TOPIC:

KZ Riders,
I am new to oil pressure gauges. Thought I'd come to you all with this and see if some of your experience can help me out.

I acquired an 1978 KZ1000 engine a while back and it came with a Marshall engine oil gauge installed. Problem was that the gauge was on a scale of 100 psi, so it hardly registered anything when the engine ran.

So, I ordered a new Marshall gauge that goes up to 15 psi and installed it. It's in the standard place, mounted to that oil port below the fourth cylinder.

As I understand it, the gauge is supposed to read around 3 psi at around 3,000 rpm, at 140 Fahrenheit.

This is what mine does (10w-40 oil, about 3.7 liters-- no oil cooler or other engine modifications):

When I start the engine cold (in January), it reads very, very high-- maxing out if I blip the throttle at all.

Once the bike has warmed up and reached a steady non-choked idle, it will read about 3 psi at about 3,000 rpm. I don't have a thermometer to measure the temp with, but I assume this is in the regular operating temperature zone, since the bike has warmed up and is idling as it should.

When I ride the bike, it seems to hold a steady 3 psi when I'm going down the highway and I have the bike right where it needs to be for cruising-- between 3,500 and 5,000 rpm.

But then, I have notice that after I have ridden for a good long while (maybe 30-45 miles), I'll look down and the oil pressure gauge will be zeroed out. No pressure whatsoever.

I have noticed that the gauge will also tend to do this after I have traveled down the several miles of dirt roads that lead to my home. Crawling along these roads with little air traveling over the engine tends to make things hot.

It is important to note that the stock oil level light (which I believe does work properly) never comes on when this happens-- so I assume my oil level is good. And there's definitely oil visible all the way to the top of the engine oil viewer window.

So, my current theory is that the gauge effectively stops reading pressure after the engine gets pretty hot. It must be that the oil is thicker when cold (hence the high pressure readings on cold starting), and gets progressively thinner the hotter the bike gets. And so there is only a window within that thermal/viscous progression in which the gauge is useful.

Is this right? Is this in keeping with the experiences of those of you who have had these oil pressure gauges mounted on your engine?

I like my theory and I think it makes sense, but it leaves me wondering what purpose these oil pressure gauges serve and what the most useful way to use/read them is. What you all think? How do you make use of these gauges?

Also, I want to make sure something crazy, like a failing oil pump or some kind of oil port blockage, isn't behind this weirdness. Or does this kind of intermittent reading mean something else-- like a need for a new oil filter, or something like that?

In any event, I'd very much like to hear what thoughts and experiences there are out there on this.

Thanks.

Enjoy the bike and dont worry.
I use a 15 psi gauge and have the same results . Other than my gauge always shows some pressure ( 1 or 2 psi ) or 3psi hot and at speed ( rpm )
These motors rely on FLOW , not so much on pressure
If the light isnt coming on , ride it Dave

Yes! don't worry it's normal.
Depending on oil grade and temp the gauge will read pretty high when cold and more or less nothing when hot.
Mine reads off the clock on start up with Rock oil TRM 20/60 then close to zero at idle when hot.

Street Fighter LTD wrote: Enjoy the bike and dont worry.
I use a 15 psi gauge and have the same results . Other than my gauge always shows some pressure ( 1 or 2 psi ) or 3psi hot and at speed ( rpm )
These motors rely on FLOW , not so much on pressure
If the light isnt coming on , ride it Dave

^Yep, that.^

The pressure sensing switch is lifted off it's seat by low-pressure flow. As long as the oil light is off there's flow. Most of the pressure in aircooled Z motors is built from resistance to flow in the solid cam bushings. Otherwise, resistance to flow is very minimal through the open needle & ball bearings everywhere else that rely on flow instead of pressure to survive.

Mechanical gauges in the consumer market are notoriously inaccurate at the lowest & highest 10% ends of their range. Sounds like OP's is working correctly in our experience.

