1972 combat oil pump question.

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First of all, the bike runs good, there is good oil return to the tank. I have no way of monitoring the pressure, apparently Norton didn't think it was critical. I wasn't too concerned, until I had the inside primary off to rebuild the gearbox. I was waiting on parts, went out of town for about 10 days, only to come home and find about half the oil drained out of the tank, through the low bolt hole in the crankcase. Anyway, I finished the gearbox, got the bike back on the road, it still runs fine, and the gearbox shifts good, and is nice and quiet.

Now I am paying much closer attention to the oil. It doesn't have to sit too long (over night) before enough oil goes into the crankcase, then gets puked back to the oil tank through the vent pipe, when I start it. (I'm fairly certain this doesn't have a cam driven vent). My BSA buddies have antisump ball/check valves on those inferior machines, I know there are many options I can do with antisump valves, but I want to be assured the oil pump is working right.

Is it worth re-building the pump, or is it better to replace it? Should I devise a way to check the oil PSI?
 

marshg246

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You can improve the oil pump clearances and slow the problem. I wouldn't be shocked to see a new pump not a great deal better. If the gears are not worn, dressing the four surfaces to have no clearance but not binding will stop a lot of the problem. With new gears, oil can still get through. With worn gears nothing much helps.

I always install the madass140 oil pressure switch - if the light goes off and stays off after I start the bike and oil is returning to the tank, I'm happy. Oil pressure gauges are nice but tend to worry people.
 

rvich

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Here, watch this if you wanna have some fun!

I have a manual valve in my line that I turn off when I'm not riding my bike.

PS - yes it's normal!
 
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Thanks for the replies. I wired the the bike, and used the charge light for a future oil PSI switch. I'll check out the madass psi switch. Matt with cNw sent me a link for some "in line" valves that have an ignition interlock switch. I'll probably just install the oil psi switch and the in-line valve for now. This is a much better bike than what I'm use to buying (usually in boxes), so my approach has been different. Re-wire and electric start first, carburetors, then the gear box was next, this winter I'm going to work on the isolastic, so I'll be back. Thanks again for the replies.
 

rvich

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Just FYI, these valves (any of them) are highly controversial here. I'm surprised the conversation hasn't gotten a rise. The worry is of course that you will starve the engine for oil. It's not an unfounded fear. Do your research before going in this direction. It could be argued, successfully I think, that it is a fix for a problem that doesn't exist. If you have the breather off the back of the crankcase, your bike is a good candidate for the reed valve there like the ones sold by CNW as they evacuate the oil well after a wet sump and solve some other issues with crankcase pressure. Do a search for "reed valve" for days of reading material. Another search would be "crankcase breather".
 
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First, there are many things to look out for and eliminate before going to the next level, take timing cover off and remove oil pump and check with a straight edge the flat part of the oil pump. If OK fit it back using new gasket and rubber cone.
Take off oil feed pipe and temporary block inlet pipe and fill oil tank to normal level to see if oil is coming back through a broken return pipe. If oil is coming out, the metal pipe inside the oil tank is broken.
If that's OK, check timing cover ball valve is working. If all OK , refit timing cover and feed pipe and consider other options.
 

L.A.B.

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Take off oil feed pipe and temporary block inlet pipe and fill oil tank to normal level to see if oil is coming back through a broken return pipe. If oil is coming out, the metal pipe inside the oil tank is broken.

A '72 oil tank doesn't have an internal return pipe.

If that's OK, check timing cover ball valve is working.

A '72 wouldn't normally have a ball valve in the timing cover.
 
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Well LAB are you telling me that the Commando doesn't have a pipe with a small hole near the top where the oil returns to the oil tank?
Well I never knew that.
 
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Strange....several crossed wires? (poor written english ?)
ball check valve=aftermarket conversion...yes- not factory normal
Yes all roadster oil tanks return path crosses the rear oil tank skin to become internal , and up next to the filler cap.
Am I missing something?
 
