The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Dynamo Regulators Mike on 22.05. 2008 09:11

Title: A10 oil filtering
Post by: Dynamo Regulators Mike on 22.05. 2008 09:11
Hello chaps. I am seeking insights into the high oil consumption of my A10.
She has been using about a pint per 200 miles for the last 1000 miles. Full engine rebuild including rebore  to +80 about 1500 miles ago. At the same time the head was done up, with new guides where necessary and valves. After a few hundred miles of topping up the oil and occasional white smoke from the exhausts (more from RHC), I stripped off the top end again, but found nothing at all amiss, except witness of a possible oil path from pushrod tunnel to cylinder on the head gasket. I have checked compression which is good at around 130 psi. (8:1 nominal pistons), and she starts and runs well, pulling like the proverbial train, despite the oil burning. Plugs are black, but Boyer ignition must help here, with the much higher available HT voltage. No significant oil leaks anywhere by the way.
Now, I have an oil filter fitted in the toolbox, the 2CV type. Oil is decent quality 20W50.  I suspect that the filter has a considerable bearing on the oil usage, but I cannot understand why. My suspicion is that the engine is running with excess oil in the cases, i.e. wet sumping. Suspicion is that crankcase oil level is high, so excessive oil on the bores inevitably getting past rings into cylinders. No oil from breather though. Return to tank looks reasonably strong but perhaps not as much included air as I would expect. Focussing in on the oil system, I first checked the oil pressure feed. Maximum cold pressure about 60 psi (SRM regulator valve, with two washers removed, else about 75 psi), with typical hot running pressure 40 psi, which I consider pretty good. Then move gauge to return line, monitoring at rear engine connection. Cold pressure around 20 psi, falling to just off the zero stop, perhaps 2-4 psi after just a few miles. With the filter temporarily replaced with a plain ¼ BSP male-male adaptor, working pressure fell by perhaps 1 psi, just perceptible on the 100 psi guage. But smoke in the exhaust on static revving was definitely less, and oil return to tank appears slightly greater.
Last evening took her on a 50 mile run with filter out of line. No sign of the occasional white smoke. Plugs looking cleaner, and oil level not dropped (but may be too soon to tell). So it looks like a partial result. But why should a pound or two of back pressure make such a difference? A gear type pump is considered to be positive displacement, more or less constant flow at a given speed, so that pressure is a function of flow. I guess I will have to check the pump again, but I did have it apart at the rebuild and it seemed to be in fine fettle then.
Problem is that I really want to have a filter in-line. Perhaps I will try a Vokes WDB40 filter I have on the shelf (picked up a new element for it at Netley Marsh last week for £2). Placed above the gearbox with much shorter total length of line hopefully this will cope better with any small back pressure. No idea of how efficient a filter this small element is compared with the paper canister one, but better than none).
Sorry this is so long, but it really is headache for me. Any suggestions and insights very welcome please. Any other measurements to take? There are other case reported anecdotally where filter in return line has caused problems, including on this forum, but no real explanation as to why, as far as I am aware. On the other hand there are many machines with filters fitted who are getting the benefits of cleaner oil, without apparent hassle.
Please HELP.

Title: Re: A10 oil filtering
Post by: fido on 22.05. 2008 09:29
Welcome to the site, Mike. They tend to recommend cheap oil, changed frequently when running in, to allow the rings to bed in without glazing the bores.  You don't mention your running in regime, sometimes you can cause problems by treating the engine too gently or not varying revs enough. I tend to let the revs go higher on downhill stretches so you can get some variation without stressing the engine too much.
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 22.05. 2008 13:48
Thanks for the welcome Fido. It hadn't occurred that this was my first post here, as I registered a while ago now and have been reading the messages for some time. I placed this post here as this forum seems to provide more considered answers than others. More debate than dictate.

As for running in, I employed supermarket 'Wilko' 20W50 for the first 500 miles or so, before changing oil and filter. Used the engine progressively harder and more revs as mileage progressed. This has always worked for me before. If anything I used it harder earlier this time. My unplanned inspection opportunity after a few hundred miles showed the bores to be running in nicely, with the honing patterns still visible but fading.
Title: Re: A10 oil filtering
Post by: RichardL on 22.05. 2008 15:52
I don't know how often you are riding to accumulate the 200 miles. If it is infrequent. and we assume wetsumping is actually the cause of oil loss, could it be that said wetsumping has occured from the bike sitting, as opposed to failure to scavange the crankcase? It sounds like you are a frequent rider, as I wish I was. However, my bike seems to be in a constant state of building, rebuilding or repair (my fault, not that of the A10 pictured at ).

Title: Re: A10 oil filtering
Post by: a10gf on 22.05. 2008 15:59
manormike wrote
More debate than dictate
That's a good comment, and welcome to the forum. Detailed posts (and good pictures) are welcome and valuable, it gives lot's of practical information to evaluate and learn from.

