oil pump wet sump performance

NickZ

NickZ

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I've seen several threads on how to rebuild an oil pump with the objective of improving wet sump performance. While some mention improvement, I did not find any quantitative results which would indicate how much improvement is reasonable to expect, and / or how much wet sumping would be expected with a "good" oil pump.

I am asking because the 1973 750 Roadster I recently rebuilt wet sumps more rapidly than my other 750 Commandos even though the rebuild did include lapping the oil pump as suggested in workshop manual and elsewhere. At its 100 mile break-in check I took off the timing cover and measured how much oil came thru the pump to its output in 24 hours. The result was 150 mL. I then installed a brand new pump straight from Andover Norton. It passed 88 mL in 24 hours under equivalent conditions. This is more than a 40% improvement, which I am pleased to see, but I'm wondering how this compares to what others have measured.
 
I struggled for years with my 1970 750 wet sumping, it would leak about 200 ml per day. I reworked the oil pump several times, then decided to throw money at the problem until it went away. Fitted a new pump, and a Mk3 timing cover with the wet-sump mod in there and now I can't believe the difference, it doesn't seem to leak at all, I fill the tank to the right level, a month later, its still at that level, when the bike hasn't been started for a whole month.
 
Should add, I also fitted a new OPRV, in a kind of "maybe this will help too" moment, and the oil pressure is also much higher, I wish I'd done all this years ago.
 
NickZ said:
I've seen several threads on how to rebuild an oil pump with the objective of improving wet sump performance. While some mention improvement, I did not find any quantitative results which would indicate how much improvement is reasonable to expect, and / or how much wet sumping would be expected with a "good" oil pump.

I am asking because the 1973 750 Roadster I recently rebuilt wet sumps more rapidly than my other 750 Commandos even though the rebuild did include lapping the oil pump as suggested in workshop manual and elsewhere. At its 100 mile break-in check I took off the timing cover and measured how much oil came thru the pump to its output in 24 hours. The result was 150 mL. I then installed a brand new pump straight from Andover Norton. It passed 88 mL in 24 hours under equivalent conditions. This is more than a 40% improvement, which I am pleased to see, but I'm wondering how this compares to what others have measured.
Click to expand...
If you do a perfect job of servicing the pump, you will improve things. However, in that servicing you've done nothing to the gears themselves and other than changing them, there's nothing you can do to them. If perfectly lapped, oil won't go between the gears and covers, but that does nothing to make the gear mesh better.

The AMR mod or installing a MK3 timing cover are the only things I know of to stop wet sumping and neither of them is a guarantee.
 
I lapped my oil pump to try solve the wet sumping. My warm and cold oil pressures rocketed up. But it still wet sumps and that is ok for me!
I put in a Feker manual oil valve that electrically cuts the ignition power if the valve is closed
 
Just install a Holland Norton Works anti wet sumping valve. My Norton and 2 velos have no problems with wet sumping. Please explain what it is again please, i've forgotten. Graham
 
velo54 said:
Just install a Holland Norton Works anti wet sumping valve. My Norton and 2 velos have no problems with wet sumping. Please explain what it is again please, i've forgotten. Graham
Click to expand...
The only problem I have with those is there isn't any screen.
They say it is not needed, but if you run a crank-reed valve it can conceivably blow some contaminant back to the oil tank, bypassing the filter. I'm sure I don't want whatever that is, in my oil pump!
It is one thing to have something undesirable floating around in your sump - something much worse if it's sent to your oil pump!
I have one that I'll probably never use in my "spares" box.
Cheers
 
Rob, that's what you get if you fit a crank-reed valve. Dirty oil in your oil tank. But i don't think it would be a problem either way. Graham
 
Oil can also leak through the pre-Mk3 OPRV or along its threads as the oil from the OPRV is sent back to the inlet side of the pump so has a connection to the oil tank.
 
Oil that goes over the OPRV should go into the timing chest and back to tank via the scavenge pump, so that the pump is always fed 'fresh' oil from the tank. I modified mine ['72 750] to do this. Easy enough to do but i can't remember what i did exactly. Must have plugged one gallery and drilled another one. Graham
 
Crankcase plug

oil pump wet sump performance


Cover mod

oil pump wet sump performance
 
robs ss said:
The only problem I have with those is there isn't any screen.
They say it is not needed, but if you run a crank-reed valve it can conceivably blow some contaminant back to the oil tank, bypassing the filter. I'm sure I don't want whatever that is, in my oil pump!
It is one thing to have something undesirable floating around in your sump - something much worse if it's sent to your oil pump!
I have one that I'll probably never use in my "spares" box.
Cheers
Click to expand...
I've seen it happen on a Combat that wet sumps and you first run the bike: it contaminates the whole oil system with debris, when contaminated oil is returned via the Combat breather because it is on the lower base / engine cases. Small Aluminum and metals, ect. gets into the oil tank, then gets into the oil pump and then it even gets into the sludge trap. Not Good! In my case it was fine flakes of aluminum. If your bike does not have an oil filter. It would even be worse.
 
robs ss said:
The only problem I have with those is there isn't any screen.
They say it is not needed, but if you run a crank-reed valve it can conceivably blow some contaminant back to the oil tank, bypassing the filter. I'm sure I don't want whatever that is, in my oil pump!
It is one thing to have something undesirable floating around in your sump - something much worse if it's sent to your oil pump!
I have one that I'll probably never use in my "spares" box.
Cheers
Click to expand...
If ‘dirty’ oil from the sump entering the tank via the breather worries you, you might wanna look at one of these, virtually no ‘blow through’ resistance (and made in Oz):
oil pump wet sump performance
 
DennisMo said:
I lapped my oil pump to try solve the wet sumping. My warm and cold oil pressures rocketed up. But it still wet sumps and that is ok for me!
I put in a Feker manual oil valve that electrically cuts the ignition power if the valve is closed
Click to expand...
“Feked”, a supplier of British motorcycle parts.
 
MichaelD said:
I struggled for years with my 1970 750 wet sumping, it would leak about 200 ml per day. I reworked the oil pump several times, then decided to throw money at the problem until it went away. Fitted a new pump, and a Mk3 timing cover with the wet-sump mod in there and now I can't believe the difference, it doesn't seem to leak at all, I fill the tank to the right level, a month later, its still at that level, when the bike hasn't been started for a whole month.
Click to expand...
Thanks for this data point. 200mL per day is a good bit more than I had.
 

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