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If you want an internal check valve this is the solution. It really works. I've had it done on all 3 of my riders and the one I'm currently building. With that said even with the mod it loses a bit in to the sump if you let it sit for several weeks but not to the point you can't start the bike safely and wait for the return pump to clear it. The return side of the pump is higher volume than the supply side. If you let it sit for six months even with the mod you may need to drain the sump. Well worth it to me as my bikes would completely drain the tank in just a few days. It's completely safe as the full pressure of the pump lifts the check ball. No valves to worry about turning on or losing prime.
 
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I should add on the one I had the oprv drilling done, it does much better. Would highly recommend you have all the mods done if you go this route.
 

L.A.B.

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Well LAB are you telling me that the Commando doesn't have a pipe with a small hole near the top where the oil returns to the oil tank?
Well I never knew that.

No, that's not what I meant. What I meant was that the return pipe does not rise through the contents of the oil tank as the section of pipe is external, therefore the contents of the oil tank won't "drain through a broken pipe" as you suggested.



Edit: Example of what I would consider to be an internal return.


Strange....several crossed wires? (poor written english ?)
ball check valve=aftermarket conversion...yes- not factory normal
Yes all roadster oil tanks return path crosses the rear oil tank skin to become internal , and up next to the filler cap.
Am I missing something?

I thought what I meant would be fairly obvious (see above) but perhaps not.
 
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baz

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First, there are many things to look out for and eliminate before going to the next level, take timing cover off and remove oil pump and check with a straight edge the flat part of the oil pump. If OK fit it back using new gasket and rubber cone.
Take off oil feed pipe and temporary block inlet pipe and fill oil tank to normal level to see if oil is coming back through a broken return pipe. If oil is coming out, the metal pipe inside the oil tank is broken.
If that's OK, check timing cover ball valve is working. If all OK , refit timing cover and feed pipe and consider other options.
What timing cover ball valve?
 

baz

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Unless the timing cover has the 'AMR' check valve conversion then there wouldn't be one.
Yep I'm aware of the AMR mod ,it's been described on here before with various degrees of success reported
But there's nothing in the original post to indicate this had been done?
Very odd that!
 
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I'm one of the people who consider it a non-problem, invented after someone decided this unavoidable product of the design had to be corrected. Nobody ever heard of "wetsumping" until 20+ years after these bikes were produced. :rolleyes:

The only thing I would (did) do is to pull the pump/true the surfaces as per Norton's service manual guidelines. To me, that's a good idea anyway to ensure the pump is in the best condition possible, and it reduced wetsumping dramatically on my Commando - from 2 0z overnight to 2 0z in 4-5 days. The breather, as noted, is a good thing also, but beyond that - forget about it! ;)
 

L.A.B.

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Yep I'm aware of the AMR mod ,it's been described on here before with various degrees of success reported
But there's nothing in the original post to indicate this had been done?
Very odd that!

Just Bernhard getting his wires crossed I think?
 
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I'm one of the people who consider it a non-problem, invented after someone decided this unavoidable product of the design had to be corrected. Nobody ever heard of "wetsumping" until 20+ years after these bikes were produced. :rolleyes:

Maybe it was not called "wetsumping", but it was well known both for manufacturers and riders, even before the Commando. Norton did advice it's customers to return the oil pump for servicing if excessive. BSA included two valves, one after the supply pump and one in the pipe sucking oil from the sump. This valve stopped oil return line (and external oil filter on some models) draining back to the sump. Velocette fitted an automatic valve in the feed pipe.
The problem became more noticeable with the introduction of multigrade oils.
 
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baz

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Maybe it was not called "wetsumping", but it was well known both for manufacturers and riders, even before the Commando. Norton did advice it's customers to return the oil pump for servicing if excessive. BSA included two valves, one after the supply pump and one in the pipe sucking oil from the sump. This valve stopped oil return line (and external oil filter on some models) draining back to the sump. Velocette fitted an automatic valve in the feed pipe.
The problem became more noticeable with the introduction of multigrade oils.
The term "wetsumping" is a little misused these days as wetsumping used to refer to proper wet sumping IE whilst the engine was running the scavenge side of the oil pump couldn't keep up
 
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