Filter in Oil Feed Line

[nigeldtr]

Hello Everyone,

John, thanks for the oil info. I thought the idea of a multigarde was to be thin when cold and a bit thicker when hot. I may well be wrong, far too much chemistry or what ever it is for me.

PS I also fitted the filter in the return line on my plunger, tucks in nicely behind the gearbox.

Once the engine is run in, is it worth popping in a bit of molyslip or what ever its called?

Re the wet sumping, I think it?s probably more likely to be a worn oil pump or in the case of my SW A10, the pump was not seated correctly on the crankcase!

Regards

Nigel

[Triton Thrasher]

I thought the idea of a multigarde was to be thin when cold and a bit thicker when hot.
Nigel

Not exactly.  It thins out when hot, but not as much as a non-multigrade.

20W/50 is supposed to be as thin as a cold mono 20 when cold (W for winter).  It's as thick as a hot mono 50 when hot.  Hot 50 is thinner than cold 20.

[iansoady]

Once you start an oil thread it never stops....

I found this the best guide I've seen - from someone who spent his working life in the oil industry and rode a Commando till his unfortunate early demise.

[Alan @Ncl]

I was going to offer some comments based on the recent reading I have been doing around the viscosity issue but I think Triton-Thrasher sums it up admirably.  Also Iansoady reference article is excellent.  Its easy to see how people can get 'the wrong end of the stick' and I have certainly learned a lot these last few days.

I am now beginning to wonder what advantage monogrades could ever have relative to a multigrade that has the same upper SAE number?  At face value, it seems that with monos, we are always potentially in jeopardy during that critical cold start up period?  So why do respected authorities like SRM like us to use monos in their rebuilt engines?  There must be some arguments in its favour?

[nigeldtr]

Triton Thrasher,

I read something like this but you put it much more clearly!  It doesn't get thicker, but also not thinner than the 50W correct ????

I will stick to the 20W/50W for now.

Nigel

[trevinoz]

I have said this before and will say it again.
The oil recommended in the 50s was what was available.
In the 60s when multigrade oil became widely available the bike manufacturers changed their recommendation to that product. Just have a look at the late model hand books.
The engines are essentially the same as formerly just prettied up in new cases.
They also recommended EP oils for the gearboxes which opens another can of worms.
Trev.

[Triton Thrasher]

Triton Thrasher,

I read something like this but you put it much more clearly!  It doesn't get thicker, but also not thinner than the 50W correct ????

I will stick to the 20W/50W for now.

Nigel

You have to be sceptical of proud makers' claims.  I wouldn't be surprised if hot 20W/50 is actually a bit thinner than hot 50. It may even be a bit thicker than cold monograde 20, when cold. 

My experience is with Triumphs and I say with confidence that monograde 50 is too thick when cold, to be used in Triumph twins on cold mornings in Scotland (and all mornings are cold here). Oil pressure can collapse when you rev up.  20W/50 works fine.  I've never used monograde 40 or 30, never owned a BSA Twin and do not know why SRM doesn't like multigrades.

[Stu55Flash]

The article on multigrade oil is fantastic but it considers the oil only not the rest of the engine. The oil technology undoubtedly  moved on but so did the engineering within the engine. This went hand in hand through the 60 and 70s. The technology developed in  iteration, I don't think you can consider any one of these in isolation to the other. The article considers the oil what about the rest of the bike engine?

Stu

[Butch (cb)]

Do love a good oil thread.

Putting viscosities aside for a moment. My thoughts were that the monogrades were at least designed to dump the particles, and hence we have a sludge trap to collect them. The 20/50 would carry the particles around, hence you would plump for this if you'd fitted an in line filter. That of course is ignoring comments previously posted here on which of these might now carry detergents and the like.

On the viscosity front, using the 20/50 is going to exacerbate any wet sumping problems there might be of course.

We were talking on issues of preventing wet sumping quite recently somewhere here. Of my experiences:

My engine was fully rebuilt and came loaded, I think, with a monograde. I subsequently fitted a paper filter in the return line. (Fitted in the tool box btw, as the fitting instructions suggested, but which I understand might in fact be higher than is thought good here). At the same time I switched to a 20/50. The bike wet sumped horribly. I fitted an SRM bottom plate with sump plug, but as the crankcase would fill in just a couple of days I tired of the constant draining I had to do from that. So I fitted a Britie valve in the feed line. No more wet sumping.

