sq 4 oil pressure....

[bob cottam]

Hi all, clocked 130miles now on re-built mk2 square four, all is really well, but when fully warm, oil pressure drops to about 10 psi. I am running Castrol XL20/50 oil.
I note from Waller, that the mk2 oil pressure is not that high in any case, its given as 23-35psi.

I have a Morgo pump and a cam oiler kit fitted, (without the supplied restrictor rod).
According to Morgo, their pump relief valve dumps at 55psi.
When stone cold, according to the Smiths gauge on my handlebars my motor develops 45psi, this reading is taken from the top end of the rocker supply line, apparently, the oil pressure here is a little lower than at the crank .
All this assumes my gauge is accurate of course, but it seems to work OK.
10 psi when hot at tickover-rising to perhaps 20 psi at revs. is a bit low for me. I know the cam oiler robs some pressure.

What sort of pressure figures would be normal for a MK2 in good fettle?

[dave.owen]

Similar to what I'm getting.

Just back from 40mile ride.. Checked oil temperature 86 deg C
Dave

[Bob.Murphy]

I used to run my MkII on Castrol Grand Prix - Straight 50.

It was difficult to start on a frosty morning but was plenty thin enough with the motor warm.

It used to run at 52 psi on the road but tick-over when hot was only about 10 - 15psi from memory.

I suspect a 20/50 multigrade is a bit thin for a large air-cooled motor. I run the 'VH' on straight 50 as well.

Bob.

[simon.holyfield]

I use Penrite 25W/70 in my Mk1. 75 psi cold, independent of engine speed; 55 psi hot running; 25 psi hot idle.

[nevhunter]

The only reliable oil pressure indication would come from the oil galleries near the pump or mainbearings. (not easy). Once you tap off something like the supply to the rockers you are losing accuracy. 80 -90 C is a good temp for the oil as any less may result in some water staying in it, which is often the cause of premature failure of the ball races in the engines of our infrequently used bikes.
In the absence of anything special I use Aero engine oil W-100 Plus or 20-50 in a cold climate. which is for aircooled engines and the PLUS is for corrosion protection of the innards. I don't get any scuffing on the VH cams either which can happen if the oil hasn't enough "guts" Most cars use roller followers these days and the cams are not a critical lube part and also the additives are not welcome in the environment or the CAT converter of a modern vehicle so some oils just don't have the antiscuffing qualities you need. Some of these AUTO oils are not good for the gearbox either for the same reason. Nev

[brenton.roy]

Hi Bob, I will wait for an expert, but think one issue is that the spring in the relief valve loses strength.
Changing it for something a bit heavier should raise both upper and lower pressures.
The oil arguments have all been had and 20/50 is commonly used.

[david.anderson]

Bob
I initially fitted my mk2 with a 100psi gauge with the Morgo. That gauge showed a constant 50psi oil pressure at idle or speed. That gauge died so I fitted a 60psi gauge. It goes off the scale when the bike is first started but then comes back to show about 40psi with a hot idle or 50-55psi at speed.
My gauge is tapped into the rocker line so that would be similar to yours. However I do not have the cam oiler so that probably accounts for the difference in idle oil pressure.
With the original oil pump (fitted with the drags steel body) which I fitted prior to the Morgo, a hot idle did not register any pressure and oil pressure only rose to 40 psi at about 60mph. So I would not worry about your oil pressure but would be suspicious of the accuracy of the gauge.
When it comes to oil choice it is Mobil 1 V twin for me. It takes the heat of the 4 in our hot summers.
David

[bob cottam]

AHA!! Found it!- my missing oil pressure was there all along....

I decided to investigate my seemingly poor oil pressure a little further. My existing pressure gauge is tapped into the rocker line at the far end, where it feeds the rockers. I was suspecting the cam oiler kit to be bleeding off a lot of pressure and was considering fitting the kit supplied restrictor pin . Turns out no need at all- I made a double length oil feed stud to screw into the crankcase, enabling me to fit a second banjo in tandem and feed a second oil pressure gauge from the crankcase end of the rocker line, i.e. before the cam oiler take off and rocker feed demand. The second gauge being fed a better indication of true crank/mains pressure.
Those more knowledgeable than me had said that there would be a higher (more realistic) reading here and I was amazed at the difference.
The pressure at the crankcase take off being more or less double the pressure at the far end of the rocker feed. I bought two identical gauges, and checked their readings with air on a common manifold to ensure they were reading the same- they were bang on so I fitted both to the engine and fired her up. Cold crank pressure 65psi (rocker feed 40-45) hot crank pressure 20-30psi (rocker feed 10/15).
I feel much better now..... The Morgo pump obviously provides copious pressure/ flow even with cam oiler in unrestricted format. Only issue so far is a sudden bout of wet sumping....??- did not do it for 1st 300 miles, but suddenly has started.... any ideas?
Bob C.

[Paul_Linden]

Bob, my mark 2 started wet sumping a few hundred miles after fitting a Morgo. I spoke with Morgo tech dept who said it is probably a bit of gasket or sealant caught in the pump, not an unreasonable assumption after an engine rebuild. After a few hundred miles more it cleared up.

[bob cottam]

Thanks Paul, I took the sump plug out yesterday as I could see from the oil tank level that it had wet sumped. I drained the crankcase out completely and about 350cc oil came out. I placed a clean container under the sump overnight,but only a little more came out, perhaps 20cc. I have watched all today and virtually nothing dripping at all now.... Maybe its cured , or maybe its just the colder thicker oil... It will be interesting after next ride to see if the hot oil gets past the valve! Bob.