Topic: Oil consumption or/and worn oil pump? '76 CB750F WITH VIDEO

[HondaNorway]

My '76 SS uses a portion of oil, and when I fill it up again (on hot engine of course) and run's it for a while, then it's too much. I don't refill anything more than a couple of deciliter. Could it be that the oil pump is worn, so that the oil don't get pumped back into the oil tank? I can't find any major leaks on the engine. The bike ran with too much oil earlier this summer, can this hurt the engine badly? Or be a reason for the apparently oil consumption?

I check the oil when the bike is on the center stand.

The bike run's strong now, but when I was on a roadtrip for a couple of weeks ago, the engine felt weak after 1-2 hours on the highway. Hard to explain  

-Stian  

[Bodi]

Check the oil level immediately after the engine has been running.
There's a check valve in the scavenger pump that takes oil from the sump up to the tank. This check valve often leaks slightly (occasionally a lot) letting some oil drain back into the sump with the engine stopped. This is not a big problem, the tank can't drain back completely since the return line is not at the bottom. It just means that checking oil level after the bike has sat for a while will be inaccurate. Sometimes one can add enough oil that it comes gushing out the filler on startup.
The check valve can be inspected and cleaned but the little rubber insert that actually seals it is unavailable, so basically you live with it.
It's not likely that the pump is worn out. The scavenger pump section (it also lubes the transmission) is quite large and works against very low pressure. I've seen remarkably bad looking scavenger pump rotors that work fine. The engine pressure section of the pump is much more likely to have symptoms of wear, easily checked with a pressure gauge on the main oil gallery. It's possible for a really badly worn out engine to have clearances so wide that a brand new oil pump won't maintain sufficient pressure but that takes a lot (A LOT!) of miles or a lot of abuse and I think the engine would sound very rattly.

[Jerry Rxman Griffin aka MuthaF'er]

Hondaman will have a NOS "check valve rubber insert" in his hands soon to hopefully produce an alternative part. Check in with him. The part probably will not be here for 3 weeks. Someone(s) brought the other 6 available on EBay. Can anyone own up to this? I got the last one the guy had (Thailand) and I also got 4 nos springs.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=310233825654&viewitem=&sspagename=ADME%3AL%3AOU%3AUS%3A1123

[HondaNorway]

Check the oil level immediately after the engine has been running.
There's a check valve in the scavenger pump that takes oil from the sump up to the tank. This check valve often leaks slightly (occasionally a lot) letting some oil drain back into the sump with the engine stopped. This is not a big problem, the tank can't drain back completely since the return line is not at the bottom. It just means that checking oil level after the bike has sat for a while will be inaccurate. Sometimes one can add enough oil that it comes gushing out the filler on startup.
The check valve can be inspected and cleaned but the little rubber insert that actually seals it is unavailable, so basically you live with it.
It's not likely that the pump is worn out. The scavenger pump section (it also lubes the transmission) is quite large and works against very low pressure. I've seen remarkably bad looking scavenger pump rotors that work fine. The engine pressure section of the pump is much more likely to have symptoms of wear, easily checked with a pressure gauge on the main oil gallery. It's possible for a really badly worn out engine to have clearances so wide that a brand new oil pump won't maintain sufficient pressure but that takes a lot (A LOT!) of miles or a lot of abuse and I think the engine would sound very rattly.

Where is the main oil gallery located? And what range do the pressure gauge need to be (0....x bar)?
Btw, do I really need the engine breather filter? It comes small amounts of oil, and sometimes, after driving longer distances, smoke from it.

Thanks for great answers

-Stian

[HondaNorway]

It comes oil/smoke out of the engine breather filter on my bike
Here is two videos so you can see

http://www.youtube.com/watch?v=Ev66d_utLbo

http://www.youtube.com/watch?v=Hp399ZAisos