However in pretty short order I seized the motor on the timing side crank bush. Roger at Cake Street pulled it down and rebuilt it this time. His verdict - the crank was a little tight in the bush, the oil pump body was shot. Maybe. My thoughts are that perhaps the oil pump was poor enough that the oil drained through it from the one way valve down and then the pump didn't self prime.

Either ways. The bike is now fully oil tight and doesn't wet sump a jot - this with that valve no longer in the oil line. Not sure what oil Roger has used - but I'll be checking with him.

[olev]

Gday,
I've got one of Goffys oil filters and intend to fit it to the plunger A7.
Can anyone tell me the most elegant spot to fit the dirty great thing.
It won't go in the toolbox.
Nigel said he fitted his behind the gearbox and that seems like the go.
Photos and ideas about rooting the plumbing would be appreciated.
cheers.

[alanp]

This jogged my memory re 20W-50 oils and wet sumping. I've got a filter fitted on my return line and use 20W-50 oil and since November when she was kept in the unheated garage it has wet sumped 1 1/2 litres of oil and that's with a new SRM pump. That's approx 20 ml per day. Guess that's the 20W telling me it's thinner in these conditions than 50 grade and will sneak through.
This means that during the riding season with at least one run a week it's of no consequence and I haven't ever noticed any problems with starting or running, so I can't see me bothering to fit an anti-sumping valve, unless I get too bored waiting for the better weather that is!
Regular bike users are probably worrying unduly over this.
Talking about waiting for the better weather, a friend of mine couldn't wait and ended up trashing his gorgeous Dunstall BSA A65 on the black ice/frost down the end of his road last week. Patience my friends!

[trevinoz]

Stu,
         Your statement that engine technology advanced throughout the '60s and 70's doesn't apply to British motorcycles.
They were still 30s and 40s designs!
Trev.

[Alan @Ncl]

Just taking stock so far, it seems the monograde/multigrade debate can be crudely summarised as follows.

Ideally, oils would have constant viscosity (thickness) independent of temperature.  So on a graph of viscosity against temperature an ideal oil might appear as a horizontal line as shown below.

However, in practice, viscosity does not stay constant.  It decreases (exponentially) as temperature increase and this is true for all oils.  So if we draw a graph of viscosity (on a logarithmic scale) against temperature, we get something like the sloping lines shown on the diagram below (not drawn to scale though as this is for illustration only). 

For a monograde oil such as SAE40 we get a steepish straight line sloping down from left to right. Note this line intersects the one depicting the ideal oil at approximately the operating temperature for which it is designed (say 100 C).  The problem is that at low temperatures, this oil will be very thick so drag will be excessive and lubrication at cold start may be poor.

One answer is to use additives to help flatten the viscosity line (i.e. reduce its slope or increase its viscosity index) so that it lies nearer to the ideal horizontal line. Hence at lower temperatures the oil behaves more like an SAE10 whilst at high temperatures, continuing to behave like an SAE40.  This is basically what multigrade oils do.  Hence they have titles like SAE 10W40 to designate that they behave more like a 10W grade when cold in winter but revert to SAE40 at normal operating temperature. 

The potential advantages of multigrades are thereby evident, especially during starting and at low temperatures.  So what, if any, alternative advantage can monogrades potentially offer? I have seen it stated that:
1   They do not deteriorate (thin out excessively over time at higher temperatures) to the same extent as the multis do.
2   Monogrades are less prone to sludging since they do not contain the VI additives. 
3   They are less prone to wetsumping (important within our current context).

This makes sense to me and fills in a bit of background.  Unfortunately, it still does not definitively tell us which is best!  Perhaps the relative advantages cancel each other out so that, as some on this forum have said, it does not really matter which we use, as long as we change the oil regularly. 

[nigeldtr]

Hello Olev,

please see attached pictures. The bracket is mounted to the top rear engine bolt and between the oil tank bottom fixing and frame. You need to drop a vertical plate down from this plate to mount the filter head witch is roughly 2 cm offset behind the seen horizontal mounting plate. It fits in well and you can get your hand in to do it up without any great problems, The only difficult bit was bending the tight radius on the copper pipe in the return to the tank. The next filter, I will spray black

If you need more pictures let me know.

Nigel

[nigeldtr]

Other picture