Filter in Oil Feed Line

[Alan @Ncl]

As a new forum member I must first say how impressed I am by the quantity and quality of the information and discussion presented on this site. 

I have a 1957 Goldflash that I rescued as a partial machine back in 1975.  I then completely rebuilt it using parts from wherever I could get them so its not exactly standard.  For the past 15 years the bike has stood in the back of the garage, completely ignored and without turning a crank but I have recently set about returning my old friend to its former glory. 

I am now getting near the point of attempting to start the engine following this long period of total neglect.  I have provisionally dealt with some magneto and fuel problems (more of that later) but my immediate concern is with lubrication.  When I rebuilt the bike back in 1975, I made up and installed a cartridge type oil filter and located this underneath the oil tank near the centre-stand where it is hardly visible.  However, THIS FILTER IS INSERTED IN THE FEED TO THE MAIN OIL PUMP, rather than in the return (the latter seems to be almost universally the normal approach, as far as I can see in your threads).  It is interesting that back in the 70s, the advice I was getting was to place the filter in the feed but to be careful to select only a filter that did not contain any kind of ball valve or other potential restriction. I ran for years (not huge miles though) on Castrol GTX, with this arrangement, and never had any problems (except for wetsumpiing of course, if stood for long intervals). Having fitted a draincock on the sump plate this was not really a major problem; only an inconvenience.

Having recently thoroughly cleaned out the oil tank I have now been persuaded by the local classic bike guru to invest in some very expensive modern monograde SAE 40 oil (which also includes a detergent, I note).  The bike is certainly not wetsumping to any degree now and I instinctively like the idea of this nice, customised sticky grade 40 stuff adhering to those good old bushes and bearings.  However,I am worried that the added viscosity may prove problematic for the pump when pulling the oil through the filter, especially when cold.

And so to my question.  Should I ?bin? the expensive oil and go back to 20/50 or should I move the filter into the return line and retain the fancy oil (or perhaps replumb the filter but still go back to 20/50 as well)?.  Any ?words from the wise? would be much appreciated as I think the situation I have described is slightly different to those that have appeared in the past.

[muskrat]

G'day Alan, welcome to the forum.
                                              Move the filter to the return line, most important not to have any restriction on the feed. Oils seems to be a personal thing. I use 20/50 and add Nulon.
Bet you can't wait to throw a leg over her again after so long.
Cheers

[LJ.]

Hello Alan... Nice of you to join us, hope you get a lot of pleasure here.

I think the thick SAE 40 oil and filter is asking a bit much, especially as you say in cold weather. I think it's best to stick with either the filter on return with 20/50 or go straight 40 with no filter and change oil regularly like I do. I agree entirely with what you say about that satisfying... "I instinctively like the idea of this nice, customised sticky grade 40 stuff adhering to those good old bushes and bearings." Spot on! when I look in the tank at 20/50 I don't really feel very confident about a watery looking lubricant when tank is sloshed from side to side. Actually I have been using XXXL50 but will go 40 when I get the next 25 litre drum from Castrol.

Just my opinion, let the oil wars begin! 

[bsa-bill]

Hi Alan and welcome
My thoughts oil wise, on a rebuilt motor ( sludge trap cleaned, engine flushed) 20/50 or modern oil of choice every time, but not in a motor that still has a sludge trap and oil-ways lined with engine cholesterol.
But do be careful with so called straight oils as some do contain detergent ( as you have said), detergent will release any crud to float around the system, OK this is why you have a filter but it's not designed to handle a backlog of stuff !!!

[brackenfel]

Hi Alan,
Welcome to the Forum.. In my limited time here I have found this to be a wonderfully informative, friendly and helpful place, I hope you find the same..

As for oil I have a very good friend who recommends 20/50 for everything but I have my doubts..

A long while ago I had a Laverda 500 and the then guru (sadly now deceased) recommended Solkolene Race Lube 40 (a straight oil with some detergent content). I bought every can I could find as it was often been sold off relatively cheaply as there wasn't much demand! I then sold the Laverda and have since used it in my Velo for years. My A10 doesn't have a filter fitted but I intend to use the straight 40 when I refill shortly and will probably also use it for the B33.. The Velo oil gets very dirty but it does have a fabric filter (in the return). I have no doubt that the detergent is removing the crud but (touch wood!) so far with no catastrophic effects....

I have a Laverda 750 which I filled with Duckhams Q20/50 and when it ticks over more slowly than it should the oil light flickers so that's getting the 40 in the Spring too..

A long time ago I was told that straight oils were best for engines full of roller bearings (inc big end) like the Velo & Lav but don't think it'll do any harm in the BSA..
Just my opinion, hope it helps..

Adrian

[dpaddock]

I've been using 40 grade diesel engine oil in my A10 for a couple of years now. The reason is that diesel oils retain the anti-friction additives that have been removed from gasoline engine oils (those additives reportedly cause early catalytic converter failure in automobiles, and the oils have been reformulated as a result). The cam followers in the A7/A10 engine are non-rotating and need all the slipperiness of those anti-friction additives.
One can certainly add some STP or other friction modifier to non-diesel oils, but I figure that diesel engines are designed for heavy duty and the lubricating oils have to be formulated for that. So far, there are no problems.

David

[nigeldtr]

Hi Alan,

This forum is great, beats watching the tele any day of the week ? how did we cope without forums and internet!

