TOPIC:

steell wrote:

In answer to your example question above, you just increase the flow.

If excess pressure was good, then engineers would not include a pressure relief valve in the engine oil systems to dump that excess back to the pan. Obviously 2.8 PSI is enough to do the job on the 900/1000/1100 motors, because that is the spec in the manual and it works.

A large number of people freak out when they put a pressure gauge on the roller bearing motors and see really low numbers like 3-6 PSI because they are accustomed to the 30-40 psi on cars with plain bearing motors.

Sure you could increase the resistance to flow (and thus increase the pressure) by restricting the flow to the main bearings, but the bearings wouldn't like that at all.

You do realize that you are saying that there should be more pressure shown on the gauge just to make you more comfortable?

Not really. I have done some engineering with fluid flow in systems (including airflow in thermal chambers) and you do need some back pressure to get a uniform distribution in any system where the flow outlets are dissimilar in resistance to the various outlets.

If you say it works OK, that's fine. It just makes me nervous because if your nominal pressure is 3 psi, you are REALLY close to ZERO in your operating point. If anything changes slightly, it could drop slightly and the feed points downstream would get nothing.

BTW, I realize that most automotive oil pumps have a "pop off" valve (spring loaded steel ball bearing) to allow oil to bypass and return to the pan which caps maximum oil pressure. Of course it would be needed, because the wide temp range means the oil will cover a wide viscosity range and the wide RPM range the pump is driven from means the pump could put out a very high pressure cold if left totally uncontrolled, and that would not be a good thing. No question the pressure should be kept in a usable range.... I just prefer that my nominal operating point not be 3 psi away from ZERO.....

f you say it works OK, that fine.

It's not me saying it's fine, it's Kawasaki saying it
And the longevity of the 900/1000/1100 motors verifies it in my opinion. But like I said before, the low oil pressure numbers on the 900/1000/1100 scare people because they are used to the higher oil pressure in the plain bearing motors in their cars.

What ought to concern you more is the lack of cam bearing shells in the 750 twin (and the 650/750 fours), lose oil pressure or flow for any reason and you need a new head. And after prying enough aluminum off the cranks of Kohler motors when the aluminum rod seized on the crank (no bearing shells), I'm a little paranoid about the cams riding directly on the aluminum head.

steell wrote:

What ought to concern you more is the lack of cam bearing shells in the 750 twin (and the 650/750 fours), lose oil pressure or flow for any reason and you need a new head.

Maybe so, I haven't heard that to be a common problem. BTW, I found a good 750T head complete with camshafts and valve cover for $100 at one of the junkers back when I was rebuilding mine (scouting parts just in case my cam journals were worn). I asked some of the old pros and they said they never saw the cam bearings wear out on them and when I checked mine it had no measurable wear.

Mine has about 80k miles. I did plastigauge all the camshaft caps and journals and they were all still nominal clearance. Whatever hardening process they use on the aluminum bearing faces must be damn good.

From what I've seen, more heads go to the great junkyard in the sky because the valve clearance gets too tight and the valve seat burns up.

Heres another thought.it takes H.P.to generate oil pressure.Thats why most automotive racing engines and the Cummins BIG truck engines go for high volume/low pressure oil systems.to much oil pressure is actually bad for conventional insert type bearings.

76 LTD wrote:

Heres another thought.it takes H.P.to generate oil pressure.Thats why most automotive racing engines and the Cummins BIG truck engines go for high volume/low pressure oil systems.to much oil pressure is actually bad for conventional insert type bearings.

I wish you hadn't brought that up, I "really" don't want to go into the physics behind that

Yes, I know that's true, and yes, I know why, but I'm only a two finger typist and my poor fingers can only handle so much

Several thoughts for you...

Pull your oil filter and make sure there is both a spring and a washer under the filter.

Pull your oil pan and clean the oil pickup mesh screen.

If you are running an oil cooler, remove it. The cooler will reduce effective oil pressure.

Have you made any modifications to the bike?
Some people put shorter rear shocks on the bike and lower the rear - this also moves the oil further back in the pan.

Geesh Jeff! I never thought about it but would a real fat posterior (which really compresses the shocks) do the same thing? Cause all the oil to run to the back of the pan or in my case probably out the breather as I punish those ol' shock? Hey, on a more serious note, that grab thingee that fits on the shock mount and rear turn signal perch really does the trick. MUCH MUCH easiest to pull the KZ900 up onto centerstand! I am delighted. I wish they had a longer grab piece for the shafty...

The oil light problem came on at the end of last years riding season,so i've been working on the problem this season,first changed the oil sender unit with a new one,put a oil gauge on it,pulled the oil pan,clean inside...took the oil pump apart,no glaring problems there,put an oil pump on it from a 1984 GPZ 1100, supposed to have 40 % better flow according to oldkawman,turns out that was B.S. same pump internally,body,gears, nothing different , other than relief valve on side of casing. ,put it back together,fresh Castrol 20-50 oil,new filter.It would start cold at about 5-6 lbs. pressure and after warming up drop off to about 1-2 lbs.at idle (1300 rpm) even at 3000 rpm at about 60 mph still only about 2 lbs. pressure,which,ok i can live with that.Stopped for fuel ,turned it off,got gas,started it back up,oil light on,gauge at "0",shut it off,waited a minute,restarted it-same thing no oil flow....???
I did order a washer to go under the oil filter,since mine isnt there,and a new K&N oil filter,but there must be a bigger problem than that.The oil pump is gear driven so it has to be turning,the gears should be pulling oil in and pumping oil out to the engine,could there be some blockage somewhere plugging up the oil supply? Could the engine gear NOT be turning the oil pump gear?
Any ideas? Would motorcycle specific oil be better than using regular car oil? I have used it in the past and it makes the clutch smoother on releasing, but its like 2 -3 times the price.

Oil pressure relief valve? I didnt think older KZ's had that,isnt it just open from the oil pump gears out to the end of the pump? I havent seen any springs/check valves or anything that would "set" the oil pressure other than what the turning oil pump gears will do.Is my oil pump missing something?

The gauge is new and seems accurate (0-15 psi).Kawasaki put the engine together in 1980.Can the oil journals be cleared with air pressure on a fully assembled engine? or do you mean like blowing air thru the crankshaft holes and passageways while its apart? can any of it be cleared that way on an assembled motor?

wiredgeorge wrote:

Take off your valve cover and look at your cam shafts. Any signs of wear on the lobes? Are the pockets in the cylinder head where the buckets lie full of oil. I doubt you have a problem. The oil pump on a 903/1015 pushes enough oil up through the oil journals to keep the cam shafts wet and there is very little pressure. I wonder how accurate a pressure gauge is with little pressure. If you are the one who put this engine together, did you make sure the oil journals were clear using compressed air?

The gauge is new and very accurate actually (2-15 psi).Kawasaki put the engine together in 1980.Can the oil journals be cleared with air pressure on a fully assembled engine? or do you mean like blowing air thru the crankshaft holes and passageways while its apart? can any of it be cleared that way on an assembled motor?

the only preasure releaf valve that i know of is an oil bypass in the oil filter cavity.if the oil filter plugs the oil preasure will build and push the spring and ball up to allow flow.
it is normal to have more preasure when the oil is cold and thicker and as it warms up the preasure will drop.u said u do not have the o ring on the oil pump ? if there is oil leaking there it will loose preasure.
where did u read that the 84gpz pump fits the kz? i like that.did u find that they look identical? is yours a mk11 type motor?
do u have oil at the valve spring area ,as George suggested?
What was the gear to body clearance,and gear to lid clearance, in the oil pump when u measured it?