Poor circulation in Domi 99

It all depends... On SAE 50 left overnight in -5 degrees the oil presure on start will exceed 100psi. That's from experience. However, in normal conditions in summer on a hot day on a long ride it can sit just above zero. What pressures are you reading and under what conditions? Is your oil circulating OK? Is the bike showing any signs of under lubrication? It could be that there's nothing amiss. Gordon.

AS Gordon has rightly pointed out there can be lots of reasons for both apparent and actual low oil pressure.

On a cold start-up the oil pressure in a Dommie twin is usually so high it triggers the relief valve in the timing cover. This is no bad thing as it means some oil for thetiming sidechains and bearings immediately.

After a few minutes of warming up the oil pressure should be around 45 to 55psi. This drops down to around 20psi once the engine is being used in ernest but type of oil pump, pump gearing, rocker feed type and many other factors can change this.

If a change of oil pump or gearing does not appear to improve the pressure.......where is it being measured from? Then I might be inclined to suspect worn big ends, worn oil seals or other oil feed issue.

Some people make the mistake of thinking that the return flow to the oil tank should be continuous....on these dry sump engines it isn't.

The pressure relief valve is often overlooked on rebuilds and needs to be checked. It's purpose is to regulate maximum oil pressure and is adjusted by shimming. Should open at between 50-60lb/sqin I think, so you should see a steady increase from approx 15lb/sqin min. at tickover to max (50-60lb/sqin) as the revs rise above 2500rpm hot or cold. High oil viscosity will only increase tickover pressure when cold.

I would be very surprised to see 50-60 psi on a warm 99 with a single start oil pump worm. Just doesn't happen in my experience. Certainly worth checking the pressure relief valve in any case. A big end siezure is odd though. With lubrication failure you would normally (but not invariably) expect the pistons to nip up first. I take it the sludge trap wasn't blocked when you stripped it.

Previously Gordon Johnston wrote:

I would be very surprised to see 50-60 psi on a warm 99 with a single start oil pump worm. Just doesn't happen in my experience. Certainly worth checking the pressure relief valve in any case. A big end siezure is odd though. With lubrication failure you would normally (but not invariably) expect the pistons to nip up first. I take it the sludge trap wasn't blocked when you stripped it.

Indeed pressure can be very low on a hot engine, I've heard it said on more than one occasion that the big ends get more oil from centrifugal forces from the sludge trap than they do from the pump, however, big ends nipping up isn't that uncommon if you have a lubrication failiure that restricts the oil circulation, this is exactly what happened to the Commando refered to in the 'Persistant wet sumping' thread I posted a while back (http://www.nortonownersclub.org/noc-chat/technical4-commando-forum/65493698) & I've seen it happen several times before, often on the drive side when the contents of the sludge trap have dried out & hardened after many years of non use, then dislodged & blocked the oilway to that big end when the engine has been put back into service without a strip down.

Regards, Tim

Tim,

just because something is said more than once dosen't necessarily mean it makes sense. The sludge trap design uses centrifugal force to trap unwanted particles from circulating with the oil. It dosen't lubricate the big ends. Once oil has reached the bigend journal cavity then centrifugal force will cause oil to lubricate the big ends through the journal oil ways.

Oil gets to the crankshaft in the first place due to flow created by the pump. If the oil pump is not producing the necessary volume of oil then the big ends will seize. Low oil pressure in a hot engine means something is wrong with an engine component or the design.

The drive side typically highlights problems with the lubrication system because it is further from the oil supply to the crank. If there is low oil flow rate or pressure then at least, with luck, the timing side gets oiled but little remains for the drive side.

To highlight problems caused by a dodgy lubrication system.

BSA A65's and A10's are reported to have drive side big end failure due to timing side main bush wear and the hit and miss oil feed through the timing side bush (where the pumped oil is working against centrifugal force). Oil goes through the crankshaft and then to the big ends, timing side first. Devimead and then SRM crank end feed conversions (just like our Norton twins) apparently cures the problem.

And yet the A7 and A10 standard setup is pretty good. The only problem I have had with lubrication was when theoil pipe departed the external oil filter (which had seemed like a good idea at the time)and the A10 nipped up. All external filters have since been removed.

