Square four pressure problems again

[FletchBurton]

Hi,
I have just rebuilt my four, it has a mk1 bottom end and cast iron barrels and head.
I fitted club con rods, cleaned the sludge trap, oil tank, any oil gallery i could find and fitted a morgo pump. Oil is straight 50.
Turning the bike over in first without plugs with a paddock starter resulted in oil pressure well over 100psi at the gauge. So I removed the pressure relief valve spring (new from Drags) and the ball bearing and left the plug out of the end of the crank. Turning over again, no oil pressure as expected.
Replaced the plug in the crank without the spring and ball bearing, turning over oil pressure again well over 100psi.
So does anyone have any thoughts on what is wrong/causing this excess pressure.
Thanks
Fletch

[simon.holyfield]

The new spring and sae 50 oil. Try using 20w/50, but my engine will generate 75 psi easily.

[FletchBurton]

Yes but I still get over 100psi without the spring

[Pete.Silson]

Replaced the plug in the crank without the spring and ball bearing, turning over oil pressure again well over 100psi.

Fletch,

Repeat the test (with the body fitted but no spring or ball) but don't refit the aluminium cap. If oil comes squirting out of the relief valve when the engine is turned over then the problem is possibly the aluminium cap blocking the exit of the pressure relief valve.

What sort of washer do you have on the cap? It should have a thick copper washer - paper or fibre washers can be too thin. Also the original caps are thinner than some modern pattern replacements and give that tad more space for the oil to exit the end of the relief valve.

Pete

[FletchBurton]

Hi Pete,
It does not have a "cap" or washer it is just a plug, I will try to up load a couple of pics.

[will_curry]

Your relief valve doesn't look anything like the ones I've come across.

In these the ball and spring fit inside the body and are held in with a split pin and the
whole body screws into the end of the crank. When the valve opens the excess oil
escapes through a hole in the end of the valve. It's not obvious to me where the oil
could come out of the arrangement you have and, if the oil can't get out it will behave
exactly as you describe.

Take a look at the Draganfly website for a picture of the body (2151-50 is the part number
I think). Unfortunately it doesn't show the business end.

[FletchBurton]

Hi,
Thanks for the replies.
Has anyone got a picture of the relief valve assembly?
I think after speaking to Mr Longman and looking at the replies what I have got is just a plug.

[nevhunter]

The final plug must let the excess oil out. High pressure risks damage. You can't have the spring being able to go to an "S" shape either. Nev

[Pete.Silson]

Fletch

It looks like you have got an adjuster from an iron 4G relief valve (2156-37) - the one that goes into the timing cover.

For a Mk1 what you need is a relief valve body (2151-50) plus a spring (2154-50), a 3/16" ball bearing and a 1/16" x 5/8" split pin.

I can't really see from your picture but the spring you have might also be the one from the 4G valve (2154-37). This spring is not the same as the one for the Mk1 so it might be wise to get a new spring (2154-50) as well as the body just in case.

You can probably re-use the ball bearing

Pete

[allan.walker]

You'll have to join the queue, unfortunately. Draganfly have the OPRV body on back order.....