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TOPIC: Revisiting Oil Pressure Gauges

Revisiting Oil Pressure Gauges 2 weeks 4 days ago #27815

  • rdurost
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Given the recent discussion about pressure and level sensors, it seems like an opportune time to ask once again, what the heck is up with oil pressure on this engine.

There were several posts in the past where it was said that an oil pressure gauge on a 1300 was a waste of time because it would always read low. In effect, it was maintained that these engines "don't need pressure, they just depend on oil volume." This has never made any sense to me. In terms of the world of engines, there isn't a lot that's too exotic about the 1300. It uses plane bearings just like a car engine, it has a wet sump, an oil pump, and a large oil pan on the later models (like my '82).

It seems to me that an oil pressure gauge would give more useful information than an "idiot light," not even asking why they thought it was a good idea to have both oil pressure and oil level sensors register trouble through the same single light. My '89 5.0 Mustang has both a pressure gauge and a level warning light, and they complement each other very nicely.

So would somebody please enlighten me on how this understanding of how oil pressure works got out there in the first place, if there is any validity to it, and WHY?

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Revisiting Oil Pressure Gauges 2 weeks 4 days ago #27823

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RE: Oil Pressure guage.
Two yrs ago in preparation and anticipation of installing a spin-on oil filter adapter/cooler I installed a press. and temp guage.
My '80 just rolled over 89,000K. I use Shell Rottella 20/40. Prior to the adapter: Oil psi at start: 65/70 psi. The oil pressure relief valve limit is 70psi. On the road the psi was typically around 30 psi. At idle.......as someone once pointed out; "heart stopping."
PSI needle was barely off the pin. NO oil light ! Oil temp would routinely be 75+c.
With the adapter: Same 65/70 psi at start. On the road: 40+ psi. At idle 8/10 psi. Oil temp. 60/65c.
My PSi gauge was originally installed in the notch between the crank-case and clutch. Seemed like a good idea at the time. Because I was routinely checking the PSI for evaluation reasons I found this placement nothing short of dangerous. I moved the gauge up to the side of the instrument cluster. Eyes can remain on the road !
Should mention: The filter adapter requires an additional 600ml of oil which MAY assist in some lowering of the oil temp. but I doubt this amount is aiding in any significant way.
Coolant temp. runs about the same in slow traffic, but on the hwy is lower - just into the operating range. I attribute this to the oil cooler and external filter.
It's clear to me that there is a (obviously) direct relation to the oil pressure, oil temp. and coolant temp.
An oil psi gauge is easy to install with a "Tee" at the oil psi switch. Placing the gauge up by the cluster is also simple.
Do you need a PSI gauge? That's up to the individual, but if you decide to you may want to invest in a portable defibrillator!
The install of one could warn of a potential internal problem.
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !
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Last edit: by scotch.

Revisiting Oil Pressure Gauges 2 weeks 4 days ago #27827

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I’ll take a crack at this question purely from a theoretical point of view.

Under what circumstances do combustion engines require oil pressure?
1. Almost all engines over 10 HP require oil pressure at the connecting rod journals to supply oil under pressure to the connecting rods so that the relief notch on the side of the connecting rod or a drilled orifice on the top side of the connecting rod big end, gets exposed to the drilled oil journal on the crankshaft connecting rod journal to(for lack of a better word), squirt oil on to the cylinder walls while the piston is up near top dead center to lubricate the cylinder walls prior to the piston exerting sideward pressure on the cylinder wall.
2. Another need for oil pressure would be in an engine with hydraulic lifters to fill the lifters with oil in a limited amount of time when the lifter is not under pressure from the valve springs.
3. Some high-performance engines with turbochargers or superchargers have oil cooling to the bottom of the pistons supplied by a pressurized oil gallery with spray nozzles
4. Some engines also have camshaft chain tensioners which have a minimum tensioning spring with an oil pressurized piston backing up the tension rod to force the tensioner out against the cam chain roller keeping the chain tight. The Zn1300’s have an oil supply line to the back of the cam chain tensioner but I’m not sure if in this case it’s to supply “pressure” to the tension rod or if it’s to supply oil flow for some other reason. My Porsche928 has 3 tensioners (2 on the cam chains and one on the timing belt tensioner) that require oil pressure to do their jobs.
5. Last but probably not least, oil pressure is required to push oil through the oil filter media. If it weren’t for oil pressure, the surface area of the filtration media would be too great to filter the oil without pressure unless a centrifuge is used. The older 1970’s 4 stroke Hondas come to mind since they used oil centrifuges on the end of the crankshaft. (prior to the 750cc Hondas which had cartridge filtration)


all engines require oil flow for several reasons. Most engines run plain bearings or roller bearings where needed which do not require any oil pressure. They require oil flow to –

