High capacity oil pump

Why do you wish to make this mod'?        What benefits are you hoping to achieve?                                                   The pump will easily replace the earlier pump, but it is normally driven with a 6 start spiral gear on the crankshaft.            This would also necessitate having a 6 start gear on the pump.                                The later engines fitted with these pumps also had the benefit of larger oilway  drillings. Further to this, the rocker shafts would ideally need to be changed from scrolled, which you have at the moment to plain shafts. These shafts have no spiral oil groove, just an oil hole and a flat on one side The extra capacity of the pump could give you the oppertunity to create a positive oil feed to the rockers. However this will open a whole can of worms as the early engines don't  have the necessary  drainage to get rid of the extra oil. It might be an idea to continue to drive the pump with the existing 3 start gears or you could get an excess of oil pressure, which,  despite what some people might think, is not beneficial. You may also be told that you will need new con rods that have a miniscule oil spray hole on one side above the big end eye. You dont!         This modification if you go all the way is not going to be without considerable expense.

I fitted a set of 6start gears to a std  99 pump and the extra oil spraying round the timing case drowned my  distributor  and gave me oily plugs .  They are going rusty hanging on a nail now.

I re-furbed my pump and  although much improved it still wet sumps 1/2 a tank if left for a few weeks ,but then it did that back in the day.  A new uprated pump fitted with your 3 start gears would probably work  OK.  I have read that some new pumps are not best quality, best ask around. Where are you based?. Help may be near.

To refurb a pump you need emery paper and a flat surface, a piece of plate glass is perfect. You also need an hour of time and patience to stop, test and clean a lot to ensure you do not go to far. I have done many pumps over the years.

If you decide to go ahead and buy the new pump, then change the drive gear back. Unless I'm mistaken - the 'high-capacity' pump is no such thing. The original pump had a 3-start worm on the crank, and a gear on the pump to match. The 'High Capacity' pump is simply the same pump, but using a 6-start worm & gear set - so it spins twice as fast, and delivers twice as much oil! If your engine is not prepped for it, then expect trouble - flooded cylinder head, for one.

If you are buying from Norvil - then check out their website. I think they offer Tech Advice over the phone on certain days, At least, they used to.

Hi Andy,  no the pumps are not the same. The uprated pump has delivery and scavenge gears which are about half as large again as the original pump.

There are quite a few myths floating around about oil Dominator pumps that some people just want to believe. The consequence being they waste money on unnecessary upgrades and sometimes causes more damage than fix a problem.  Adding a 6 speed gear/worm set to an 88 or 99 oil pump is one of these. This is a total waste of time as all it will achieve is to pump excess oil via the pressure release valve into the timing cover where it will try and escape via the Magneto or Distributor or the right side exhaust pipe.

Unless it is totally worn out there is no need to change the oil pump on an 88 or 99 unless you decide to fit pressure fed rockers. Even then just upgrading to a higher capicty pump will suffice.

If your bike is wet-sumping then service or change the pump.  In the RH Archives issue 327 has an article on how to service an oil pump.

I was talking to a well known London dealer, about oil pumps, and he told me the following. A Norton rep came into the shop on day, and he told my dealer friend that when they went over to the six start oil pump gears, then oil leaks got worse. I changed the oil pump gears on my 1960 99, but I added all the later upgrades. The oil holes in the con-rods, larger crankcase oil feed holes, plain rocker spindles, larger oil junction block, and the pressure feed to the rocker arms. The oil control piston rings will have to be changed from the earlier so called Hepolite super drain ones to the Twiflex, or the later and better post 1966 oil control rings. I did it at the time, as the work was completed for me by the late great Jimmy Boughn the ex AMC development, and race engineer. My 1963 has the three start oil pump and the earlier designed oiling system, and I have not had any oil problems. If it an't broke do not try to fix it. The Commando had oil problems with changes to the oil pump gears and the piston rings.