Good topic this one, I have been thinking about oil filtering (like everybody, I suppose) for my plunger, and hope this thread will provide good info (Am looking for some small filtersystem that works good enough and is safe to use).

Title: Re: A10 oil filtering
Post by: groily on 22.05. 2008 16:01
If there was a lot of oil in the cases, I'd expect, like you, for there to be a fair bit coming out of the breather. It's hard to believe that a return filter could make the difference, but I suppose the extra pressure and plumbing could affect the scavenging a tad as you suggest. And maybe the contents of the filter can trickle back down the return line when the engine is stationary? Is there a ball valve in there to prevent that, I wonder, which the return pump has to keep off its seat? If the return flow is visibly less, it has to be saying something . . .  SRM say - or said to me anyway - that they don't recommend return line filters. Man said 'they could make wet-sumping worse' and then went on to say that any proper filter needs to be on the feed side like a car, and there's no way of doing that. I reckon anything's better than nothing in principle, but his first point may perhaps be valid. Your best bet has to be to run another couple of hundred miles without the filter and see what happens but excess oil in the cases (to some modest degree) does seem the most likely cause, I agree. Good luck!
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 22.05. 2008 18:08
In response to a couple of points raised. The bike has now covered just on 1,700 miles in the five months since its rebuild, just before Christmas. 850 of these were in a trip across Belgium over five days. (Top up oil was really expensive there.) There is little or no drain down on standing but it has rarely stood for more than a week.

Agreed that the ideal place for a filter would be after the feed from the pump but that would mean major surgery. At least fed from a tank of filtered oil the pump should never supplied with debris contaminated oil, which would be otherwise be the case. Sounds like the SRM man has direct experience of filters adding to oil system ills. The Vokes filter  was fitted to the 1954 Daytona winning bikes so there can?t be any fundamental problem with a return line installation. There is a non-return ball valve in the sump pickup pipe so the filter should not drain back, at least not too rapidly. That ball and seat are not accessible even after a full strip down, unlike the anti drain ball valve behind the pump, between the crankcases.

I have now replaced the long pipes to the toolbox with an standard length return pipe. Latter is about 18? long vs. 54?. So three times the pressure loss in the pipe alone. No wonder the filter?s contributing to pressure drop was smaller in comparison. Cold pressure drop read less than 10 psi, falling very rapidly.

Clearly a larger flow of oil in the engine will occur at higher engine speeds. At steady speed the scavenge side should also have proportionately larger capacity so all is well. But there will be a lag on slowing down as the oil flows down to the sump. Under this condition it has occurred to me that the scavenge side has most work to do. Its additional capacity compared with the feed side may well be exceeded transiently. If this is made significantly worse by the return line flow resistance then crankcase level will rise and more oil would likely be burnt until the pump catches up. I have noticed that occasionally an increase of smoke occurs on slowing after a relatively fast run. But it comes back to why scavenge flow may be affected by working against a small pressure head. Perhaps the entrained air in the system complicates matters further in some way.

I will continue to run without the filter for at least long enough to see if oil consumption has indeed fallen. And will also think about how I might install the WDB40 filter. It should fit under the ?ski-slope? which would add minimal oil line length so perhaps tolerable pressure drop for the best of all worlds. But there are other jobs to do on the bike (as always Manorsound), not to say on house and garden. Will let you know how it goes.   
Title: Re: A10 oil filtering
Post by: fido on 23.05. 2008 07:35
Could you have a leak at the oil pump gasket?
Title: Re: A10 oil filtering
Post by: groily on 23.05. 2008 07:36
Reckon your thinking is hard to beat. But it's very surprising to me that the scavenge pump is that sensitive to volume and a smidgeon of pressure, be it from the filter or the line length, as I have always assumed scavenge pumps can cope with almost anything. Appears that things are more delicately balanced than one might think . . . be fascinated to hear more in due course. Maybe a change of filter type, as you propose, will sort it. Other people here have been running return side filters, so perhaps they'll chime in with comments based on experience . . . I'm quite glad I've held back on that front!
Title: Re: A10 oil filtering
Post by: LJ. on 23.05. 2008 09:35
Yep! I also had given the oil filter a try on my A10s system, I have to admit it does make sense in theory to use 20/50 and filter but I found my bike just did not like it. I cant remember if the bike used any more oil than normal but it did chuck out a lot of fine oily mist out of the breather. That is one of the main reasons for reverting back to standard, (turbulance was messing up clothing) no filter and use of straight 40 oil, no problem since. What is it that we are afraid of here to want to use a filter and 20/50 I have to ask? There have been many bikes covering thousands of miles without filters, ok sludge traps may get filled but then... A strip down is deserved after such long and loyal reliablitily. I can well do without the fuss and hassle that some seem to have, and indeed like I had during my experiments.

I sometimes wonder just what the expected mileage BSA hoped for in designing and building these machines. They have obviously done very well, hence so many are still around and running.

