Low oil pressure at high temps?

[JustcallmeMrT]

Hi all,

I've finally passed my mod 2 and have been taking my bike (1977 CB550F2) to work and back for the last 2 days.  Mornings all is fine, but in afternoon traffic the oil pressure light comes on as the bike starts to get hot.  It has sufficient oil, and I popped the tappet inspection caps and all seems oily up top, so not sure what's going on.  Any suggestions?

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[hairygit]

Does the light go out again above tickover/idle speed? If so, it is not unusual on a high mileage engine, also if it has new rings and shells it will run hot until properly run in. If the oil light comes on much above idle, STOP the engine and investigate further. Well done on getting your licence.

[Trigger]

Hairy is on the right line here. Because you are running new rings, the engine will be running hotter than normal. But, sitting in traffic is not a good way to run a top end in. Have had this problem with 500's and 550's, it was the oil pressure switch.
Have you done a oil pressure test ?
Keep an eye on it

[JustcallmeMrT]

Does the light go out again above tickover/idle speed? If so, it is not unusual on a high mileage engine, also if it has new rings and shells it will run hot until properly run in. If the oil light comes on much above idle, STOP the engine and investigate further. Well done on getting your licence.

Thanks Hairy.  The light doesn't go out above idle, bit does go out after the bike cools a bit.

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[JustcallmeMrT]

Hairy is on the right line here. Because you are running new rings, the engine will be running hotter than normal. But, sitting in traffic is not a good way to run a top end in. Have had this problem with 500's and 550's, it was the oil pressure switch.
Have you done a oil pressure test ?
Keep an eye on it

How do I check oil pressure?

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[Bryanj]

Easiest test is substitute the switch which is on the oil pump, or you can put an adaptor in there to actually check the pressure, but you cant put the cover back on with a pipe connected instead of the switch. Don't put a car switch in there as they work at a different pressure

[JustcallmeMrT]

Easiest test is substitute the switch which is on the oil pump, or you can put an adaptor in there to actually check the pressure, but you cant put the cover back on with a pipe connected instead of the switch. Don't put a car switch in there as they work at a different pressure

Any suggestions for where to get a switch?  Is it a generic unit or do I need a Honda part?

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[TonUp]

I had the same problem with my CB550F2, got a new oil pressure sensor from David Silver. Fixed the problem. It was about £20 I think.

[flatfour]

It might not be the correct thing to do, but as this always happened to my Benelli 750/6 when hot I talked to members of the owner's club and a recognised expert on type and was told to always use 20/50 oil as soon as winter was over. The problem has never returned and very many miles have been covered since.

I now change to 20/50 for the Honda's at around Easter each year, although I have never had the oil light illuminate on them with the engine running it certainly doesn't seem to have done any harm.

In the 1970's, all of my bikes were run on Duckhams Q20/50 throughout my ownership without any mechanical issues arising.