Oil pump testing

Hi all,

I'm restoring a basket case "74 Commando and am wondering how I can assess the effectiveness of the oil pump when it is not installed. I'd appreciate the wisdom of smarter people than me

Paul.

Really as long as they turn and have most the teeth still intake, they work fine. Mostly the spiff ups are to stifle the wet sump of sitting up.

I sorta test mine by filling with oil and watching where and how much spits out on spinning. Otherwise - oil pressure gauge, which likely measures engine clearance and temps more than oil pump function. Check the cast iron shell is not cracked at snout.

I tightened up my oil pump, reducing the clearance on both sides, but it still wet sumps off the dip stick in about 3 days. I guess it's going through the gears.

Dave
69S

You need to take it apart and look at the fit of the Gear to body. Both the end play and the clearance on the diameter are important. When I say take it apart I mean all the way. I have done many pumps and have found a few that have had bits of metal run through them. Look for any grooving in the sides of the holes for the gears, a mark of any kind on the pressure angles of the gear teeth is a bad thing. Pumps with higher outputs all seem to have tighter fits cylindrically and gear teeth in good shape. I use pressure gages to keep an eye on the condition of the system. When the bike is full hot and idling don’t be surprised to see very low or nothing but on a hwy run you would like to see 40lbs at 4000 RPM. Use a gage with a 100lbs max read. Here are some pics:
http://tinyurl.com/2ahzb2p

The gears are only half of the seal point. The pump body can be scored and/or scratched as well. The pump's effectiveness depends on the condition of both the gears AND the body. If either is bad, neither will work well. Although the gear will wear, the body is much softer and will score. Oil is pulled and pushed by the gears through these arches. This is where the pump does its work. Nicked gears and scratched bodies will allow bypass to occur reducing the effectiveness of the pump and will allow oil to return to the crankcase while sitting. Bringing the sides in by reconditioning is good, but rarely fixes the issue in totality.

NorBsa,
thanks for the pics on pump over haul.
When I get to mine I now have a foggy idea what I'm in for.
Hobot that Avatar is sick :twisted:
That's not one of your friday nights out in the garage again? Or is it?
Marshal

1. most important oil pump factor is as Greg says, nothing busted up or scored too deep and the seal to case base and TS cover nipple. Wet sump is innate to the design brand new perfectly installed, just a bit longer to drain than a worn damaged pump but either can supply the meager oil flow needs into crank and to head.

2. Burning Commando was a photo a decade ago from a famous big twin biker event that got so out of hand burning things like buses that police shut it down.
It fits both my mood on Commandos and some reality of their fate in my hands.

3. For my off the wall Ms Peel I'll try to get one of DynoDave indexed pumps and get rid of the excess pump parts collection as I back out of restoring repairing Commandos forever and ever.

4. Hope to replace avatar with one of Peel and me air borne sideways in chicane, trailing flames and smoke off into blazing sunset...

Hobot not to jack the pump thread but where was that rally?
That is outta hand when folks start burnin up vehicles.
I've seen the Jap bike smash in the 70's by OMC at flat tracking events.
But that was about it.
At same events, I've heard stories of lads Jap bikes being kicked over off the side stands too.
That in my opinion is just wrong
Marshal

Thank you all for your responses - and especially Norbsa for the pics. I now feel reassured I was on the right track.

Paul.

norbsa48503 said:

You need to take it apart and look at the fit of the Gear to body. Both the end play and the clearance on the diameter are important. When I say take it apart I mean all the way. I have done many pumps and have found a few that have had bits of metal run through them. Look for any grooving in the sides of the holes for the gears, a mark of any kind on the pressure angles of the gear teeth is a bad thing. Pumps with higher outputs all seem to have tighter fits cylindrically and gear teeth in good shape. I use pressure gages to keep an eye on the condition of the system. When the bike is full hot and idling don’t be surprised to see very low or nothing but on a hwy run you would like to see 40lbs at 4000 RPM. Use a gage with a 100lbs max read. Here are some pics:
http://tinyurl.com/2ahzb2p

Click to expand...