If it wasn't for other factors I think the best answer must be to use a cheap 20/50 with no filter and change the oil at no more than 500 miles, but this being a thinner oil would raise the risk of giving leaks. My own preference is to use Castrol XXL40 being thicker I dont get any leaks at all and with the engine being baked in the oil it does smell very classy and gives a highly pleasing aroma! (you can tell I'm not an engineer)  *eek*  *lol*
Title: Re: A10 oil filtering
Post by: bsa-bill on 23.05. 2008 10:40
Just to put an opposing view, I have a filter ( return side ) - non return valve and use 20/50 without problems at all.
I don't get to ride as often as I would like though.
Only thing I get (along with quite a few others ) is a bit of smoke on one side after starting, it clears in a very short time.
It is not always the same side that smokes - leads me to believe it's valve guides, something which has not been mentioned in this thread so far?

All the best - Bill
Title: Re: A10 oil filtering
Post by: groily on 23.05. 2008 12:53
well, it starts to sound, per LJ, as if the installation of some sorts of filter can in certain cases cause an increase in crankcase oil level when the motor's running. In principle having a filter, even on the return, has to be better than not but I am sure there are loads of engines out there that have done a gazillion on the same crank without one.
I use modern 20/50 in all engines with plain big ends as long as I know the cranks are clean inside; and straight grade for roller b/ends. Some engines seem to last for ever or near enough, others less. Probably a lot to do with the quality of regrinds, assembly etc. I change oil every 1000 miles out of habit.
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 24.05. 2008 14:52
Have put in another 60 miles with no filter. Still too early to be sure of oil consumption but no smoke at all seen, despite bursts of hard riding. But I do feel slightly uncomfortable running without the protection potential of a filter. Trouble is that I am an engineer, and specialise in Condition Monitoring via wear debris monitoring of oil. Oil filters have been fitted in the car world for many decades and have been common in production motorcycle engines since the ?60?s. It is very well established that it is especially valuable to filter out debris in engines with plain bearings, and our BSA?s have more than their share; timing side main and big ends. If an engine lasts say 10,000 miles without filtering then it is reasonable to expect 20 k miles to wear to the same degree kitted out with a filter that removes most particulate of a size comparable to bearing oil film thickness. And it means I can safely use quality multigrade oil, which are more available and less expensive than the straight stuff longterm. But this is not another oil thread.  *eek*

An engineer?s curiosity driven nature and attraction to problem solving leads people like me to spend arguably too much time and effort in ?improvement?. But it is more fun and rewarding than another expensive routine rebuild. A key aspect of the Classic Bike pastime as far as I am concerned. Perhaps it has the same perverse attraction to me, that maintaining and fettling original style voltage regulator box has to you LJ, when a modern fit and forget alternative is readily available. ;)

Hoping to buy a lower range pressure gauge soon in readiness to closely monitor pressure heads whilst experimenting with the WDB40 filter. Will also take a close look at the oil pump when I get the chance to see if that is at all suspect. Now I recall speaking to an ex Small Heath apprentice who recounted experimental work with the gear pumps. There were apparently some counterintuitive findings regarding efficiency. Another interesting area to explore.  *smile*
Title: Re: A10 oil filtering
Post by: groily on 24.05. 2008 17:39
While I was knocking off my usual Saturday miles on the A10 this am I was wondering about the oil level in your tank Mike. (Makes a change from worrying about mine.) With the filter, was the level lower than you'd have expected after a run, which would indicate that the level of oil in the cases was too high, I wonder? If you have a drain plug, I wonder did you ever drain the thing to see what came out just after a run, when the filter was fitted? And is the level more constant, higher, whatever, now you're filter-less again? Just idle ponderings, I seem to think about oil levels far too often! At least I don't have to think about dodgy voltage regulators any more! Wet day for it too . . . lights on all the time
Title: Re: A10 oil filtering
Post by: LJ. on 24.05. 2008 19:45
It's a very fair comment you make Mike about the engineers interests in oil on an A10 and I do look forward to hearing of a successful remedy from someone soon especially if its from discussions held here on the A7 & A10 forum. The way oil prices are going, and I wonder how long we will all be moaning about the price of engine oil like the price of Petrol here in the UK, I too would certainly move over from the rather expensive straight 40 Castrol oil to a multi and filter.

The discussion is puzzling, we are aware of back pressure because of filters and maybe longer oil pipe lines etc. I wonder how the pump manages with Straight 50 oil which is even thicker than 40 or multigrades. Surely the 50 grade is causing back pressure also, particularly when cold.

By the way... I am begining to wonder if your also known as 'Blue Flash' on another forum? If so, great to have you here! The 8" front wheel hub from you has just been 'spoked and rimmed' and has been running again the last couple of days (Many thanks again for that)... What a difference from the 7" front brake.

Back to Oil filtering  :!
Title: Re: A10 oil filtering
Post by: dpaddock on 24.05. 2008 23:03
I, too, am an engineer, retired now for some three years, with four grandchildren, a lovely wife, and a '57 Spitfire plus a '60 Goldie. With bikes like these, I want every bit of protection I can get, including engine oil.

