Topic: Oil pressure problem

[Sething]

Oil pressure light won’t go out after putting the engine back in the frame and hooking everything back up.
I’ve ruled out the wire running to the switch. Light goes out when I disconnect it from the switch.
I’ve also tried pouring oil at the top of the cylinders through the tappet covers and down the galley plug hole to try and prime the oil pump. I ran the starter for a bit then ran the engine and it’s still on.
I’m concerned the oil pressure isn’t building up enough to flip the switch.
Any additional ideas?
Thank you.

1977 Honda CB750K



Honda 1977 CB750K

[DaveBarbier]

Open the top caps with the engine running and look for oil splashing around. You will get oil splashing just from the cam lobes scooping oil up from the wells but there will be even more and it’ll keep coming. Maybe shoot a video.

[calj737]

Check your wiring. The Blue/Red wire is a ground.

[Sething]

Thanks Dave, I’ll open them up and check for oil splashing around.

Cal, i think the wiring is ok. The light goes off when I remove the blue/red ground wire from the switch. Also just to make sure it wasn’t a bad switch, I replaced the switch with a new one and I got the same result, which tells me it’s not the switch. Based on prior posts, if the wire was bad or grounded, the light would stay on when disconnected from the switch. You’re the wiring master, so let me know if I’m missing something. (As you know I’m using the M unit and have it hooked up exactly like my neutral switch)

I’ll try to take some video or pictures so you know what I’m dealing with.





Honda 1977 CB750K

[Patrick]

Yes, please take a video of you pulling off the valve adjustment covers with the engine running. I was not taking a video the day I power washed my garage wall with the motor oil from my CB750. I want to know how it looks.

Patrick

[Sething]

LMAO, thanks Patrick.
To be honest, I would hope that happens given I’m not sure if it’s getting oil at all.



Honda 1977 CB750K

[Patrick]

What did you do to the engine when you had it out? If it was a rebuild - or even if you just drained all the oil - it can take a while for the oil pressure light to register. Did you start the engine? How long did you run it? If you are just trying to read oil pressure using only the starter or the kick starter you may kick all day. Run it for a while. See if the light goes out.

Patrick

[Sething]

I took it out to do a complete powder coat of the frame. The engine was running well with no leaks or problems so I put it right back in without doing anything to it. I did drain the oil completely before I took it out. I also replaced the filter. I ran the engine at idle for a little while but have been hesitant to run it for more than a couple of minutes at a time.
I need to fix the float height in my carbs anyway so once I do that and have it idling smoothly, I think it will be safe to run it for a more than a couple of minutes in order to see if it eventually shuts off.


Honda 1977 CB750K

[ekpent]

  If all is good and oil pumping you should also see circulation,bubbles etc. in the oil tank if you take a peek inside with a flashlight.

[Patrick]

It shouldn't take a couple minutes. Thirty second should do it. Since you did not work on the engine, and it ran when you pulled it, I am beginning to suspect something electric, as well. It is possible, if the engine has never seen work, you had some silt in the bottom of the engine that got stirred up when the engine was out. You could pull the oil pan (doable with the engine in bike) and check the screen at the bottom of the oil pump.

Patrick

[Sething]

More good suggestions. Interesting that it should work quickly to turn it off. I’ll start checking off the list of suggestions and report back.



Honda 1977 CB750K

[bryanj]

How long was the engine stood? If a long time perhaps the pump has drained out and needs priming. Are hoses on correctly?

All mistakes i have seen over 40 years

[Sething]

Ok here’s the deal so far.
I put some oil in the top through the tappet covers on the top of the engine and some in the hole worth the galley bolt. I started the engine and let it run a bit with the tappet covers off. I was expecting oil to shoot up or out but I don’t see any oil when the rockers are going. (See pic)
Also I looked inside my oil tank and there’s a lot of activity and bubbles. However, I’m wondering now if I have my hoses are installed correctly. I have a custom oil tank I installed from Cognito Moto. (See pics)

So essentially I have activity in the tank but it seems like nothing is reaching the top of the engine valves. I was hoping to have a mess.
I did not take the pan off to look at the oil pump filter/screen.



Honda 1977 CB750K

[Sething]

Follow up.
I looked at the installation for the oil tank and it’s correct. Phew!
Which means I may have an oil pump issue?



Honda 1977 CB750K

[Sething]

Update for anyone who may have this problem in the future: a week later I’m working on trying to prime the oil pump and I decide to take a look at the placement of my oil tank hoses to the engine. Lo and behold, they were wrong. I switched them, leaned the bike over on the kickstand, filled the galley with oil and the top of the engine. I alternated between the kickstart and the starter with the kill switch on for about 20 minutes and the light went out. (Slight yelling coming from side of the house)
Not sure why I saw the oil hoses as correctly placed last week but my only excuse is that I’m taking care of two toddlers and my mind is very tired most of the time.



Honda 1977 CB750K