Oil pressure

[zidz]

Hi guys,

need an advice again

I took my A50 for first miles and I have a problem with oil pressure.
When it is cold there is pressure around 60 psi. As it comes hotter, pressure is going down and when it is really hot it is around 20 PSI in normal revs. I can't get over 30 PSI if I really rev it and on idle I going nearly to 0 - warning light is on on idle.
If I little bit increase revs it goes off again...

If I check returning oil - I can see nice flow when cold but is it is hot it seem more like spitting of oil even if I rev it....


Oil pump and OPR has been cleaned and I checked timing side and there was no play.
I use oil Castrol 20W50

https://www.ebay.com/itm/296399983200?itmmeta=01HWPMM3QAJKQMD5RAJTS9TYND&hash=item4502d0d260:g:uGEAAOSw0hxmMG~r&itmprp=enc%3AAQAJAAAA4D%2BLvkcuFsdHZcCNsh8%2FG7jqLNVJ674gMcvYEfaBOAgXJ5NIL3hzFiG5TWbai2PbpLlcJq6beEwcNUIPRuR31sOspIohKSg6012xfxojolB6P7jHxRuJ7NNSxAxgz9V8NKITyGzjRvgZWny0Uec1yq35x5yAnBj%2BYdfqK9zd5JBKj75F7k0OyJOg5clf1GDiCan0ejK2cvGMOx8LcCFUPVAX8aH%2FjQQFepAChyo5dGYfYKJHqsSMfQ9jU3bg3OVlcRF%2FW6bO1LS7Li0yn7YzUHgccD0tuFGUIa2ISUMXKBQB%7Ctkp%3ABk9SR-C70NTlYw


I have mounted oil pressure gauge on handlebars and I would like to ask you if hose diameter and length could affected oil pressure (inner diameter is 5 - 6 mm, length could be 80 - 100 cm)?
Which oil do you use?

I will try to fit new spring to OPR - I have still mounted original OPR (flat one).
As last step I consider to order SRM pump and OPR but I would be glad if someone could give me an advice what check else...

Thank you
Zdenek

[DAVE BRADY]

Good morning Zidz,

A starting pressure of 60psi is normal as the oil is cold and the pressure release valve is opening at 60psi to release the pressure.  As the oil warms up the pressure will drop and the pressure release valve will not need to open.
When cold there could be bit of oil accumulated in the sump and as it is returned it will give a constant flow until this oil is cleared.  Once warm and the pump is doing its job it will scavenge quicker than the oil gets pumped through the engine so will tend to spit rather than flow.
The down side of an oil pressure gauge is that you will see the oil pressure drop as the engine gets hotter and this can be disconcerting but as rule of thumb you should get 10psi per 1000rpm with the engine warm.  So at 2000rpm pressure of 20psi etc.  There will come a point when the centrifugal force generated by the spinning crank will in effect suck oil through the crank and you would see a pressure drop.  I have seen this at 70+ mph and after slowing down the pressure comes back to the 10psi:1000rpm.
The oil light is set to come on if pressure drops below 7psi.  BSA must have considered this to be a minimum pressure at tick over and I consider this to be a crucial  indicator.  It is possible that in your engine the pressure at tick over is a bit too low even though you have no detectable play in the timing side bush.
many of us tack great pride in being able to set a slow and steady tick over but it is not a good idea to leaver a bike idling at 700 rpm when to oil pressure will be quite low.  I used to do this but now would rather have a slightly faster tick over for better oil feed to the engine.
There is also the possibility that your pressure switch is a bit off so why not very carefully sped up the tick over until the light stays off and consider dumping the pressure gauge.

Dave.

[zidz]

Hi Dave,

many thanks for your answer.
Unfortunately I don't have RPM gauge, but from ride I don't think that I pass 10 psi:1000 rpm. My estimation is that on 4000 rpm I have 30 psi and it is maximum I can get when engine is hot.....

Could be pressure affected by larger hose for oil pressure gauge?
Do you have experiences with SRM pumps?

Thank you
Zdenek

[DAVE BRADY]

Hi,

The size of the pipe to the gauge may affect it so try and fit the correct size if possible.  The SRM pumps are very good and are supposed to be fully tested before being sold.  Before gong down this route try the gauge pipe.  What year is you bike as the last pumps to be fitted by BSA were quite good?

Dave.

[zidz]

It is 1969...
What size of hose do you recommend?
As I said at the moment I have 5 - 6 mm inner diameter, but as I could see on pictures there are used 2 - 3 mm sizes....

I will try cut the hose to 20 cm or something like that. At the moment I have gauge on handlebars so maybe that could be the problem in combination with larger diameter...
I will probably change spring in OPR too....

[Allan G]

Pressure is pressure, it doesn't matter what size the hose is. The bigger the hose, the longer it takes to fill, though once the engine is running and it's full the amount of pressure on the gauge is the same regardless of the tube size.

Flow on the other hand is effected by size.

If you tell us what speed your doing and in what gear your in. We can work out roughly what rpms you're doing.