Norbsa,
I need a little help understanding what I see in the photos. The photos show you have tighten up the gap between the teeth. I take it one of the goals of lapping is to reduce the clearance between the teeth. How was that accomplished by lapping the sides of the gears? My demented mind is suggesting the only way to reduce that gap would be to lap around the circumference of the gears, thus reducing the length of the teeth?
I know I missing something?
G

T95
You can't lap or fix a pump that has passed something and marked the gear teeth or the body bore. So you lap what you have, build it back up and check the pressure it makes. If it can't make 40lbs at 4000RPM with hot oil buy a new pump.

I know I have seen "modern" hi tech oil pumps being sold for Commando's. I assume they were for racing & over kill for the average guys bike but being more modern are the tight tolerances capable of preventing wet sumping? My bike wet dumps in days but according to my oil pressure gage has very good pressure. Anyone?

I have seen five that had machining that was so ruff on the back side that the gasket has marks on it were the oil was blowing by. I have also seen the sink washers so loose as to just let the oil by. Take it apart and fix it.

gtsun said:

I know I have seen "modern" hi tech oil pumps being sold for Commando's. I assume they were for racing & over kill for the average guys bike but being more modern are the tight tolerances capable of preventing wet sumping? My bike wet dumps in days but according to my oil pressure gage has very good pressure. Anyone?

Click to expand...

The srm one is no longer listed on their site. Maybe designing a better one?

It's obvious to me by the design of the oil tank that Norton knew/expected wet sumping as part of the engine design. The way the breather hose is routed to the tank so that oil accumulated in the sump can just pump from the breather into the tank makes that pretty clear. On an actual wet sump engine, the breather runs directly to the intake manifold or air cleaner box because there is no danger of the breather picking up raw oil and pumping it into the engine.

" I take it one of the goals of lapping is to reduce the clearance between the teeth. "

Lapping the pump is to eliminate excessive clearance between the ENDS of the gears and the cover plate. There is no lapping of the teeth of the gears so you can't really do anything about that when reconditioning a pump. The more clearance there is between the gear ends and cover plate, the faster the wet sumping will occur. Tight clearance (per the shop manual) will greatly reduce the speed of wet sumping but it will not eliminate. My 850 went from dropping several oz overnight to less than 1oz in two days after lapping the pump but it still wetsumps. I don't think there is any way to stop it within the design setup of the engine and again, from the way the oil tank/breather is designed, it is apparent to me that Norton knew that too.

T95 said:

I need a little help understanding what I see in the photos. The photos show you have tighten up the gap between the teeth. I take it one of the goals of lapping is to reduce the clearance between the teeth.

Click to expand...

The "pumped" oil is actually carried around the periphery of the chamber by the gear teeth, the pumped oil does not pass between the gear teeth where they mesh.


Lapping the pump is done to remove the side clearance that occurs from normal wear between each pair of pump gears and their respective chamber walls so lapping helps reduce the amount of oil which can bleed back around the sides of the gears as they rotate. The larger the clearance, the less efficient the pump becomes, as more and more oil leaks away around the sides of the gears back to where it started, instead of being pushed out of the pump, and the clearance increases the rate of "wetsumping"


Much of the blame for "wetsumping" is directed at the pump, however the oil can also wetsump through the OPRV (except for those engines fitted with a MkIII timing cover which do not recirculate their blown-off OPRV oil back to the pump). Oil can also escape from the oil pump gasket face or timing cover gasket face.

Information on how to correctly lap the pump is included in the workshop manual.

L.A.B. said:

The "pumped" oil is actually carried around the periphery of the chamber by the gear teeth, the pumped oil does not pass between the gear teeth where they mesh.

Lapping the pump is done to remove the side clearance that occurs from normal wear between each pair of pump gears and their respective chamber walls so lapping helps reduce the amount of oil which can bleed back around the sides of the gears as they rotate. "

Click to expand...

MexicoMike said:

"

I take it one of the goals of lapping is to reduce the clearance between the teeth. "

Lapping the pump is to eliminate excessive clearance between the ENDS of the gears and the cover plate. There is no lapping of the teeth of the gears so you can't really do anything about that when reconditioning a pump.

Click to expand...

Mexicomike/L.A.B,
Thanks for the clarification, it makes perfect sense now. I took a look at norbsa photos and compared the before photo 19 and after photo 22. I thought the lapping had reduced the clearance between the teeth. Now I see the teeth have just rotated slightly which appears to show a reduction in clearance between the teeth.