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As part of a long running saga where the oil pressure light came on from time to time on my 501 New York I ended up first swapping the oil pressure switch twice and then doing a bunch of other things to try and make sense of what was happening and whether my engine was stressed and losing oil pressure somehow.

I've bought a 0 to 100 psi analogue oil pressure switch which has an 1/8 NPT thread (a very very fine thread) and an adapter (M12 x 1.5mm).

• 1/8 NPT FEMALE to M12x1.5 METRIC MALE Oil Fuel Pressure Sensor Pump Adapter, bought from https://www.ebay.co.uk/str/hosefittingsuk

• 40mm Liquid Filled gauge, 0-100psi scale, 0-7bar scale, 5ft Nylon gauge line, Universal 1/8npt adaptor, bought from https://www.ebay.co.uk/str/mattlewisracingltd

I ran the electric start with the kill switch on until I saw pressure readings, then started the bike as normal. The reading from cold at idle speed is around 58 psi. As the engine warmed and as I reved the engine in neutral the reading varied from roughly 50 to 70 psi. On the New York (and Excalibur presumably) the left footrest mount clashes with the oil pressure pipe, so I've got the footrest bracket unbolted and loose during these measurements. This means a road test isn't practical until/unless I adapt the footrest bracket somehow.

I'll add more info to this as and when I have it.
PS: These measurements may apply to any of the air-cooled V twin engines.

Julian,

Worn crankshaft bearings can cause low oil pressure. Have you had the clutch casing off? The little rubbery (green or black) tube on the end of the crank is also very important...

Mike

Mike, thanks for the tip. AFAIK the oil seal should be fine, but it'll be worth investigating again if I find the oil pressure drops when I ride the bike with hot engine oil.

FYI the engine was rebuilt by Benjy and I've ridden it for about 3000 miles post rebuild. He replaced the crankshaft, the mains, the big ends, and the oil pump, as this engine was badly seized when the oil pump failed (this aspect of the story is in ATG 372).

The oil light started coming on after about 500 miles post rebuild when the oil level was low because of a weep from the main engine crankcase breather and old O rings on the dipstick. Since then Benjy, Tom Farrow, and I have been comparing notes and ideas on what might be causing the oil pressure light to come on.

I've just ordered some adapters which may enable me to ride the bike with the oil pressure gauge and with the footrest, etc. refitted. I'll hope to post an update within a week, assuming the adapters arrive by Wednesday/Thursday.

The oil pressure lights tend to come on in single digit PSI, not useful. A gauge is much better. I had to replace my sender, I bought a Lucas replacement.

Glad the crankshaft has been reground, one less thing to worry about. What oil are you using? It has been exceedingly hot recently, maybe the 10/40 is too thin? In the good old days (has there ever been such a thing, or have I got rose-tinted testicles?) I used GTX 20/50 mineral oil. But then, the earlier Morinis did not have an oil pressure light... ah, the ignorance of youth

I have had the oil pressure switch fail a few times on my Sport. The Coguaro seems not to have one, there is a blanking plug where the sender ought to be. In the warning light array there is a light for oil pressure and a charge light. Neither are connected. Me no likey.
John