Anyway, I did some tests last summer, gets regularly to over 30C here in central Germany and I found it didn?t make much difference SAE 40 or 50. Once the engine got hot, the viscosity fell through the floor ? oil was at about 80C (I seriously thought about fitting an oil cooler ). These were straight single grade oils ? no additives. They were from a specialist supplier here and he said that a 20/50 should be better, 20 to start with and thickening to 50 when hot. Apparently there are some expanding molecule chains that get excited and thicken things up ? if this is true, to my mind, it?s the perfect solution ? sorry no pun intended. Equally, he said thick oils are fine but move more slowly so you don?t get as much quickly to your bearings to do the lubrication and cooling bit especially important from cold, should get a discussion going

That?s my bit, feel better now.

PS Interesting info about the Diesel oil!

[Goldy]

I don,t think it really matters which oil you use. In the 60,s we just bought the cheapest. The main point is to change it frequently. All the best and welcome.

[bsa-bill]

Goldy - spot on, and there was not a lot of choice either Castrol, Shell, and a few smaller brands THEN came Duckhams 20/50 (green it was) and we should remember it was designed for motorcycles

David I think oil for diesel engines might well be more robust, amongst other considerations -higher compression rates (my last diesel car was 20:1)
but also engine oil for diesels was amongst the first I encountered with detergent, this was in the late fifties

[lawnmowerman]

Interesting point regarding diesel oil. I will be changing the oil in the next few weeks so I may give it a try. What grade diesel oil should I use and should it be straight or multigrade, mineral or synthetic. Also detergent or non-detergent - the PO had the engine rebuilt about 500 miles back by JB engineering so hopefully the sludge trap and all the crud was cleaned out.
A friend of mine swears by diesel oil and uses Caterpillar 10/50 - or was it 10/40.

Jim

[Stu55Flash]

Alan, welcome to the forum. This interesting discussion goes on at various times on various classic tractor and car forums as well!

A key consideration for which oil to choose should be the oil pump. The original pumps where built to work with 30/40 grade oils. Modern multigrades are too thin for the pump to work as intended. Compounded by further restrictions like a paper filter make the situation worse. As discussed modern multgrades have detergents to carry crud to the paper filter so there is no need for a sludge trap in a 'modern' engine. Don't know what the people making modern spec pumps, such as SRM, would recommend.

I am using straight 30 grade for winter changed more regularly than recommended to keep the sludge trap clean for longer.

Stu

[chaterlea25]

HI All,
Some years ago before the "reintroduction" of "classic" straight 30/40/50 oils
It was quite difficult to obtain plain grade oils
I used to be able to get Duckhams fleetol 40 this was used in older diesel engines, then Castrol had 30 and 40 for diesels as well (RX super????)
Nowadays it seems modern diesels use very low viscosity oils and I have not seen a straight diesel lube in the British Isles for a long time!!!
dpaddock can probably still get them in the USA as I believe thyey are available there??

Nigeldtr, I dont think you are correct in your thoughts about multigrade (or we are interpreting things differently??)
Multigrade to the best of my knowledge is described like this,
It has the viscosity of the lower number (say 10,15, 20) at say 0 deg C
And the viscosity of the higher number  (say 40 ,50 ) at say 100 deg C ( I dont have the actual temp figures in my head )
It does not get thicker as the temperature rises!!

I dont claim to know how all this technology actually works
My wife has a modern Mini (BMW) which uses a  0w/40 oil, which is bloody expensive!!!!
this pours almost like water and I dont know how it works??????

I know that SRM will not guarantee their rebuilt engines UNLESS they are run on straight monograde oil

Alan, I would recommend moving the filter to the return line, as others have said

Regards To All
John O R

[scotty]

Alan

Welcome to the forum..sounds like a nice project you have going there.

I've recently plumbed in an external oil filter on my A10 on the return side.
One of a few reasons for the return side location, I'm told, is that the return side of the pump has double the capacity of the feed side.
i should add that the A10 is not yet running but i have the same filter set up on my B33 and it works very well along with same 40 grade diesel oil that i use on the boat.

[Alan @Ncl]

Thanks to all of you who have replied (12 so far, which is fantastic) to the thread that I started (restarted really) on oils and filters.  Its great to have access to such expertise and thanks too for all the warm welcomes. 

A range of opinions is evident, as would be expected on a subject like this.  I was half expecting to get more ?flack? for having a filter on the inlet side!  However, from reading previous posts you are clearly a very courteous and friendly crew so perhaps I should not have worried.  That said, it does seem I am in a minority of one at present in having plumbed it this way in the past, and several of you have gently nudged me to move it onto the other side.  This would be easy enough to do as the way its plumbed all I have to do is cut into and connect the return pipe and then bridge the ends of the feed hose with a bit of 8mm tube (see picture if interested).

I am not going to decide too quickly what to do next and some of your replies have prompted me to do a bit more research on oil specs, viscosity etc. I will report back when I finally decide which route to take.

Meanwhile, can I hark back to earlier posts about exacerbated wetsumping occurring in some cases after fitting a filter in the return line. Can I ask did a consensus ever materialise about how this could happen? 

Linked to this, does anyone know what kind of pressure drop typically occurs across a cartridge filter under normal temperature, viscosity and flowrate conditions?  With a positive displacement gear pump, such as we have here, its hard to see where else the discharge flow can go except back to the tank, up to the rockers or internally back through the pump by leakage (i.e. three potential paths in parallel with oil choosing which way to go based on relative flow resistances between them). 

I suppose that if the rocker take off was plumbed on the inlet side of the filter rather than on the discharge side, then a fairly modest filter back pressure could easily divert more oil back into the engine.  I don?t suppose any of the problem cases quoted were plumbed this way but if they were, perhaps this could explain it?

[A10rocket]

Alan,
another advantage of having the filter on the return is your pumping filterd oil back into the
tank.  Having the filter on the feed means any particals in the oil get pumped into the tank and start
 to settle in there and eventually you end up with sludge in the tank.