Have had my 1991 project since last December and since getting the engine going and warmed up, at tick over the the oil pressure light comes on. Have just changed the oil and filter with 20/50. Light came on before oil change and still comes on now. Soon as you rev the engine off tick over the light goes out. Anyone had this problem before as only at tick over thought may be a dicky pressure switch.

 

bad switch, broken oil pump chain (unlikely)

 

20/50 may be to thick. Thicker is not always better at times. You need oil that will pass thru the oil passageways or the pump pushes it up against the restriction and you would get a pressure drop down stream. If you are cold starting the bike in winter conditions, the oil will act like 50 weight, to thick. 10W-30 will act like 30 weight when cold and thin to 10 weight at operating temp. That's a huge difference between the 50 cold and 10 weight operating temp.

Oil pressure is based on how much volume and pressure the pump puts out and is governed by how easy it passes the engines restrictions. If the mains and connecting bearings are shot (larger gap) oil is lost and pressure drops. Loose cam clearance also causes pressure drop.

You may have one of the above conditions. Trying thinner oil would be the easiest thing to try first.

I always use 10W-30. If I do an oil change when I expect my cooling fan to come on often I may go to a 10W-40 but I never go to 20 weight because it gets cold here.

 

what's your "tick over" / idle rpm set to ?

 

Thanks for replies yes idle speed is set to 1050rpm. As said when starting up on old oil and new oil getting same symptoms, no light when cold but warmed up and fan has been on the oil light is on on idle. Blip throttle goes out immediately, will look at wiring to pressure switch first might be bad connection, then will take out switch. Have an oil pressure gauge with a double connection bolt to engine case so can run both pressure switch and gauge. Will have a look tomorrow as busy today. Looked in manual does not say what oil pressure is at idle anyone know, thanks