Low Oil Pressure on Honda '78 CB750F SS

[xxthegonzxx]

What's the average oil pressure on these SOHC 4's? As of now I'm getting anywhere from 5-10 PSI at idle, after the engine is warmed up, and about 30-50 psi at around 40-50 MPH on the road. This morning I noticed the engine running a little hot when I got to work.

 

[xxthegonzxx]

Bueller....Bueller.....

 

[kopcicle]

First thing to do when suspecting low oil pressure is oil and filter change .
Inspect the filter for ferrous with a magnet
Inspect the filter for white metal (babbitt- bearing material ) by washing with phosphoric acid . Will foam a bit and turn black .
Inspect pressure relief . (hope you have the FSM , real good oil diagram in it )
If all else fails get rid of the multi vis oils and use a straight weight 30 .

YMMV

~kop

 

[xxthegonzxx]

Kop, thanks for the answer. I recently changed the oil and the oil filter. When I performed the oil change, I took off the oil pan for the first time and noticed metal shavings in the pan. Some of the shavings were pretty big chunks but all in all not bigger than a 1/4 the size of a dime. I just came back from starting my bike and the oil pressure was back at around 45 PSI. There's some minor leakage from around the gear shifter but I suspect that wouldn't cause the oil pressure to drop so dramatically. That's something completely different I have to fix. Luckily my oil light has not come on at all during riding or while idling but I will ride it home and see how it fares. The oil I use is Castrol 10w40 Full Synthetic.

 

[xxthegonzxx]

Also, as a note before this happened today I did take the oil pump off for inspection and forgot one of the metal O-ring collars a couple of weeks back. I ran it once and the oil pressure dropped to zero then the engine died. I quickly disassembled it and put it back on but that's when all this started. I'm pretty sure I have a lot of work to do this weekend and that will more than likely be the culprit. Is there anything I should check specifically with it that will help me get this working?

 

[Rich Ard]

Some of the shavings were pretty big chunks but all in all not bigger than a 1/4 the size of a dime.

You're fucked. Bummer, too. At some point you're going to discover what those large pieces of metal came from, and it may be loud.

Did you save the pieces? It's possible that our forensic analysts may be able to help you figure out whence they came.

Also fyi 'shavings' and 'chunks' are pretty distinct units of measurement.

 

[xxthegonzxx]

"You're fucked..." Yeah that's what I'm guessing.

Started it up at about 45 PSI idled well and the oil light didn't come on which is good. By the time I got halfway home the oil pressure dropped to about 5 PSI and by the time I was 5 minutes away from home I started to hear some hard rattling. Luckily I got home in time without it getting any worse but I won't really find out until I do a rebuild...I'm guessing once I do that I'm going to find some pretty bad damage

Unfortunately I didn't save the pieces...but they were sticking to my magnet when I had them....Not really sure what that means but I was told it might be bearings?

 

[Rich Ard]

It might be anything inside the case that's made of a ferrous metal.

Time to tear it down or put a replacement motor in.