I recently fitted a Ducati engine oil filter system to the Spit, and got quite a bit of wet sump. I attribute this to filter housing siphoning (at this time); I'll study this and get back to you.
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 25.05. 2008 11:24
Laurence, indeed I also go by the soubriquet 'Blue Flash' elsewhere. Obviously from the bike, (now appearing left  ????), but also with an electrical connotation. Pleased to know the wheel hub is back in use after 20 plus years and is giving improved braking (,safety and enjoyment).

The suspicion of slight back pressure in the return line causing problems is truly puzzling. 20W50 at working temperature should have similar viscosity to straight 50. However when cold the 50 will see much larger resistance which does not normally cause any issue with sump build up. With long return line and filter might expect cooling effect to increase back pressure, but again less of a problem with multigrade.

Another faint possibility is that the filter changes the aeration of the oil significantly. Not the proportion of air to oil, but the size of the bubbles. Then assuming larger bubbles with filter these will leave the oil in the tank more rapidly. Then the feed pump is supplied with less aerated oil increasing oil flow rate compared with no filter. Then the scavenge side has to do more work and runs out of capacity under some conditions. Clutching at straws maybe.

Bill or I should say Groily, the oil level in the tank does not appear consistently lower with filter, and I have been keeping a close watch on this. Also the times I have drained the sump I have not measured more than 5 fl oz, but this is always after slow couple of miles running back through residential roads. Now a level sensor in the tank logging against engine speed and perhaps oil temperature would be very interesting. But beyond  me at present.

Glad to see another engineer entering the discussion with a similar problem with a filter. Look forward to your input dpaddock. I should add at this stage that I am an electronics engineer, but the same sort of enquiring mindset still applies.
Title: Re: A10 oil filtering
Post by: bsa-bill on 25.05. 2008 13:00
before I fitted my filter I wondered about back pressure but after trying the thing by fitting the filter up ( Citreon element ) and blowing through it I was amazed at the lack of any resistance really, all right blowing through it is not the same as forcing liquid through it on the other hand the pump feed side should develop 60 plus lb/in so the scavenge side should do the same at least if it had to.
I tend to think the problem lies elsewhere, be nice to know for sure though.

All the best - Bill
Title: Re: A10 oil filtering
Post by: RichardL on 25.05. 2008 15:05

Interesting concept, that of larger bubbles dissipating faster, thus causing the pump to deliver more actual oil. I'm not sure I understand why the filter would make the bubbles larger. It seems the intuitive opposite, but, I suspect you have considered this more than I and have a good explanation.

Regarding the scavenge side sucking up the same amount as the feed side delivers, ultimately, this is trying to happen, but the circumstances by which this happens are different for the two functions. The feed side has the benefit of constant atmospheric pressure in the tank and gravity sending oil toward the pump. The scavenge side must depend on siphon created by the pump, as allowed by air pressure in the crankcase, which, in turn,  is dependent on pressure allowed in and out by the breather. As we know, the breather is infrequently open. Is it not possible that the inefficiecy of siphoning versus gravity (as helped by atmospheric pressure) makes the back pressure of the lines and filter more critical, particularly if the action of siphoning, itself, is normally contributing to reducing crankcase air pressure? Though I have no confirmation  from previous discussion in this forum, I am convinced that the main purpose of the breather is to create near-normal atmospheric pressure in the crankcase so that oil can be pumped in and drawn out.

Another aspect that has received little comment here is valve guides.  Bill suggested this as a possibiliity, believing they had not been mentioned. Going back, we see that you had the head rebuilt, including guides. For my understanding, guides would have been a more obvious and direct source of oil loss than excess oil on the backside of the oil scraper ring. Having new guides does not guarantee that they fit properly. However, I suppose that if it were guides, smoke would be more continuous. 

I trust that I have only ventured into things I understand while attempting to make it sound like I understand that of which I speak. Nevertheless, I always appreciate being set straight when I've strayed from the path.


P.S. As an electronics engineer (I believe in the UK), perhaps you can help me on another issue completely. My work requires me to understand a bit about 3-phase electrical power in the UK/EU. So, my question is: should I refer to UK 3-phase as 240/415 VAC, 230/400 VAC or somethng else completely. Anyone else knowing the answer, please feel free to jump in. Sorry, if this strays too far from our prime directive of exploring the exotic world of A7/10's. 

P.P.S. I modified my P.S., after-the-fact, to more closely resemble how we in the U.S. might rever to 3-phase, as in "120/208" (phase-to-neutral/phase-to-phase). Now I really have tortured the reader's patience for miles-off-topic.   

Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 26.05. 2008 12:45
Hello again Richard a.k.a. manosound and sorry I spelled the name wrong last time. Only guessing that the filter would increase bubble size. No evidence but I just feel that a low aerated oil flow passing through a large area membrane would provide a good surface for the air to coalesce.

