Oil pump refurbishment

Put it back on the engine and lock the engine in gear with brake on?.

I've used aluminium soft-jaws successfully in the past. The gear is very hard.

That said, the current Andover pumps are a vast improvement on those supplied during the 1970s. All things being equal, I'd fit a new genuine one rather than flat the side plates on an original.

is it left hand thread

I agree with Richard Payne.

I bought a new pump from Andover Norton. At first glance it might seem a bit expensive, but it comes with a note saying that it has been selectively assembled by hand, and is pre primed.

Since putting it on wet sumping has completely stopped. The tank level does not drop at all over a period of weeks.

Worth the money by my reckoning.

The shaft & gears are all super tough and will put up with a lot of bashing or vice work.

I am presuming the pump has been removed from the engine. Screw the pump down onto a wooden surface. ie work bench or Workmate so that the driven gear is overhanging an edge. This will then give you room to heat the nut until it is just about to change colour. Then hold the driven gear using the likes of a pair of mole grips or pipe wrench while attacking the nut with a ring spanner.

The nut has a standard right hand thread, so turn the spanner anti-clockwise to undo. The 6 start worm gear has a left-hand thread.

The new A/N pumps are very well made but expensive.

Neil,

before you further go ask yourself do you need this nut removed. simply undo the four screws( you don't need to remove them if they foul the drive gear) to release the end plate to dismantle pump, to take up end float you will be removing some material from centre section anywayso no need to work on drive end = the gears will match any scoring they have created.

As return capacity of pump is much greater than feed you only need concentrate on end float for gears at end with brass plate.

the hard part is rubbing the right amount off to take up float, it's trial and error repeatedly assembling pump to check how freely it turns

The orginal Dominator pump was designed with a life span of around 100,000 miles. The 6 start worm added in the early 1960s to double its speed, has the unfortunate consequence of seriously reducing this life span. The use of cartridge filtering does help by removing a significant amount of rubbish, from the system but only does so after the junk has passed through the return side of the oil pump. This often leads to chipped gear teeth and scoring of the chamber sides and ends.

This can not be ignored otherwise the scavenging process is impaired, often leading to smoky start-ups and discharge from the breather.

The Commando oil feed system has an anomally not found in the pre-Mercury Dominators. This being a proportion of the feed being recirculated straight to the return side of the pump. Add in the pressure rocker feed and the amount of oil heading to the big ends can become marginal, especially when the oil gets hot. Many owners fitting pressure gauges to their Commandos had watched 50psi drop to just 10psi on long fast journeys.

It really does pay to completely dismantle the oil pump, then check and service the various components as much as possible in order to get it to an A1 condtition.

Attached photos show dismantled pump. While the inner chamber faces looked good, the end plates were scored and chamber return sides well hacked by debris. If you look carefully, you can also make out the dents in the gear teeth.

When I tested the oil pressure on my '55 Dominator, there was 0-5psi when hot. Time for some attention. Well, it had been wet-sumping, so that meant pressure gears wanted attention in the oil pump.

To lap the oil pump, it is not necessary to dismantle the oil pump completely. I wasn't able to remove the drive gear, so gave up, and lapped the pressure side of the pump, and the cover plate. When the plate was completely flat, and the gears level with the housing, I did a trial assembly. It's right when there is light friction when you turn the drive gear. Fortunately, my pump was otherwise in good condition. When it went back on, more like 5psi. At least it's something....

Hi Neil

I removed my gear using the round toothed section of an adjustable parrot wrench, heavily wrapped in electrical tape.

Put it on the floor and push down as you push the spanner to undo the nut and then all your weight is both pushing on the spanner and onto the lever keeping the jaws closed.

I took Richard Paynes advice and put a new Andover Norton pump onto my commando. Fitted like a glove and all but cured my previously very bad wet sumping problem. I can now leave the bike for a month and still have oil on the dipstick.

My old pump sold on eBay for nearly £50, making the decision to go new even better!

Hi Steve.

At the risk of going off topic here I am looking to change the oil pump on my Mk111 for an Andover Norton one. The job looks straight forward enough but wondered if there are any unforeseen pitfulls I should be aware off before I going ham fisting in.

Mark.

Previously mark_chapman2 wrote:

Hi Steve.

At the risk of going off topic here I am looking to change the oil pump on my Mk111 for an Andover Norton one. The job looks straight forward enough but wondered if there are any unforeseen pitfulls I should be aware off before I going ham fisting in.

Mark.

Make sure you install the gasket the correct way or it blocks some of the holes. A spot of thread lock on the nut is a good idea as there is no room for spring washer or locking nut.

It's definitely a good idea to have a copy of the factory manual.

The correct adapter to enable the points oil seal to pass over the cam is a help - although it can be done with tape.

The Mk3 has an anti-drain valve plunger built into the timing cover opposite the pump outlet. It is likey to be stuck open - don't think it's missing and try to fit another ! It can usually be freed by warming the cover and banging it on a block of wood. I find it worthwhile to polish the plunger so that it is a slightly easier fit in the bore and will return more easily.

With the combination of a new pump and a freely moving plunger, you should have an oil system that retains the oil in the tank over a considerable period.

Previously karl_nixon wrote:

Previously mark_chapman2 wrote:

Hi Steve.

At the risk of going off topic here I am looking to change the oil pump on my Mk111 for an Andover Norton one. The job looks straight forward enough but wondered if there are any unforeseen pitfulls I should be aware off before I going ham fisting in.

Mark.

Make sure you install the gasket the correct way or it blocks some of the holes. A spot of thread lock on the nut is a good idea as there is no room for spring washer or locking nut.

Thank you. Advise greatly received.

Mark.

Previously richard_payne wrote:

It's definitely a good idea to have a copy of the factory manual.

The correct adapter to enable the points oil seal to pass over the cam is a help - although it can be done with tape.

The Mk3 has an anti-drain valve plunger built into the timing cover opposite the pump outlet. It is likey to be stuck open - don't think it's missing and try to fit another ! It can usually be freed by warming the cover and banging it on a block of wood. I find it worthwhile to polish the plunger so that it is a slightly easier fit in the bore and will return more easily.

With the combination of a new pump and a freely moving plunger, you should have an oil system that retains the oil in the tank over a considerable period.

Thank you Richard. I have a Norton Triumph workshop manual. Its not very detailed and does not specifically detail the changing of an oil pump. But I am sure the job is straight forward enough especially with the helpfuladvise given.

Mark.

Neil,

It is not a tricky job, but I agree with Richard (again!) -it is worth having a read of the manual.

Have a look at Britmoto.com.

Also, it is worth changing both lip seals and the having the tool for getting the lip seal over the timing shaft is a boon. I got mine from Andover Norton, but I think NOC also has it.

cheers

Steve

Neil............Definitely a good move to add some oil proof sealant to all of respective the mating faces. Unless you have taken the time to surface grind each face to a 1200 grit finish they will let hot oil pass between them. You would not put any other parts of the engine back together without a gasket or goo to help seal repective faces. Crankcase halves being an obvious example.

The original Commando pumps were very poorly made. The demand for them was so high that corners were cut during production to churn out high numbers while saving money. It is not uncommon to find pumps with such bad finishing that you can actually sharpen finger nails across the supposedly finely ground faces.