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gunner Offline OP
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I'm looking to get my 1972 Combat Commando timing side cover converted to Mk3 spec with the anti drain valve.

Does anyone know if there is a UK supplier still performing this work, I can't seem to find anything on the web.

Alternately, how difficult is this conversion for a local specialized engineer, assuming I can find someone competent enough.

I can see that the conversion would involve machining the timing cover so that the piston and spring can be added but are there any other considerations? Is there an O ring or oil seal fitted to ensure oil doesn't leak past or does the conversion simply rely on a close fit between the piston and cover? Also what about spring pressure, does the cover need to be machined any deeper or shims added?

All info welcome !


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1967 B44 Shooting Star
1972 Norton Commando
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The MKIII timing cover has a bulge in its outer face to accommodate the plunger and its spring ... they need somewhere to retract when oil pressure pushes the plunger away from the seal on the oil pump outlet.

I suppose you could accomplish something similar by welding a bung onto the timing cover, and then machining it to take a standard MKIII plunger and spring,

The MKIII system is not foolproof however, I've had 3, and have found that the plunger tens to stick in its open position ... at least it fails safe.
.. Gregg


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There is NO conversion to MKIII style. The conversion is to Nortech. spring with ball bearing not piston like MK3.
The MK3 covers are actually inferior as the piston's tight clearance very often jams due to a tiny bit of grit.
The early 90's drawing(sketch) is on my website.
I installed it on my friends combat. It also had the pump o-ring job done.
I agree the nortech mod is way better than the MK3 cover, and way better(safer) than ANY inline wet sump valve.


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This is what you are after.

http://www.amr-of-tucson.com/anti-wet-sump-information/

Note: It's Nortec, not Nortech.

Originally Posted by Dave Comeau
.
I agree the nortech mod is way better than the MK3 cover


Jon W.


1957 6T Thunderbird 650
1968 T100R Daytona 500
1971 TR6R Tiger 650
1970 BSA A65F 650
1955 Tiger 100 - Project
1971 BSA A65 650 - Project
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gunner Offline OP
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Thanks for all the info, I didn't realize the conversion was to Nortec style using a ball and spring.

As part of the conversion AMR modify the pump by adding seals so looks to be a good modification, additionally the OPRV can be changed to dump excess oil into the sump.

If I can't find anyone in the UK to do the conversion then I might get AMR to do the work but international postage is going to add to the price.


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I have done all 3 elements of the AMR mods. The mod for the OPRV drain to sump is a DIY job, as long as you have access to someone with a small vertical mill then other 2 of the 3 mods are simple and easy operations, the setup will take longer than the machining. I have the dimensions if you need them to give to a local machine shop, the 3 holes that need modifying are all existing holes so just need indicating off.

Timing cover, drill at 30 degrees to hit the OPRV in the gap between the threaded OD.



[Linked Image from i.postimg.cc]


Open out the pump shaft holes to take X ring

[Linked Image from i.postimg.cc]

Last op is to deepen the current hole in the timing cover that takes the oil from the pump so a ball bearing and spring will be pushed out of the oilway when the pump is pumping. No pics but on any timing case with the points cover the timing case can be clamped to a mill bed on the outer flange, as its a light cut the cover will not be bent by the cutting forces.

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Sorry of not knowing current Nortec name. However the drawing/sketch was taken from a nortec mod before AMR took over the process.
I'm not sure the mod I documented had the OPV leakage mod in the early 90's. Today it reverts the OPV operating mode FROM recirculate in the oil pump feed side TO timing chest dump mode like pre Commando and MKIII.


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gunner Offline OP
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Thanks for all the useful info and photos, that's really good to have and I can probably approach a local engineer with the detaila to do the work.

A couple of questions if I may:-
- what size ball is used, presumably it would need to be seat against the pump output spigot.I just had a quick look and I think 1/4 inch ball may work or something slightly larger. I've often wondered whether a nitrile rubber ball would seal better in the and other classic bikes, anyone tried it?
- What about the spring, could I use something like an A65 anti drain spring assuming the depth in the housing is similar.
- presumably the rubber cone around the pump spigot is retained to ensure the timing cover seals against the pump.


I'm a bit wary of modifying the pump as I've just bought a new AN pump. Their instructions say do not disassemble as its been selectively assembled and tested. I can see there's an oil seal on the input shaft but not sure about the internals.


Kommando PM sent.

Last edited by gunner; 02/22/21 6:33 pm.