Whatever the subtleties with regard to oil pumping on either side of the pump, it clearly only takes a little change to make a good difference, i.e. fitting an oil filter providing minimal back pressure. I too am sure that the breather is contrived to maintain atmospheric or a slight vacuum in the cases. This in turn reduces oil leakage and reduces power loss. Surprises me how well it seems to work given that the air passage is such a low diameter and fairly torturous.

The valve ? guide fit in my engine was indeed within limits at the rebuild. Worn guides will puff smoke particularly on the overrun I am led to believe, as any excess oil is forced into the lower pressure in the cylinder. Also difficult to see how this would be affected by filter. If anything oil feed to the head would be less, due to pressure drop.

One little addition to this oil thread from me. I have 2 spare oil pumps in the garage which I thought were the same. However the gear tooth profiles are different. Wondering which one is the earlier and when and why the change was made. Could be performance but may equally have been for cost reasons.

P.S. with regard to your 3 phase question I am afraid this is not a familiar are to me, but is it not the phase to phase voltage that is normally used?
Title: Re: A10 oil filtering
Post by: RichardL on 26.05. 2008 14:23
Mike, et al,

This is all so interesting and, perhaps, not that important if removing the filter solves the problem and you are riding happy. Nevertheless, "inquiring minds want to know."  I don't know if you are old enough to remember the Groucho Marx Show, or if it was even shown in the United Kingdom. Nevertheless, I suppose it is enough in the popular culture that you may understand my reference when I say "'Coalesce' is the secret word, you've one a hundred dollars!  O.K., get rid of the duck!" Yes, I can envision how the bubbles would coalesce on the input side of the filter. Now that I'm thinking about it, it seems that that would not lead to larger bubbles on the output side. Instead, only those small enough to permeate the pore size of the filter would get through, meaning, nearly no bubbles. What jumps out in this, at least to me, is that coalescing of bubbles on the input side of the filter may lead to really big bubbles in the return line, upstream of the filter, the affects of which I am not certain.

The change in pump gear profile is very interesting. I am off to the shed to open up my pumps to see which I have.


P.S.  I have seen where phase-to-phase is listed for UK/EU 3-phahse connectors. I suppose this is a way of rating the plastic or identifying the pin/socket shape or arrangement.

Title: Re: A10 oil filtering
Post by: G/F DAVE on 26.05. 2008 21:19
I have run a cartridge type filter & used 20/50 multigrade on my A10 plunger with no problems concerning oil usage.The scavenge side of the A7/A10 oil pump is of greater capacity than the feed, this is why you can see froth (bubbles) on return side if you peer into oil tank. Personally I think your problem with oil lies elsewhere.I would not run a plain bearing motor without a suitable filter & dont see the reason why such "experts" as SRM dont recommend them on the return to the tank .I also use this type of filter on my pre-unit TRIUMPH motor with plunger type oil pump also with no problems. I use a alloy sump plate with magnetic plug ,now this is always free of particles between oil changes .You take your chances when using the standard tea strainer filters as fitted by BSA which in turn must clog sludge trap quicker hence reduced oil pressure feed to big ends. BANG!!!!!   *doh* *doh*.ALL THE BEST G/F DAVE...
Title: Re: A10 oil filtering
Post by: RichardL on 26.05. 2008 23:29

Can you tell us who made your cartridge filter and how you adapted from the armored lines to whatever thread is on the filter?


Title: Re: A10 oil filtering
Post by: G/F DAVE on 27.05. 2008 10:11
Hi, Richard filter housing is a cast alloy one made by RGM that takes a citreon/harley spin on cartridge(check out ebay site ). Plumbing into the system is simple enough as on plunger A10,s oil union is connected to oil tank by rubber pipes .I have made a bracket that bolts to frame under the oil tank to mount filter .Filter housing has push on fittings so no threads just hose clips. Just make up extra length of pipe work ..easy..I think these filters were originaly made for norton commandos. If you need to fit one of these on a A10 swing arm model you just need new unions & pipe work for return side leaving feed pipe alone.I really can,t see these kits causing any problems only improvements. Also I know people that use oil cooler kits fitted at front of their frames, now with all that extra pipe work these must make extra work for the oil pump.But again they say no problems,I,m going to fit one of these to my TRI-BSA as on hot days (when we get them) will help keep motor cool in traffic also will gain extra oil capacity. Regards G/F DAVE..
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 27.06. 2008 11:48
I now have more to add to this thread after further mulling over and experimentation regarding my problem of increased oil consumption and frequent smoking on my A10 with return line filter fitted. I have carried out various tests both on the bike and on the work bench to try to get to the bottom of this. The world is divided into those who have seen problems with an return line filter fitted and those who have not.