Good Ridin'
slmjim & Z1BEBE

I've blown two low pressure gauges. They looked good but just couldn't handle the higher pressure at startup. In 13 I went through the pump, sanded the plate with #600 paper on a sheet of glass, switched the gears, thinner gasket and had 40+ PSI when cold blowing the gauges. I got a Harley 60 PSI gauge but the glass was plastic so it lasted only a year in the sun. I use 15-40 oil so when it gets hot the gauge reads 2-3 PSI when hot. More important was the idiot light. My switch was 40+ years old and new ones were crazy money so I took a chance and bought a later J model one used to see if it would work. $15 and it works flawlessly. I have a new 60 PSI Marshall oil filled gauge but it's more for looks than anything else. It does tell me however if I'm low on oil by fluctuating at idle. It's more sensitive than the switch. I'll get a 30 PSI one for the dash being it's far enough away from the engine it shouldn't be damaged by the high pressure spikes at startup. Everything said here is correct. It's a high volume system not high pressure.
Steve

Thank you all for your input. I'm glad to hear this is normal.

SWest: nice bike, thanks for the pictures. Also, if it helps, the Marshall gauge (0-15) I'm using has held up against the high pressures of cold starting, so maybe that would be a good option. I'll let you know if it blows.

So, like I said, I really appreciate all the input. What would be the best way to make use this thing (other than cosmetics)?

I was sort of enthusiastic about having this gauge because I've always been bewildered by the KZ 1000 oil level window. Whenever I change my oil, the amount of oil called for (I've been putting in about 3.5 quarts if changing oil without a new filter, and 3.7 liters if changing both oil and filter) more than fills the oil level viewing window, rising well above the high mark.

So, when the bike has the correct amount of oil in it and it's standing upright, either on the center stand or with me holding it, the oil level in the window completely fills the window, passing beyond the high level mark. Given this, I've long been unsure how to exactly gauge the level of oil in the bike-- and I want to try to avoid over filling, as I think the first cylinder has a leaking valve guide seal and I don't want to encourage oil fouling/burning (I plan to fix this, but won't have time to do it for a while).

So all of this is to say that I hoped this gauge would give me a more accurate read on the state of lubrication in the engine.

I was thinking that I could do something like this: if it goes significantly over 3 psi during that engine temp/cruising rpm sweet spot, then it might be over filled; if it goes significantly under, or never reaches around 3 psi during that engine temp/cruising rpm sweet spot, then the oil may be low.

That sound like a fair approach?

How do you guys read yours?

Also, you all have the same experience/frustration with your oil level viewer window? If so, how do you all make use of that?

Thanks-- appreciate your thoughts.

Use center stand or have the bike held upright Then
check oil level which for me is to the top line seen at sight glass.
Dont over , or under fill.
To much oil will NOT increase oil pressure. But it might make the oil foam up which could possible lower oil pressure ( Probably not , but dont do it )
To low of oil can be a problem by starving oil pump during acceleration as the oil pickup is not at the rear of the motor.
Some of us Hot rodders install a hinged gate in our oilpans to keep oil from going to the trans area of the sump during fast take offs.
If more questions , Ask away
Dave

This is the hinged gate Dave is talking about. It´s my first must have mod i do on the engine in the late 90th.

That seems like a useful mod-- and I might do it, as I love to take off hard. Thanks.

With the oil level window: I'm just putting the amount of oil called for in the bike (about 3.5 quarts) and the level totally fills the window, going beyond the top mark (with the bike on the center stand or held upright).

I think that the oil level is actually far too low (maybe only three quarts or so) if I stop filling when the oil level hits the top mark. I'm not trying to over fill it-- I'm only putting in the amount of oil called for.

This is the second 1978 K1000 engine I've dealt with that is like this.

Anyone else run into this?

We don't adhere precisely to exact oil volume specified by Mama Kaw at oil & filter change.

We pour in 3 qts., start, idle for a couple minutes, to make sure the filter cavity is full, shut down & wait 10 minutes or longer for draindown while we dump the old oil in the waste oil barrel, check/adjust the chain, put tools away etc. After the shutdown pause we top off the oil to the upper line in the sight glass, & check it again after about a minute. Top off as necessary. All done on the centerstand. We really don't pay close attention to exact oil volume.

Good Ridin'
slmjim & Z1BEBE

That's great-- thanks a lot. I will definitely do this at my next oil change.

Seems like I may have been over filling my bike all these years, adhering to Mama Kaw's specs.

What's up with Mama Kaw's oil specs? They call for too much oil for some reason? Anyone know the reason for this?