Oil pressure - WTF!? K6 1200

[Octane]

Hey All,
I've installed a mechanical acting 0-100PSI oil pressure gauge today. Went to all the trouble of stainless braided line, Speedflow fittings etc. $150 total install cost (gauge & line). Fired up the 1200, oil pressure was a pleasing 60PSI idle cold. As the engine warmed up watched the pressure slowly drop 55, 50, 45, 40, 35, 30, 25 (WTF!?), 20 (fark!), 15, 10 shut it down there and then.
The oil light switch is still installed and no light came on. OK, go for a ride. 3000rpm gauge shows 40PSI, between shifts I see the gauge momentarily drops to about 20PSI and back up to 40PSI. STart cruising at 2500rpm pressure shows 20PSI. By this time engine is well and truly warmed up. Stop at the lights and idle. Watched the gauge bury the needle at a big fat ZERO!. WTF!? No oil warning light on. What is this? Went straight home and pulled the other B12 out from hibernation. Fitted the battery hooked this gauge up to it and tested again. Exactly the same outcome. Either this gauge is not right OR the B12 runs freaking low oil pressure when hot or both my 1200's have identical serious problems. Running 15W-50 fully synthetic oil, K&N oil filter, both engines have done approx 9,000km.
Has anyone else done this exercise in cardiac arrest provoking behaviour?

[PaulVS]

Wait.... Both your bikes run fine, but your freaking out because your new fancy oil pressure gauge is telling you you have no oil pressure?

Hmmmm......

 

[pmackie]

Hey Octane

Where did you install the pressure gauge? Are you getting an accurate measure of pump pressure?

Also remember, "pressure" is a measure of resistance to flow. In a closed system, all other factors being equal, pressure times volume = constant. So a drop in pressure would result in an increase in flow. Unfortuneately in this case, the oil itself is changing (lower viscosity) as it heats up, so too many variable here. blah, blah, blah

Sorry...rambling a bit here this morning...    What I'm trying to say is that the pressure is less important than receiveing adequate flow to the critical parts...in this case sufficient flow to the cams and rockers.

Does the workshop manual list recommended pressures at any specific points? I never put a gauge on my 600 so I have no specific data.

[Octane]

I installed it into the main oil gallery. See pictures.
Specification is 40-80 PSI at 3000rpm at 60 deg C.
Also watched a youtube vid of a guy checking oil pressure on his gixxer 750 with identical results to me.
 

[rider123]

As the engine heats up so does the oil which makes it thinner which means its easy to push around for better flow which is what you want. Perfectly normal. In fact I'd be worried if it didn't go down as it heated up which would mean you have a blockage somewhere. Reading should always be taken when the engine and oil are fully warmed up. Also the main oil gallery is a low pressure centre on the bike the readings would be consistant of that fact. Since the main oil gallery is right near the sump you can tell immediately if you have an oil leak or not. But at idle there would be little oil pressure in that area of the bike as it's basically the resevoir. If there is a way to put it on say a higher pressure area that is more critical such as the top end that might be better. To be honest a pressure guage on this type of engine is more for the cool toy factor than real information. I would trade it for an oil temp sensor instead. The only real reason you would need an oil pressure guage is at high rpm racing in which the slightest bit of drop in oil pressure could mean catastrophic failure of componants. At normal RPM it would probably say zero in that area of the bike which has the least amount of pressure. This engine has 2 oil systems. A low pressure, high volume system for cooling the engine. And a higher pressure low volume system for lubrication. You put the guage basically in the resevoir which would have the lowest pressure, however it's still usefull as you can see what kind of pressure the whole system has to cool/lubricate the systems. However it doesn't look "cool" having zero oil pressure so I would consider changing the sensor where the guage is to a higher pressure part of the bike so you get better readings for your guage.

Also every bike is different a 20psi at cruise for you might be catastrophically low for another bike. So the guage is really there for you to judge what's out of the norm. So say you start cruising around and now it's 15psi instead of the normal 20psi you know you're low on oil. If the guage jumps to 30 or 40psi at cruise you know you have too much oil or have a blockage somewhere. In fact you've already helped yourself. You know that at cold startup you should be around the 60psi level. If you're lower or higher you know you have a problem. Since you do a bit of drag racing the guage should be fine. I'm sure at 9000 rpm you probably should be around the 60 or 70 psi level.

[sandy klock]

oil pressure is generally ten psi per thousand rpm as a rule of thumb for bikes up to the relief valve setting at which point there is no increase in pressure with increased rpms.  you have a long line full of air that compresses. like a mushy brake line with air in it.  alot of these gages are installed at crankcase direct without lines.  another idea may be a sending unit at case and a wire to gage.  I think you are hooked up in rite location.  Gage looks good.  and there is adequate needle sweep to get to twenty psi to show indication.  A washer in bypass valve will increase spring tension in minimum setting on oil pumps on other bikes. did you use the recomended line diameter? a small line holds less air. 

[sandy klock]

the previous posts are correct that gage gives good indication of loss of lubrication at operating rpms.  Most critical. Also you dont want excess oil press.  it does no good. robs hp.  A gage that reads closest to max psi is generally best  perhaps a 80psi would have been a better match in this case.  Good luck