oil pressure light on at 1800RPM and below?

I've got my bike back together and running. The oil pressure light is coming on ~1800RPM and below and turns off at ~2000RPM and above. The sump was removed and reinstalled with a new filter and OEM gaskets but is leaking a good bit. I'll pull it off and reinstall with RTV to stem the leaking. Could this be causing the low pressure at the lower RPM range? It worked fine before draining all the oil. Any thoughts on what I should check? Thanks.

These engines have roller bearing cranks, 2.2 to 2.8 PSI is usually the range. Tried a low pressure gauge to see if it's meeting the specs?

When you had the pan off, did you check the oil pump for wear?

What work was done? Have you checked the oil level since you ran it? Do you have an oil cooler installed? If you drained the engine completely, there's a possibility that you just had to purge all of the air out of it and this will drop your level. If you had a serious oil flow problem (that's what your oil light is really telling you on these bikes) you would be hearing it by now.

The topend (head and block) and sump were removed, cleaned, and reassembled. rebuilt carbs. I've got good compression on all cylinders. bike runs with no strange noises. It's running rough because the carbs are not synced yet. No cooler. Oil level is OK -- high if anything.

I did not touch the pump. Since this wasn't a problem beforeI figured that it was fine. I don't have a low pressure gauge. I'm planning on pulling the sump off again to get a better seal. Went back to check out a few things and light would come on at about 1500RPM and turn off above that.

I'd say there's about a 83.764593% chance that the oil pressure switch is the culprit. If it's picked up a tiny amount of debris, it will not register properly and will give false warning of low pressure. My CB350F suffered from that back in 1985, and the hotter it got the higher it had to rev to keep the light off. Until I fitted a new sensor/sender/switch/whatdoyoucallit and all was good.

So you are pulling the entire sump (oil pan) off? Take your time and make sure everything is clean and seated correctly.

richrand wrote: I've got my bike back together and running. The oil pressure light is coming on ~1800RPM and below and turns off at ~2000RPM and above. The sump was removed and reinstalled with a new filter and OEM gaskets but is leaking a good bit. I'll pull it off and reinstall with RTV to stem the leaking. Could this be causing the low pressure at the lower RPM range? It worked fine before draining all the oil. Any thoughts on what I should check? Thanks.

"...I'll pull it off and reinstall with RTV to stem the leaking...."

Did you use RTV or some other such stuff when you assembled the engine? Could it be that some of that muck broke loose and is clogging up your bike's oil flow? Ed

DO NOT USE RTV, the pan will seal with just the gasket. It's been said before but make sure everything is clean and all old RTV is off. RTV breaks free on the inside and gets into all sorts of places it shouldn't.

Might want to pull off the whatsit that the oil pressure switch mounts to and clean that and the switch out while you are at it.

baldy110 wrote: DO NOT USE RTV, the pan will seal with just the gasket. It's been said before but make sure everything is clean and all old RTV is off. RTV breaks free on the inside and gets into all sorts of places it shouldn't.

X2

You didn't by some chance forget to install the big o ring on the pan did you? That will definitely cause that particular problem.

I installed an OEM spec gasket with copper spray on both sides. There was only what seemed to be the original gasket on there (no rtv) which I thought i'd removed completely. I wiped the surfaces with acetone before reinstalling. I did install the filter o-ring. I'll drain the oil and do it again with a new gaskets. I that doesn't work, I'll pull the sensor.

LarryC wrote:

baldy110 wrote: DO NOT USE RTV, the pan will seal with just the gasket. It's been said before but make sure everything is clean and all old RTV is off. RTV breaks free on the inside and gets into all sorts of places it shouldn't.

X2

You didn't by some chance forget to install the big o ring on the pan did you? That will definitely cause that particular problem.

Argh FML! Thank you, Larry. This is exactly what I didn't do. Will do this today.