it. Learned to check oil level after the bike has warmed up and 10 minutes ride.
3.5 liter in when engine was restored and no oil. 3.0 liter at a oil change to start with. Adjust after a ride.

I replaced the pump with another with half use than my ol with 100.000km. Elan's kit in it and oil level stays. I have another "problem" now when draining oil when lifting the engine.... >2 liter in tank was new for me, old 1.5L coke bottle overfilled and floor got oil....

I ordered a new kit above from eBay for my other engine build.

[flybox1]

Oil pump restore kit.  Same as ELAN's?
http://www.ebay.com/itm/Honda-CB750-oil-pump-rebuild-kit-SOHC-oring-stopper-seal-/162018691768?hash=item25b9110ab8:g:uTMAAOSwubRXG83p&vxp=mtr

+ oil pump pickup strainer (David silver sells it too, Honda that has slimmer rubber seal.)
http://www.ebay.com/itm/1969-1978-Honda-CB750-oil-pump-sump-pickup-strainer-SCREEN-SOHC-/162055123874?hash=item25bb3cf3a2:g:10IAAOSwiYFXJOzo

Edit: My bike had that from the very begiinning when I bought it 1979 with 17.000km. Oil level in tank sank during the night. I heard that it was typical CB750.. Had never any issues with it. Learned to check oil level after the bike has warmed up and 10 minutes ride.
3.5 liter in when engine was restored and no oil. 3.0 liter at a oil change to start with. Adjust after a ride.

I replaced the pump with another with half use than my ol with 100.000km. Elan's kit in it and oil level stays. I have another "problem" now when draining oil when lifting the engine.... >2 liter in tank was new for me, old 1.5L coke bottle overfilled and floor got oil....

I ordered a new kit above from eBay for my other engine build.

Yes...that is ELAN's kit in the first ebay link.  IIRC, he also makes the strainer.
Great product.