Hello Jason,  I have a friend nearby who would be happy to refurb your pump for you ,he is more than capable of doing this and has done work previously for other members, as a member of the   club there would be no charge. We are in Reading, Berkshire and you could post / courier the pump if happy to do so.

Hello Phillip, you say that a standard pump fitted with 6 start gears would cause an excess of oil to enter the timing case . With the consequent problem of the mag'/distributor becoming contaminated ,  Do you know this to be factual or is it conjecture?         I think it likely that a standard pump on 6 start gears would probably pump less rather than more, I haven't run that test yet so can't  be certain.                       If there were to be excess oil in the timing chest would it not drain back to the sump via the holes in the back of the timing chest .                             Further to that, why would the oil specifically target the right hand exhaust pipe?

Jason, some of the posters here have been working on twins for decades and have  extensive experience with this issue. and are happy to lead you.,  If you accept what they advise you will save  much frustration and cash.

Ian - the gear wheel has something like 24 teeth.  A one start worm would drive the pump at 1/24 of the driven worm speed.  A three start worm drives at 1/8, and 6 start at 1/4.  So the six start worm delivers twice as much oil if the pump design is not changed.  And as those far more experienced than me have said above - twice as much oil creates its own issues.

David , I guess you better tell the guy who quoted Wikipedia. However I note that the post appears now to have been removed. I'm  not entirely sure of your maths but driving a pump at twice it's intended speed won't  necessarily  deliver double the ammount of oil , you can exceed the capacity of the pump and efficiency can be reduced. ( talk to Ashley) The only oil problems  are those caused by inefficient drainage from the cylinder head

There is nothing wrong with the 3 start oil pump, if anything it is most probably easily capable of keeping an 850 engine well lubricated. The clue is in the title capacity, not pressure. Not one person on this planet has given me the actual reason why Norton went to six start - capacity or pressure. 

Both pumps can supply adequate pressure, if both were opened ended and driven the the same speed the 6 start will deliver twice the volume of oil. Once restrictions come into play in the systems then as Ian says, you will not get twice the flow as the systems are different, one will see more restriction than the other. The idea that if you fit a pump with twice the capacity and use a similar system pressure, it will deliver twice the oil to the system is flawed. As above the 6 start exceeds the capacity of the 3 start, but is it anymore efficient, not really considering the engine design. 

Considering that both pumps can supply adequate pressure, then just why was a 6 start pump needed. Oil has two main functions, lubrication - we have pressure so not a problem, so it must have been for removing heat.

Considering the holes in the conrods, the holes are uncovered for a short time period so would not affect a 3 start pump that much. The increase in journal diameter creates a larger leakage path out of the journal, could this have been the reason for the change but unlikely. The feed to the bearing shell and how the oil film functions is complex, and not solely related to system pressure, but again easily satisfied by the 3 start pump, just look at modern engines and the oil pressure they use. 

So to use a 6 start pump and not use it to its designed capacity was a negative step, no matter what size the oil ways, unless the point of delivery hole diameter follows makes no difference, where oilways would count is the return side from sump to crank which is not fully utilised. I will leave this for an article that is going to be in the Roadholder, it will be a good read, and thanks for those putting it together. 

The official line was that the bigger crank journals needed it. It was also known that at high revs the pressure could drop to almost nil.Centrifugal action sucking the oil away as fast as it was supplied .Perhaps this was a worry.that  cavitation might be a problem  for the shell bearings. 

The answers to most of Ian's questions can be found in the Technical section of this Forum and in the postings in both this thread and others connected to the Norton twin oil delivery system. In my selection of John Hudsons notes/letters he refers to the need to change to the 'S' type of pump and backs this up with figures obtained from the developmental department where he worked.

Basically these state that the 3 start  'standard pump delivered about 12 gph at 6500 rpm at 90*C of which 11.5 gph went through the crankshaft. 