Firstly using a borrowed gauge I confirmed that the scavenge pump vacuum was adequate and that there were no leaks to compromise oil pick up. A 0.9 Bar suck was seen. Then I borrowed a test block from local engineer, Bob Light, (of Hi-de-Hi filter fame) who used it in comparing performance of a series of A10 pumps, which work was presented in the BSAOC Star magazine. The block was set up to allow my small lathe to drive to the pump at an indicated speed, and provides convenient plumbing connections. The pump block becomes the heart of an investigative lubrication system employing a C15 oil tank and small plastic tray to represent the engine sump. A picture is attached with the pump partly obscured by a cover to catch much of the oil / grease flung from the worm drive. The pump I used for these tests was prepared by flatting the end plates and turned freely by thumb. Nothing special, just not brand new or completely shot, therefore hopefully representing a typical pump. The red plastic nozzle at the feed line outlet speeds the flow velocity giving a bit of a splash to include a little air, incidentally providing a small back pressure for the feed gears.

First the feed side pumping rate was measured as 4.3 cc per second @1000 rpm, and the return side 6.45 cc/s (from time to fill to a level mark in a jug). So this pump has 50% more return capacity than feed. Compare with a gear width ratio of 7/16? to 5/16?, suggesting a 40% higher capacity. Then I fitted a Vokes WDB40 filter in the return line. With the system running for a period of 10 minutes or so the overall aeration of oil in the loop increased, a very interesting finding. I then swapped the Vokes for the 2CV type formerly fitted to the bike. This filter again increased aeration after a good period of running, but not by as much as the smaller filter element.

The rocker feed flow proportion measured some 20% of the total flow in the return line (with open tube ? no rockers). With this returned to the plastic tray ?sump? as in the real system, the rate of clearance of extra oil poured into the tray fell markedly. This observation set me thinking. What if the rocker feed on my engine is too high? It has a silly old ?go faster? cast alloy finned rocker feed in place of the standard banjos. Is this less restrictive to oil flow? I fitted a piece of clear tube to the top end feed; there appeared to be no air inclusion and flow seems quite fast in the tube. If too much oil getting to top end then could be losing oil down valve guides (valves and guides replaced as necessary only 2k miles ago so not worn), and there would be a pronounced lag before the excess reached the sump to be scavenged. Maybe this could be part of why the exhaust more likely to smoke for a while after slowing down?

More questions than answers at this stage. Would like to see how the flow rates of the pump currently on my bike compares  with the one on the test rig. Where does change in aeration with filter fit into all this? My suspicion is that air inclusion has more effect that a couple of PSI backpressure on the scavenge pump. Different oils have different foaming characteristics. Anti-foaming is probably one of the additives skimped on with cheaper oil, and I am using cheap 20W50 for these tests. How typical is my rocker feed rate? It is easy to see a lot a variables here. Ratio of the tank stand pipe aperture compared with restricting holes in the rocker feed plumbing will affect proportion of oil to sump via rockers. Much of my testing was done at a convenient 1,500 rpm, a bit slow perhaps on reflection.

Hope this is still of some interest to forum members, it does all seem a long way away from the joys of pre-unit twin owning. But I just want to achieve the best reliability of the engine so I can ride it for thousand mile or more trips without concern or undue spannering. If anyone has details of standard rocker feed restrictions and dimensions I would very interested. (That was a question that came up somewhere on a message board recently but I could not find it again.) Any other suggestions while I am at it?


Title: Re: A10 oil filtering
Post by: LJ. on 27.06. 2008 13:08
This is very interesting stuff Mike thanks for putting the time in and writing up this for members to see.

I wonder if you also intend to try out different oils to see what results are obtained from them?

Please do keep us further updated of your progress.
Title: Re: A10 oil filtering
Post by: a10gf on 27.06. 2008 19:03
Mike, impressive work ! And absolutely interesting.
Title: Re: A10 oil filtering
Post by: RichardL on 27.06. 2008 21:01

Your thorough writing is not in vain. It is very interesting reading. I was thinking of trying something similar to see what the pressure output of the pump is at various RPM, however, I have neither thr lathe facility, pump block or, right now, time. In thinking about pressure, it occurs to me that to find that out for a given bike, it must be tested on the running bike, as each engine presents its own back pressure. Perhaps the "suck" is even more out of proportion, considering the delivery must make it through the entire maze of passages (including the oh-so-tight route through the crank). If this were true it would opt against wet sumping while running.

Regarding 1000-mile trips on an A10, not that I ever expect to come close to that, but my experience thus far would say that it might wear out the kidneys before the engine.