Previously garry_norton wrote:

My domi seem to be suffering from poor oil pressure. Has anybody any information on what oil pressure I should expect from my oil pump? Have tried several different pumps, even servicing one, and doesn't seem to have improved at all. Many thanks.

Garry

well if you have no change in the oil presser how do you know this , have you a oil presser guage fitted from the timing cover near the presser relief valve . and have you checked this presser relief valve some one may have fitted a stronger spring. the Right spring should be fitted , i would try and re-new the presser relief spring and fittings , and there is no sludge trap in a Norton crankshaft, And sludge traps were fitted to Triumph Crankshafts they were a fine brass cage inside the crankshaft, But Norton does not have its brass cage fittings, Nortons fine Brass sludge trap in the large drain plug under the crankcases . and thats were you find any fine metal particles a tell tall sign of what wearing out. or damage if any,

yours anna j Dixon

Anna,

Ref. to your comments about no sludge trap is incorrect. It's mentioned in the genuine Mk3 workshop manual to clean the crank cheeks and recess in the flywheel of "sludge and foreign matter". Typically the sludge is quite hard and requires scraping out before thoroughly degreasing parts.The large drain plug has a wire mesh which filters oil sucked up by the pump on it's way back to the oil tank.

Simon is entirely correct. The crankshaft sludge trap centifruges particles to the outer edge of the recess hopefully allowing clean oil to circulate to the big ends. I have stripped cranks which have needed some careful chisel work to shift thesludge. I have also seen cranks where the sludge trap is so full that there was only a wormhole left for the oil to travel to the drive side big end. Norton twins do indeed have a sludge trap. And in most cases a crankcase filter.

Previously simon_ratcliff wrote:

Anna,

Ref. to your comments about no sludge trap is incorrect. It's mentioned in the genuine Mk3 workshop manual to clean the crank cheeks and recess in the flywheel of "sludge and foreign matter". Typically the sludge is quite hard and requires scraping out before thoroughly degreasing parts.The large drain plug has a wire mesh which filters oil sucked up by the pump on it's way back to the oil tank.

just because the crankshaft has a large diameter machined hole inside of the crankshaft and collects some particles over time dose not mean its a sludge trap I had crankshaft apart thats been very clean inside other have had a small amount of bits in there, And theses cranks have done thousands of miles, But if you like to fit a nice brass fine gorse in side your crankshaft next time you have it in bits feel free. yours anna j

Simon is entirely correct. The crankshaft sludge trap centrifuges particles to the outer edge of the recess hopefully allowing clean oil to circulate to the big ends. I have stripped cranks which have needed some careful chisel work to shift thesludge. I have also seen cranks where the sludge trap is so full that there was only a worm hole left for the oil to travel to the drive side big hen. Norton twins do indeed have a sludge trap. And in most cases a crankcase filter.

do you mean large end bearing ! well its not a purposely made for this it just works out that way as a centrifuge as oil is under pressure the idea is so oil builds up pressure in this area so the shell bearing have a constant load of oil pressure as the shells float on the oil pressure unlike other engine parts witch are slash feed

Previously anna jeannette Dixon wrote:

just because the crankshaft has a large diameter machined hole inside of the crankshaft and collects some particles over time dose not mean its a sludge trap....

So what would you call the recess machined into the flywheel, which collects heavy particles (carbon from piston ring blow by) lets call it sludge, and prevents these particles from circulating with the oil?

Why would they bother machining a recess?

So that stuff I chiselled out of my crankshaft wasn't sludge because it hasn't got a sludge trap?

In hindsight it did have the consistency of the wife's gravy but I don't know how she managed to get it in there...

See my post above - a full sludge trap (which I am quite sure was an intentional design feature, semantics aside) will leave a worm hole for oil to get to the drive side big (or just for Anna, large) end.

P.S. Let's hope Mrs Rowe doesn't read this thread.

But Anna's point seems to be that the trap is an accident of manufacture rather than a deliberate design item. Since it's there, it acts as a sludge trap. But I don't believe the crank would be less functional if the hole throught the centre was simply a hole - which is surely how the vast majority of internal combustion engine crankshafts are made?And once it does fill up to the level of the hole it ceases to be a trap - so does it then carry on filling up until it's blocked? And, if so, how? If it is eventually self-blocking then it's not exactly a bright idea!