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A new pump should reduce the original 4 leakage paths. I would not touch it untill you feel there is a problem.
My favorite is my combat and I have not had wet sump problems until after the "blow-up", which took out the original pump. Now that I have devised a revised combat pick up scheme it could not blow up again from a cam bush tab.
1/4 ball and a proper seat on the output nozzle is the solution. Mainly the spring should seat the ball. Exact pressure is not that important as the pump WILL unseat it if the pump is any good! A bigger ball will cause an unnecessary restriction in the outlet passage.


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I use Unit single non return springs, 1/4" ball.

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Oil pump

The X ring is size 012 in buna shore 70, you need an 1/2" end mill and create a Concentric hole over the 2 shaft holes 0.090 deep. The X ring is .070" cross section, its compressed by both the shaft and OD of the slot so the extra 0.020" depth of the slot takes the side expansion of the X ring.

O ring for the pump outlet the cover seals onto is 1/8" X section, 1/4" ID, 1/2" OD. This replaces the old conical rubber seal.

[Linked Image from i.postimg.cc]

Cover

Take the 5/16 hole the oil pump forces oil into down to the depth of 0.550", check before taking this step that this will not breech the timing cover outer surface. Norton added a bulge here for the MK3 as there is little extra depth to play with. Use an 5/16 or 8mm end mill as you want the bottom of the hole to be flat for the spring.

1/4" ball

The spring I use is the BSA Unit single one, BSA unit single ball check valve spring.

0.6" long 0.25" diameter and wire thickness is 0.015"

Part numbers 40-0381 or 40-0381 or 70-8124 whichever works

Add a 6mm hole at 30 degrees for the OPRV bleed off so the oil goes straight to sump.

[Linked Image from i.postimg.cc]

Crankcase

Also block the crankcase hole the oil dribbles from when you take the timing cover off, its already threaded 1/4" UNC so use a short grub screw, do not screw it in too far, just below the gasket surface.

[Linked Image from i.postimg.cc]

Not my pic but forgot who's it is to credit them.

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gunner Offline OP
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Thanks very much for the info, looks like a relatively straightforward job and hopefully will fix my Commando wet sumping issues.


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Originally Posted by gunner
I'm a bit wary of modifying the pump as I've just bought a new AN pump.
.

If you are STARTING with a new AN pump, you shouldn't have any wet sumping problems at all ???

I started my Commando ownership with a low miles 850 Mk 1 ( a bit beaten up though).
With the end plates in the oil pump flatted down, as per the factory workshop Manual,
it barely wet sumped at all. Ridden at least once a week, it never showed any signs of problems.

Its when they stand for months and months that folks start seeing these things.
And start worrying too much ....?

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gunner Offline OP
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Quote
If you are STARTING with a new AN pump, you shouldn't have any wet sumping problems at all ???

I agree with your thoughts and the possibility of adding oil seals to the pump only became apparent when the I became aware of the Nortec conversion and AMR website. Since my AN pump is new and already has at least one seal already fitted as standard I'm not anticipating any major leakage, so I'm more than happy to leave it alone.

The other mods are more of a belt and braces approach to ensure that if any oil does seep past the pump there is another line of defense against the sump filling.


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Originally Posted by gunner
there is another line of defense against the sump filling.

True.
But riding it, often, was a sure fire cure for this back in the days when these bikes were new ...
And it worked !!

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Quote
But riding it, often, was a sure fire cure for this back in the days when these bikes were new ...
And it worked !!

Again completely agree, however working 40 hours a week, keeping my 10 year old daughter and partner entertained, plus maintaining the other 2 bikes restricts my riding time on the Norton. Then there's the British weather which from November to March is either freezing cold, pouring with rain, snowing or a combination of all 3.

I think my resolution for 2021 should be to get out more on the Norton and A65 and B44 smile


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How about just starting the bike once a week and letting it run a few minutes to get the oil circulating?

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Originally Posted by 50-C11
How about just starting the bike once a week and letting it run a few minutes to get the oil circulating?

Most of the engine wear takes place on start up.

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Not a good idea to start up an engine and let it run a few minutes. Corrosive condensation forms inside, especially during colder weather. The oil temp needs to get above 180f to vaporize the condensation. If you are going to start it you need to ride it 10 to 20 miles to get the engine completely up to operating temps. Otherwise better to not start it at all.

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If there really is a sumpfull after a long standstill, just draining it into a clean container and tipping
back into the oil tank is only a few minutes work. If you have the wrench and a clean container to hand ...


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