Title: Re: A10 oil filtering
Post by: england kev on 28.06. 2008 11:22
In principle having a filter, even on the return, has to be better than not


These engines were designed by engineers not to have a filter, so why do we assume they would be better now with one.
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 28.06. 2008 12:30
Hi all, thanks for the words of encouragement.
Kev, the reason to fit a filter is to prolong engine life. Much engine wear is caused by initial wear particles circulating time and time again through bearing clearances and doing more harm, creating more wear. Known as regenerative wear in the trade. Engineers have known this for a very long time, and filters have therefore been fitted in many oil systems for a long time. Bert Hopwood, a key designer of our twins, or at laest his developmewnt team knew the benefits in the '50's. To illustrate, the BSA Daytona race winning bikes were fitted with additional external filters. But the cost accountants would not see it the same way. Added production costs and a more durable product does not help sell new machines.
Of course our lower revving engines last pretty well anyway but seems to me that longer yet intervals between precious rebores can only be good. It also means that modern oils can be used to better effect and changed less often. But that leads into other complex areas with as many opinions as voices. *eek*
LJ, I would test with other oils but the cost of doing it puts me off. Donations of oil samples for test welcome, about 4 pints is enough. ;)
Richard, the maximum suck capacity does not come into play in normal conditions unless testing for leaks. The crankcase pressure should be near atmospheric (mine measued at 2 to 3 inches of mercury under atmospheric from idle to a big handful of revs). The pumps removes the sump oil /air at a rate determined by the volume swept by its gears, hopefully a good bit faster than the rate of oil drain to the sump under steady conditions. But internal leakage in the pump will play a part, as it does on the higher pressure feed side. Leakage should be much less, I guess, with minimal pressure difference.
Hoping to remove the oil pump from the bike and set it up on the rig this weekend.
Will continue to post findings with the all important numbers where possible.
Title: Re: A10 oil filtering
Post by: a10gf on 28.06. 2008 13:46
All this triggers my old idea. Looking at the filter fitted to my Yamaha XT 350, a very fine and very small mesh filter which seems to do the job perfectly. I think the same goes on XT650. The mesh must be 10 times finer than the original a10, should stop most, if not all, of any damaging particles (certainly does so in the Yamaha). It can be cleaned and kept "forever" if not damaged.

I have for years been thinking about making a container with fittings for some in-out hose connection for the A10. This would all in all be very small, and I think the return flow capacity would not suffer in any way.

I've had a large car-type filtersystem lying around for years, feel it's too big, ugly and difficult to fit properly anywhere, and need much longer hosing etc.

The envisaged filter enclosing would be around 5cm dia / 6cm long + hose connections protrubing.

Maybe worth investigating further? I already see a nice unobtrusive brass cannister fitted, polished and shiny  *smile*
Title: Re: A10 oil filtering
Post by: bsa-bill on 28.06. 2008 13:50
England Kev - these engines were designed with a filter, it is situated in the centre of the crank and needs cleaned out , not easy at all,  remember the engines were also designed before the today's readily available detergent oils.
A light detergent oil and a easily changed filter has got to be an improvement and was incorporated in later classic bikes by the designers.

All the best - Bill
Title: Re: A10 oil filtering
Post by: jfligg on 29.06. 2008 13:26
Hi Mike
  First off I would like to say thanks for your extra effort on this topic... Cheers.  I think my biggest concern about a return inline filter is the over oiling to the rockers and the reduction of the amount of oil in the scavenge.  How would this be affected after longer running periods?  Would the sump eventually run dry?  This my fear.  I would think the likelyness of this hapening is low as if it happened to a few people you would hear about it on the various forums.  I am still running my Star Twin with out a filter and using a str 50w that is changed every 700 miles.  Once again Mike Thanks and keep up the good work. Jeff 
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 01.07. 2008 15:33
a10gf, that Yammy filter is not so different in size to the WDB40 element, which is about 5cm long and 4cm diameter. Are they cheap and easy to get? If so would be interesting to see if it could be fitted into the Vokes canister; I was lucky to pick up one original element for just £2 recently but don't think they are generally easy to find (unless anyone knows different?). As you say much neater. Does this filter have a through hole or a plain end and it looks like paper?

jfligg, I am not with you with regard to a return line filter over oiling the rockers. But this would be the case if the rocker feed was taken off before the filter. On the A7/10 setup the rocker oil effectively adds oil to the sump, albeit after a delay while it finds its way from top to the sump plate. This will increase the tendency to wet sumping s the scavenge has more volume to cope with.

I have now compared the pump I have been taking the measurements with, with the one from my A10. They both show very similar volume flow. Scavenge about 40% higher than feed after careful comparison at 1500 rpm. I was surprised to see that the one from the bike had the 'petal' shaped teeth, whilst the initial test one has the 'involute' tooth shape, (see photo earlier in this thread). This appears to rule out the change as being for performance improvement.

Can't see where else to go to find an explanation for my smoky exhaust and oil consumption *conf*, unless the rocker feed on my machine is higher than it should be. I think I will fit the involute tooth pump back on the bike (the other appeared to have a flaw on one tooth which might be a weak area). See if that does make any difference on the bike. Then at least temporarily restrict the rocker flow to see if that changes things any.
Title: Re: A10 oil filtering
Post by: dpaddock on 01.07. 2008 17:41
Mike is certainly doing good things, here!
I mentioned in my 25 May posting that I had significant sump oil after fitting and running with the Ducati filter. Actually, it was no more than I typically get (50 ml to 175 ml) and the filter can was full (100 ml). So drain-back is not a relevant factor.
Re rocker oil feed: the flow to the rockers is dictated by the size of the drillings in the banjo screws. The rockers really can't be "over-oiled" unless the return line gets severely restricted downstream from the tee. In which case, I'd expect to see oil spurting from the return line somewhere.
Incidentally, 1000 rpm on the pump in Mike's setup is 3200 engine rpm.
Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 01.07. 2008 19:25
dpaddock, do you know what size the feed holes in the standard banjo bolts are? As I say, mine has a non-standard 'go-faster' rocker feed and I wonder if these are drilled the same.