Previously simon_ratcliff wrote:

Previously David Cooper wrote:

But Anna's point seems to be that the trap is an accident of manufacture rather than a deliberate design item. Since it's there, it acts as a sludge trap. But I don't believe the crank would be less functional if the hole throught the centre was simply a hole - which is surely how the vast majority of internal combustion engine crankshafts are made? And once it does fill up to the level of the hole it ceases to be a trap - so does it then carry on filling up until it's blocked? And, if so, how? If it is eventually self-blocking then it's not exactly a bright idea!

There seems to have been quite a few accidents of design then with sludge traps inc. Norton twins, Triumph pre unit and unit twins, BSA unit singles etc.

Sounds like a very good reason for using modern oils which disperse sludge and stop it causing problems. The lubricants in use when our engines were designed used poor quality (Classic?) oils. Sludge formed by unburnt fuel particles and water in the blow-by combustion products,and soot, circulated and when hot turned to a solid mass which blocked oil ways and caused catastrophic failures,( I had an A7 do that on me just after purchase, I couldn't afford a Norton in those days). The sludge trap was an attempt at removing this muck from circulation and with the poor lubricants available at that time you probably needed a complete engine rebuild every year or so.

Cars,of cause, had filters to remove muck and wet sumps where the sludge also collected but caused less harm.

Previously charles_bovington wrote:

Previously simon_ratcliff wrote:

Previously David Cooper wrote:

But Anna's point seems to be that the trap is an accident of manufacture rather than a deliberate design item. Since it's there, it acts as a sludge trap. But I don't believe the crank would be less functional if the hole throught the centre was simply a hole - which is surely how the vast majority of internal combustion engine crankshafts are made? And once it does fill up to the level of the hole it ceases to be a trap - so does it then carry on filling up until it's blocked? And, if so, how? If it is eventually self-blocking then it's not exactly a bright idea!

There seems to have been quite a few accidents of design then with sludge traps inc. Norton twins, Triumph pre unit and unit twins, BSA unit singles etc.

Sounds like a very good reason for using modern oils which disperse sludge and stop it causing problems. The lubricants in use when our engines were designed used poor quality (Classic?) oils. Sludge formed by unburnt fuel particles and water in the blow-by combustion products,and soot, circulated and when hot turned to a solid mass which blocked oil ways and caused catastrophic failures,( I had an A7 do that on me just after purchase, I couldn't afford a Norton in those days). The sludge trap was an attempt at removing this muck from circulation and with the poor lubricants available at that time you probably needed a complete engine rebuild every year or so.

Cars,of cause, had filters to remove muck and wet sumps where the sludge also collected but caused less harm.

Well we need to convert our bike to run On HHO witch will run cleaner with more power and a lot less fuel burnt and it clean the engine too but this is Suppressed technology and we cannot talk about or we get ridiculed . because the big fuel company's want to take every last penny off you.! and they tell you lies too boot and say there fuel its the best way to go it got more ethanol in it, but this bio-ethanol its killing the planet and its animal too do you know or care and about how many orangutans are kill each year because of bio-enthanol they lost-ed there habitat and killed of by plantation workers , now Chris is going to love me for going off topic but is not we getting too a point are about oil .and were it comes from . most oils now a from these plantations the grow she nuts or parm cornell's and to grow this they have to cut down forests all over the world and less Forest more Goble warming the planet cannot cool down so this is why were getting horrible weather So this oil business it killing the planet and Us too So we Need to address the balance, and use less oil get a oil filter you have cleaner oil and convert to hho you have a cleaner engine with less pollutant and better running more mile to the gallon and more money in you pocket in the end and you doing you small bit for a cleaner planet. Hydrogen is the fuel for the future and now, Yours Anna J

Just to add a few more notes to the above carnage. I can not find any mention of the word(s) 'Sludge Trap' in my collection of official Norton documents. However, in the Maintenance Manual and Instruction Book, from the Woolwich Factory, you can read some sensible words of wisdom about servicing the crankshaft and the mention of 'sludge'. Check out the attachment or read the blurb on page 20 yourselves.

