Low Oil pressure after warmed up

[bwanna]

Hey all,

This is for my '82 GS450T, running 10-40w oil. outside temps avg'ing 45-70F.

Symptoms:
-Riding at local speeds around town the oil pressure light doesn't come on.
-Riding at highway speeds for short time light comes on at approx 1100rpm. (longer riding results in light coming on at approx 1400rpm.)
-After riding at highway speeds and then riding at local speeds (cooling down?) the light intermittently comes on between 1100-1300rpm
-After highway riding, then stopping for 5 mins (off) then restarting, no light.

So, it APPEARS the oil pressure gets lower as oil temp gets higher.

Work I've done:
-pulled oil pump and checked all clearance (good)
-replaced oil pump seals
-replaced oil and filter

Any ideas for cause? ... what I can check?

Thanks ahead of time!!
Jersey

 

[Nessism]

I'd look for a gauge so you can measure oil pressure. The light sensor may be flakey.

 

[bwanna]

I'd look for a gauge so you can measure oil pressure. The light sensor may be flakey.

DUH... Boy did I miss that one!

I could probably insert an attachment to the same location the pressure switch is located... at least for testing. Any suggestions/experience on placement?

Thanks!

 

[Guest]

On the right hand side of the bike there is a "Bolt" at the base of the cylinders.

That bolt plugs the oil channel.

You can screw adaptor and your gauge in there.

 

[bwanna]

On the right hand side of the bike there is a "Bolt" at the base of the cylinders.

That bolt plugs the oil channel.

You can screw adaptor and your gauge in there.

Ok. Great. I'll check that when I get home. Would be nice to have a permanent gauge anyway.

 

[Guest]

There was a tread recently about them.

The vibration kills them over time. But then they don't cost much.

 

[bwanna]

There was a tread recently about them.

The vibration kills them over time. But then they don't cost much.

vibration kills the pressure gauge you mean?

 

[Guest]

I would suggest you pull said bolt and take it to the hardware store, with your newly purchased gauge, so you can buy thea daptor(s) you need.

 

[Guest]

Yes.

Kills the gauge.

Here is the thread:

http://www.thegsresources.com/_forum/showthread.php?t=221045&highlight=pressure+gauge

 

[bwanna]

I would suggest you pull said bolt and take it to the hardware store, with your newly purchased gauge, so you can buy thea daptor(s) you need.

Am thinking of using a banjo setup with braided brake line to the gauge.

 

[chuck hahn]

And dont expect 30 PSI either..an average of around 5 to 7 PSI is what I believe the norm is according to what I have read here. And you can see if the wire is secure at the clip that attatches to the top of the sending unit.

Clean it and add a dab of solder as these crimped on connectors are exposed 24/7 and even though they look good can in fact be loose. A loose connection and the light will come on too.

 

[bwanna]

And dont expect 30 PSI either..an average of around 5 to 7 PSI is what I believe the norm is according to what I have read here. And you can see if the wire is secure at the clip that attatches to the top of the sending unit.

Clean it and add a dab of solder as these crimped on connectors are exposed 24/7 and even though they look good can in fact be loose. A loose connection and the light will come on too.

I'll check the connectors. Good idea re: solder. I've done that with bulb tips, but hadn't thought of that for this.

I thought the "T" model had a high pressure oil pump? According to the shope manual. Does anyone remember what the max PSI is for the 450T? I seem to remember it being like 80 PSI or something there about.

Thanks!

 

[chuck hahn]

I didnt look to see what bike you have..but I was quoting what I heard before here on the forum when reading posts. Maybe what i was reading applied to the 750s and 1000s. Does Bikecliff have that bikes manual on his site??

 

[Nessism]

The 450 has a plain bearing crank and a high oil pressure pump. Look in the manual for the pressure spec. It should be something like 60 psi at 5000 rpm.

 

[bwanna]

I checked Bikecliff and my Clymer manuals, but no joy.

 

[Guest]

Its in the Haynes manual on page 115.

Pressure should be high for this engine,

Here is what it says.
"
Run the engine at 2000 rpm for 10 minutes to warm it up.
Then run the engine at 3000 rpm,
Pressure should be 42.7 to 78.2 PSI.

A pressure reading lower than specified may be caused by a worn pump, a blocked oil strainer or oil filer element. OR installing it backwards !! ( long story )
"
A slow decrease over time is indicative of bearings wearing out.

I'm going between internal leak, pressure regulator weak spring, or faulty pressure sensor. I've seen all 3 do this on mine.


Roller bearing engines run on low pressure high volume. So 5-7 psi is normal for those.

 

[bwanna]

Thanks so much! Maybe I should get a haynes manual?

That gives me something to work with!

 

[Guest]

Thanks so much! Maybe I should get a haynes manual?

That gives me something to work with!

Its on his site, Listed as GS400-450 and 250, There is two on there, I sent him the two I had and I think he already had them on the second page of manuals.

Also get the gs500 manual. Nearly everything is applicable if not more advanced in terms of knowledge and experience. I mean the oldest manual is still 7 years newer than the one made the year of your bike.

 

[bwanna]

So I installed a permanent oil pressure gauge as suggested earlier.

Average max pressure during warmup is about 70psi, with cruising pressure about 50psi and idle drops to about 35-40ps. So this correlates to what the manuals indicate.

After warmup things change. Once the things are hot avg cruise pressure is about 40psi with idle dropping to 0psi... with light coming on.

As mentioned earlier, if I let the bike sit for just a few minutes, the light goes off, but the gauge still shows 0 psi at idle. I chock this reading to the fact that the gauge has about 8 inches of hose to the side plug.

SOOOO... any ideas on what I can check? ... tests I can do to determine the cause?

Thanks,

 

[GregT]

tests - no,not really. causes IMO in order of probability...

Sticking pressure relief valve - sorry but this is an engine strip to get to it, not accessible from outside...

Worn pump - this is accessible but involves removing the clutch.

Those two i'd pick as most likely causes. If you pull the pump, don't forget to renew the O rings sealing it.