You can't see it in the picture of my set up, but the lathe drives the pump worm via a gear as fitted to the crankshaft. So the speed of the lathe as given is equivalent to the engine crank speed.


Title: Re: A10 oil filtering
Post by: a10gf on 01.07. 2008 23:31
Mike wrote
Does this filter have a through hole or a plain end and it looks like paper?

It's fed from the whole outside area trough the mesh, with a central outlet on one end, a springloaded bypass valve on the other. Very,very fine metal mesh. Available from any yamaha dealer afaik. And it's reusable, forever as I see it, just clean away whatever may have accumulated on the outside of it with a brush and some petrol. It's really a neat little device.
Title: Re: A10 oil filtering
Post by: dpaddock on 02.07. 2008 12:23
"dpaddock, do you know what size the feed holes in the standard banjo bolts are? As I say, mine has a non-standard 'go-faster' rocker feed and I wonder if these are drilled the same."

Mike, the feed (radial) hole in the banjo screw is .046" (~3/64"). This is the orifice that determines the flow rate.

Pump drive noted. Thanks.

Title: Rocker Feed Banjo Bolts
Post by: RichardL on 14.08. 2008 18:08
"dpaddock, do you know what size the feed holes in the standard banjo bolts are? ....Mike, the feed (radial) hole in the banjo screw is .046" (~3/64"). This is the orifice that determines the flow rate.


The radial holes in my banjo bolts are different from each other. One is larger (for feed, I assume) and one is quite small (for venting, I assume). Does this sound correct and, if so, does it matter which one is forward and which is rear?

Title: Re: A10 oil filtering
Post by: Dynamo Regulators Mike on 14.08. 2008 19:18
I recently found out that the feed holes are differently sized on Goldies. Larger for exhaust I believe because it runs so much hotter. So this could also be the case for twins? Is one smaller or larger than 3/64"?
Back to packing for the International, leaving 8 a.m. tomorrow, and the eather looks ok for once
Title: Re: A10 oil filtering
Post by: wdco42 on 06.09. 2008 20:02

I have recently seen a friend's 850 Commando, and the bike has in original equipment a cartridge filter, like the one you speek. The interesting detail is that it is fitted BEHIND the gearbox, under the bottom oil tank level, and not in an upper position, althought there would be a lot of place... (not speaking about the mud there and the difficulty to change it)

The idea is that Norton's people had the same troubles as your's, and even with upgraded, and simpler (in comparison with the A10) oiling system, there was no other solution to locate the filter, and make it work properly...

I intend to fit a filter, the cartridge type (I'm french, and the cartridge is the same as 2CV Citroën), but will try to locate it as it is allways "submerged" by oil.

Cheers, Claude
Title: Re: A10 oil filtering
Post by: dpaddock on 07.09. 2008 23:01
It matters not where the oil filter is vertically installed; this is a closed positive displacement system.
We've already discussed the over-oiling rockers matter - it doesn't exist as long as you are using 3/64-inch diameter radial rocker banjo bolts. [Yes, Gold Stars use a larger diameter exhaust bolt feed, but that's because the Goldie exhaust valve is bigger and more severely punished in racing duty (its recommended racing life in this service is about 20 hours).]
So, unless you are going racing, stick with the factory bits.
The Ducati-type filter fitted to my A10 is mounted in the return line after the rocker feed, up high, where I can get to it. It works fine.

Title: Re: A10 oil filtering
Post by: alanp on 22.11. 2009 11:03
I know this is an old thread but it is of interest to me since I'm determined to make the best technical effort in rebuilding the A10/big valve engine I've acquired.
The first point I want to raise concerns the rocker feed banjo bolt hole diameter which, dpaddock stated on 2 July 08, should be .046" diameter. Fitted to my engine they are both close to 2mm (.080"). This represent 3 times the flow volume by area!!! Now I know the scavenge side of the pump can cope with clearing this from the sump but this engine has a history of consuming oil and smoking so maybe it would put excess oil into the rocker box and pass more oil than usual down the valve guides. I'm not being cheeky but dpaddock are you absolutely sure it's .046"dia ?
The second point concerns the after market filters fitted to the return line. There was a comment I think by someone about this increasing the return pressure and hence flow to the rockers, but I thought that the line from the filter return connects to the oil tank return at the same point as the original pipework and hence the rocker feed line is after the filter and not affected by back pressure at the filter inlet. Having not yet bought the filter kit, could someone clarify this for me please, I certainly don't want to increase oil pressure to the rocker box!