Oil pump problem?

[Slemdog]

I have a 76 honda cb750  that has 20K miles and is and has been perfect! But the check oil light has came on and I replaced the oil pressure switch but the light is still on.  The oil level is correct in the motor and I can't imagine that the oil pump would need replaced.  Is is possible that I have an electrical short or some other electrical issue, or do I have a mechanical problem?  HELP!!!

[TOOLS1]

If it has not seized up, then the oil pump must still be working. It is possible to have a short. The way the circuit works is that the juice goes to the light, then it goes to the switch. The switch grounds the connection until the oil pressure breaks the connection. I would disconnect the wire from the switch. If the light is still on, then, you have a short.
TOOLS  

[Slemdog]

Thanks for the tip.  The bike runs great still, but I am afraid to damage it.  I will try disconnecting the switch.  Thanks!!!!

[Peterwh]

I suppose there's an outside chance you could have low oil pressure!

[Slemdog]

I hear ya! I dropped the bottom sump cover and made sure that the pick up screen was clear of any debris.  It looked ok, if I don't have a short in the system, I'll try a new oil pump.

[sgtslag]

Try connecting an oil pressure gauge, in place of the OEM pressure switch.  It is the only way to be certain that you do not have a blockage, with good oil pressure, and flow.  Maximum oil pressure is 72 PSI @ 7k RPM.  You do not need to rev it up to 7k, and you should not, unless you are riding, or you will damage the engine.

There are many oil channels within the block.  It would be a good idea to treat the engine with SeaFoam, to ensure good flow throughout the engine, and the transmission.  SeaFoam will dissolve carbon deposits, varnish, and other crud, within the engine, and the transmission.  Follow the directions on the can.  It doesn't take long to clean everything:  put it on the centerstand, add the correct amount of SeaFoam to the crankcase, then let it idle, shifting through all gears, letting the rear wheel spin freely, to ensure proper circulation through the transmission, and the engine.  Then drain the oil, and change the filter.

Above all, check the pressure!  Cheers!

[LukeM]

I'm thinking one could put a tee fitting in place of the idiot light oil pressure sensor, and run a actual oil pressure gauge at the same time.  I've seen a few pix of people who put the gauge down where the engine is, but maybe an electric gauge near the cluster would be more useful. The rationale is, maybe you can see a drop in oil pressure on the gauge before the idiot light signals there's a problem.  Might save all kinds of pricey engine bits in the long run.

What is the consensus on the sound an engine makes when the oil pressure is low?
Luke M

[TOOLS1]

BANG! clunk, clunk, clunk, clunk.
TOOLS

[sgtslag]

By the time it becomes audible, damage is likely occurring already.  Better to stay ahead of the low pressure.

You are correct, a T-connector is feasible, and an automotive pressure gauge is workable.  I would compare the mechanical, Bourdain Tube gauges, alongside of the electric:  they sometimes are more granular, and accurate, depending upon needle deflection [electric gauges usually only have a 60-degree range, while many of the mechanical gauges have 270-degree deflections, which means far greater accuracy (spec. at 3-5%, officially); they are sometimes less money, as well].  Only concerns with mechanical gauges is the tube:  can't knick it, kink it, or twist it (but you can make large loops of excess tubing) -- will destroy the entire setup.  Cheers!