If you know what gearing your bike has then we can quite accurate.

[DAVE BRADY]

Hi,

I would think that most car parts suppliers will have the proper tube for the gauge in stock.  The length is less important as the proper tube does not expand with the pressure.  Make it short enough to be tidy but long enough not to pull or snag when the handle bars are fully turned in either direction.
The spring in the OPR is probably ok as it released at 60 psi and as your bike is a '69 it should have a good pump prior to the last ones in cast iron although it could be a bit worn.
Increase the tick over a bit to keep the light out.  It is also possible that the pressure switch needs replacing.

Dave

[zidz]

Hi Dave,

pressure switch has been changed and from my point of view works properly (according to gauge reading).
So you mean that pressure around 20 psi at 3000 rpm is acceptable?

I will short the pipe to gauge as much as possible only for test and will se the difference...
Which oil do you use in your machines?


@Allan - I will do some readings in afternoon and will let you know



Zdenek

[rhyatt]

I don't know what oil grade the factory used/recommended in their handbooks , but if a monograde eg sae 40 or 50 , then that is worth a try.
Yes, I know a 20-50 is meant to give the body of 50 when hot.
At the end of the day, these bikes were built to their specs and cars with shell bearings of that era ran 30 to 40 psi at 3000 rpm hot.

[DAVE BRADY]

Hi,

I think 20 psi is a bit low for 3000 rpm.
I use a full detergent 20/50 and have full flow filter fitted in the return line.  Both my A65 and my wife's A10 have covered big mileage and before these bikes I ran an A10 with sidecar for many miles on 20/50 as well.

Going by the book, '69/'70 models, is quite interesting and the oils recommended vary quite a bit but from 20 sae to 50 sae.  It seems to depend in what country the bike is in and what brand is used as well as season.
Whilst the oils for the UK seem to be mono grades some for 'other countries' are multigrades of varying grades.  For weather temperatures  from 0º to 36º one of the recommendations is Esso 20/40.  Did the recommendation change for '71/'72 models?

Dave.

[LightningAndStarfire]

Sometimes there can be leaking threads between the case and oil pressure valve. Oil passes the threads into the sump which indeed gives lower oil pressure. Can be difficult to remedy but careful use of sealant or PFTE plummers tape can help. Beware of the stuff coming into the oilways of course!

I doubt you will notice any difference by shortening the tube to the gauge.

Cheers
Thomas

[john sever]

Hi  I've just been down this road with my '69 A65L. A new OPRV and heavier oil didnt help (10PSI when hot), so finally bit the bullet and pulled out the oil pump. It was a cast iron one (which are supposed to be the better type) but the spindle had side play of 2 to 3mm, so totally stuffed (there a good utube on this by Paul Henshaw). I was lucky enough to pick up a good 2nd hand pump (monkey metal, not cast iron) for a good price and now have around 40 to 50 PSI when hot. If all else fails, watch the utube and pull the oil pump.

[zidz]

Hi,

Bike after 15 kilometers:
https://www.youtube.com/watch?v=IUiqsiha-Xc&list=PLS-3yIg2iyRIYj7jDVytPn2ne7Al9vOe4&index=17

And another 5 km when I get warning light when idling:
https://www.youtube.com/watch?v=izfa9wGPI5w&list=PLS-3yIg2iyRIYj7jDVytPn2ne7Al9vOe4&index=16

I have 20T sprocket and following meassures:
3rd gear 60 km/h - ~18 PSI
3rd gear 70 km/h - ~23 PSI

2nd gear 50 km/h - 20 PSI


I am decided to bite the bullet and switch to SRM pump to have piece in mind

Zdenek

[john sever]

Hi
I'm happy to give you my old one, however they are pretty heavy and I'm in Australia, so postage could be a bit. I can weigh it and tell the postage from here to wherever you are if you like.
John

[Allan G]

Hi,

Bike after 15 kilometers:
https://www.youtube.com/watch?v=IUiqsiha-Xc&list=PLS-3yIg2iyRIYj7jDVytPn2ne7Al9vOe4&index=17

And another 5 km when I get warning light when idling:
https://www.youtube.com/watch?v=izfa9wGPI5w&list=PLS-3yIg2iyRIYj7jDVytPn2ne7Al9vOe4&index=16

I have 20T sprocket and following meassures:
3rd gear 60 km/h - ~18 PSI
3rd gear 70 km/h - ~23 PSI

2nd gear 50 km/h - 20 PSI


I am decided to bite the bullet and switch to SRM pump to have piece in mind

Zdenek

Get the LF Harris oprv, the srm unit will eventually stick open and you'll see the same issues you are now.

You're running one heck of a big sprocket on an A50 if it's 20t. You want to be running ideally an 18t sprocket. The bike likes to rev, an A50 hasn't the guts to pull such tall gearing and you will damage the motor, which is probably what is happening already.

Listening to the video there is an inconsistent whine hidden by the lovely exhaust note. But it's there. Something is either tight and/or being starved of oil.