Preceding this, on page 12, you will note the mention of a 5 lbs oil pressure in the system, at tickover, when the engine is warm but also a caveat that oil grade and condition can affect this. (the page is too oily to copy)

In my Norton Dominator Performance Portfolio, on page 7, Mr J Moore (Designer) mentions details about the reasons for the large flanges on the crankshaft halves. Later on page 9 he refers to a pressure of 80 psi, to the bigs ends, when the oil is cold. Not bad for the smaller capacity oil pump with a 3-start worm.

Finally........years ago I dismantled a 99 crankshaft that had a 'cricket ball' size lump of hardened sludge inside it. The remaining gap for oil to pass through was roughly 15mm across. Yet it had not spread along the inside of the crankpins.

Purchased an RGM oil pressure test kit a couple of years ago and recorded hot pressure of approx. 5lb/sqin at idle and upto 6,000 rpm approx. 20lb/sqin. Added two shims to the pressure relief valve and pressure went up to 15lb/sqin. and approx. 60lb/sqin. at same rpm. This is using 20/50 synthetic.

The manual pressure Phil qouted of 5lb/sqin. at tickover is, I think, more like what you'd expect for a roller bearing bottom end. Not saying this isn't what you get, just that it seems to indicate an inadequate lubrication system. Does this explain why some owners report cold pressures of e.g 90lb/sqin. and hot of 30lb/sqin? Or is this a down side of single grade oil?

I think much depends on a 3 start or 6 start oil pump gear. Certainly with a 3 start worm and multigrade you get minimal oil pressure when hot. Doesn't bother the engine though.

I think it's already been stated but.......an SAE50 has the same viscosity of a 20w/50 at the same hot engine temperatures - the 20w/50 does not become thinner than an SAE50. Therefore there will be very little difference, if any, in oil pressure.

An SAE50 is thicker than a 20w/50 when cold which is not good for an engine on cold start ups. 20w/50 becoming too thin is a myth perpetuated by an argument with no reference to scientific research. Interesting that Mr Emery has not commented on the subject, as he seems to be one of the main advocates of single grade over multigrade.

In my pragmatic, unscientific, experience despite what is claimed by oilmanufacturers, once an average, well used 99 (mine) got up to workingtemperature in summer, the oil pressure was lower when using multigrade rather than SAE 50. I no longer have the pressure gauge fitted so can't give recent information. Could it be that the air cooled engine running hotter than a water cooled one thinned the multigrade more than a straight oil? Viscosity improvers degrade with use and that could be a factor. Anyway, that's just my what I noticed.

Previously Gordon Johnston wrote:

In my pragmatic, unscientific, experience despite what is claimed by oilmanufacturers, once an average, well used 99 (mine) got up to workingtemperature in summer, the oil pressure was lower when using multigrade rather than SAE 50. I no longer have the pressure gauge fitted so can't give recent information. Could it be that the air cooled engine running hotter than a water cooled one thinned the multigrade more than a straight oil? Viscosity improvers degrade with use and that could be a factor. Anyway, that's just my what I noticed.

OK, so here based on the Science are the facts.

It really is not the case that viscosity index improvers degrade with the sort of use that we put them to, or that bulk oil temperatures in dry sump air cooled engines are higher than those in water cooled wet sump engines.

In an Industry study we ran 30000 mile tests using a range very high revving, high speed 2 and 4 wheel vehicles, with a range of viscosity index improvers and oil viscosities and found very little permanent viscosity loss. This is the basis of the current specifications used by ACEA and also by individual engine manufacturers.

Oil pressure readings can be very deceptive and high values of oil pressure due to high viscosity do not mean that your bearings are properly lubricated as a high proportion of the pump output is dumped in the timing chest.

From hazy memory on a long, hot summer's run. SAE 50 would settle to about 25psi at motorway speeds, 20-50 to 15psi. By the time an oil change was due, the multigrade pressure would have dropped by about 5 psi. As the pressure relief valve was set to open at 80psi, all the oil was going where it should. Certainly the engine was being adequately lubricated in both cases. Funnily enough, I have never had a big end fail on a Norton twin so things can't have been too bad. For the curious, the bike is running on multigrade just now. No strong feelings either way.