Engine Oil Choices for a Z1

sdinse wrote:

First a bit of background.  I just completed replacing the head gasket and most of the cover and oil pan gaskets to stop the leaks I've been having on my 73 Z1.  As long as the oil pan gasket was off, it was a good time to check the oil pump.  The screen was a bit clogged with what I would think is a bit of clutch material, not so unusual, so remove the oil pump, disassemble, clean, inspect and put back together.  Upon opening the pump, the gasket came apart in several pieces, some of which had to be scraped to remove, so consequently I needed a new gasket.  The gears and clearances seemed to be in good shape and within spec, at least for side clearance.  I did not measure the end clearance since I didn't have any Plastigage handy.  When the new standard sized gasket arrived, it seemed a bit thicker than the original, but then, the original had been compressed, so in went the new gasket and the oil pump was reinstalled.  This engine has never had a problem with low oil pressure but now I'm seeing the oil light come on at anything below 1500 rpm when hot.  Does anyone know what the switching pressure is for the oil pressure switch?

So, here's the question:  I filled the engine with Shell Advance AX5 20W-50 Motorcycle Oil( rb.gy/p1sgim ), could this be the problem?  It did seem a bit runny for a 20-50.  I'm thinking perhaps I should switch to a Kawasaki brand oil, but which one?  The K-Tech SAE 20W-50 4-Cycle Engine Oil( rb.gy/eej8ji ) touts "Protects against excessive viscosity decrease at high temperatures", which seems to be my exact problem at the moment.  Or would the KPO Conventional 4-Stroke Engine Oil( rb.gy/efv20u ) or the 4-Stroke Motorcycle Engine Oil 20W50( rb.gy/b4izgu ) be better or maybe even worse.  I'm thinking that any one of these should be an improvement but would like to hear of any knowledge or experiences to determine which would be the best choice.

This is my first step in diagnosing this problem, which is the easiest thing to do before tearing back into the engine.  Pressure testing cold is about 2 psi at 3000 rpm, a bit on the low side, but is it the oil or the pump?  Now I wish I'd never opened up my working oil pump. 

  A clear case of "If it ain't broke . . ."

  

hardrockminer wrote:

My father was an airforce mechanic in WW2.  His initial training consisted of filing a block of steel until the opposite sides were parallel to within 1/1,000 of an inch.  He also said the reason they did that was because the heads on Merlin Spitfire engines were hand fitted to the cylinder blocks without gaskets.  

The oil pump runs in the sump and I wonder if it can be run successfully without a gasket?  Leakage would simply go back to the sump.  The only issue might be too tight side clearance.

hardrockminer wrote:

The oil pump runs in the sump and I wonder if it can be run successfully without a gasket?  Leakage would simply go back to the sump.  The only issue might be too tight side clearance.