Topic: Low oil pressure when hot? 750k5

[1974cb550k]

So here is the deets. New rebuild top end only. Oil pressure gauge from some honda chopper site, lquid filled. When hot it dropped to 8 psi at 3000 rpm It was 90+ here today. Let the bike sit and cool. Remove tappets and it has plenty of oil at top end, Looked in oil tank and plenty of oil returning. And gauge showed 40 psi at idle while cold. Im thinking faulty gauge when hot but i am going to swap gauges tommrow to test. Any thoughts? Thanks Why would oil pressure drop when hot but be fine at start up. New oil pump o-rings and the one at the shifter as per hondaman fyi. And new oil. when cold 50 psi at 2500 rpm. And what psi should the oil light come on at?

[MCRider]

The light works at 7.5psi.

More pressure at cold when oil is thick.

Gauge measures pressure at the main and conrod bearings. How many miles on engine?

Top end may get oil fine while mainbearings may be too loose to hold pressure.

Or it could be the gauge.

[CB750F2]

+1 with MCRider. Additionally, are you sure that you re-installed the two restrictors and the four little "o" rings under the cam towers? If these are left out you may be getting excessive oil at the top end at the expense of oil to the bottom end. Just a thought. Pat

[1974cb550k]

Mileage unknown. I did not touch bottom end but re-installed the top end as per hondamans book and was VERY slow and cautious when performing re-install. im gonna take it for a rip and then install the other gauge and see if it changes. Thanx

[stueveone]

How was the rest of your testing? Did you get the other gauge swapped out?
Interested to find out...

[70CB750]

What oil weight are you running?