1. Provide in the case of the plain bearings, oil to the bearing journal and shaft running in the journal just prior to the loaded area of the shaft and journal so that an oil wedge can be developed to cushion the loaded area between the two.
2. Provide a flow of oil to cool the moving parts and remove the heat to areas of the engine which dissipate the heat like the crankcase, cylinder head and valve cover, or to an oil cooler if available.
3. To remove unwanted debris for the engine internals and transport to the oil filtration system for removal.
4. Provide oil to coat parts of the engine in a rust inhibiting barrier when the engine is not operating.
5. In the case of roller bearings, lubricate the surfaces of the outer race, inner race and rollers and remove heat from the bearing.

Why do most engines monitor oil pressure and not oil flow?

Oil pressure is developed when the flow of the oil from the oil pump and after the oil filtration system overcomes the flow through all the clearances in the engine.
An oil pressure monitoring system is simpler than an oil flow monitoring system.

Why would you want to monitor the oil level in the crankcase if oil pressure and oil flow are more important?

My educated opinion here would be that the assumption is that oil pumps seldom fail and if the oil filtration system gets plugged, the filter bypass valve would open up allowing oil to still flow. So if we can pretty much guarantee that we have oil pressure and oil flow just by design then the only other problem that comes in to play with the oil system would be not enough oil to remove excess heat from parts causing an engine seizure. I believe that in their ultimate wisdom Kawasaki decided that lack of oil quantity was even more critical to monitor than a possible failure of the oil supply system. By removing the oil pressure switch, they simplified the oil monitoring system from identifying 2 possible failures (low oil pressure or low oil level) to 1 single failure low oil level. It’s also my opinion that this was a move backwards. Monitoring oil pressure while driving will indicate a problem before it becomes a problem if you know how to interpret the information.

That’s all I got. Feel free to chime in.
KB
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Last edit: by Kawboy.

Revisiting Oil Pressure Gauges 2 weeks 4 days ago #27828

  • Bucko
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Oil pumps may seldom fail but they do wear - they're typically pumping unfiltered oil after all (not sure if that's the case in a 1300 or not). My old Honda will light the oil lamp on a hot day if the oil 'weight' is too low - a sure sign the oil pump is worn - which is not uncommon on those bikes (replacement pumps from Honda are no longer available, but the wear typically occurs between the side of the 'rotor' and pump body so if the rotor lobe are good, the pump body and rotor side faces can be re-machined to reduce pump losses)
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Last edit: by Bucko.

Revisiting Oil Pressure Gauges 2 weeks 3 days ago #27835

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Hey Scotch-

Yeah, I'm well used to the variations in oil pressures for all kinds of engines. As long as I know what to expect (starting with the excellent pattern you provided!) and through observing how it works on my low-mileage example, I promise I won't stroke out the first time I see it vary all over the place.

Also, if you could provide me with the make and model of a nice compact gauge for a good price, or even just where you bought it, I'd appreciate it.

I've got Valvoline semi-synthetic 10W-40 in mine right now, which is what I've been using in my Gold Wing.for years with great success.

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Revisiting Oil Pressure Gauges 2 weeks 3 days ago #27838

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Nice to hear someone got something from my comments. You made an important observation. Gauge readings will vary between engines and to some degree the instrument, itself. Establish the numbers for your engine and use this as the reference.
This should point you in the correct direction. The eBay link from my purchase doesn't seem to work. There are other options but I have found these to be reliable, so far.

Marshall-Gauge-0-100-psi-Fuel-Pressure-Oil-Pressure-White-1-5-Diameter-Liquid
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !
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Last edit: by scotch.
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