The larger journals of the 650 engines needed the larger capacity 'S' oil pump to maintain more than 12 gph to the crankshaft but, when pressure fed rockers and con rod bleeds holes were added to the system the pump could not deliver, especially at lower revs.

Fitting a 6 start worm/gear drive to the 'S' pump produced figures of 25.5 gph at 6500 at 90*C of which nearly 13 gph went through the crankshaft and  a staggering 12 gph through the relief valve. So next to nothing was being lost via the rocker spindles. Possibly because they were all plain with just a tiny timed feed hole to the rocker ball ends.

The above figure can also be found in the original Dominator Service Notes which were written by John Hudson, Al Osborn, Colin Newman A Non plus the odd scribble from Tim Stevens and some other bloke who clearly does not know what he going on about.

A few photos attached of badly manufactured pumps. Generally from Woolwich.

From Phills post it would seem that a later pump with 3 start gears would be a fair bet on a otherwise std 99.     Perhaps supplying enough oil to  uprate  the LP  head supply  with a simple change to the tank union.  Somewhere between the std  bore and the Jubilee.Just looked in my valve chambers doing tappets (2 thou change on one exhaust in 20 years)  and the exh side still looks a bit underlubed ,  How to bias the flow a bit to that side? Something to sleep on.

Definitely not worth the bother unless the old one has badly worn teeth.  When I used to overhaul Jaguar engines I had small 6" square pieces of plate glass cut and used grinding paste to grind tappet shims for the overhead cam followers.  Better than emery cloth, although you would be best to use 1000 grade or finer wet & dry than emery.  Face down the grooves in the bronze (or is it brass?) body plate - or just turn it over with the smooth side inside.  You can't do anything about wear on the gear teeth but if necessary you can also face down the sides of the gears if they were too tight.  I also used to use this method for the Jaguar XK engine's oil pump - which is a touch larger than the Norton's (!!) and has concentric rotor gears, but the correct clearances could be achieved and checked with feeler gauges. 

Andy  Dunn says this about the pumps:-

"The pump body is the part that should be ground down

Rubbing down the pump body is the only sustainable way to go. Rubbing down the end plate:- (1) does nothing about wear in the body (2) eventually leaves nothing for the screws to thread into"

Whilst I would agree with part (2), I think you are only likely to do this once on a normal classic touring bike (as opposed to "racing") but I would disagree with point (1).  It's no good just facing down the body if the gears are running in grooves in the plate.  If you're worried about the plate's thickness relative to the threads, then perhaps a bit of both would work?  You would need to judge how much metal would need to be removed from the plate and how much thread length would remain.  I imagine that these simple plates would be easy to make so I would expect some to be available new.  Has anyone seen any? 

Any wear made by the gears at the back of the body would still remain in any case.  Facing off  the body would need to be done very carefully if the gears had indeed worn a recess in the back of the body as you would allow the end plate to push the gears further to the back so they might catch on a worn lip.  Do a little at a time with this method, keeping a precise check with a micrometer or calliper gauge to make sure you are grinding metal off evenly.  Assemble the pump from time to time to make sure it moves freely.

I have memories of making up a shouldered pin punch  possibly to remove the nipple and using a small puller to get the gear off.   I think an internal  gear can be fitted the wrong way round too ,so look closely . All in all not a difficult job as long as nothing too aggressive has been thro the pump.

Nice figures from Phil, can anyone spot the problem? I suspect it is where it all started to go very wrong. The idea worked as Phil indicates in his post for the 650, however the oil feed to the head with the analysis above leaves one big problem - heat, at the time of JH figures, not a problem as the previous method coped well enough to cool the head and considered OK to continue with. Now consider the 750 & 850 used with improved fuel. 

Not only do the parts in the head need lubrication, the heat needs to be removed. The race shop in 1963 knew this, and actually had the solution - evidence exists, but strangely it never made it to the production bikes. I will not steel someone else's thunder on that one. 

0.5Gph to the head, Hmm!!!.