TOPIC:

Hi, my ol' 1980 KZ1000 A4 starts up with around 6 lbs. oil pressure but after riding a little bit drops to the 0-1 range,sometimes the light comes on.Its 28 years old now so i'm thinking the oil pump just aint its best anymore. Is there a better oil pump to replace it with,? or modifications that can be done to freshen this one back up?
Someone told me to "mill" the oil pump to tighten it up a little.Anyone know about this?? Any suggestions?

Here's what I know:

1) I recently rebuilt my KZ750 with 78k miles. I assumed the oil pump would be worn, so I ordered new rotors.

One of the real experts on the other Kawi forum said that was probably a waste of money because KZ oil pumps don't wear much unless they are really abused with dirty oil.

Well, he was right. I took the pump apart and could not measure ANY wear at any of the critical dimensions which means I didn't need new rotors.

2) As to "milling the pump"... I assume he means grinding the case lip to reduce the side dimension and rotor clearance? I doubt very much it needs it. If the rotors are worn, you can buy new ones.

Chances are, the low pressure is not the pump's fault. But, if it is it should be fairly easy to gauge the rotor clearances and see if it's worn.

steve3408 wrote:

Hi, my ol' 1980 KZ1000 A4 starts up with around 6 lbs. oil pressure but after riding a little bit drops to the 0-1 range,sometimes the light comes on.

Do you mean at idle?

How are you measuring the pressure?

If I recall, the oil warning light should be coming on at pressures under about 8 psi or so. If it actually got down to 1 psi, that light should be on strong.

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?

I don't have a manual covering the 1015cc 1000 motors, but the J motor manual specifies oil pressure at 2.8 PSI at 3000 rpm at 60c

The 900/1000/1100 motors have roller bearing cranks, and you can't have pressure with roller bearings because there is little restriction to flow.

I was going to suggest he try using Castrol 20W50... whatcha think? hehe OIL THREAD ALERT?

wiredgeorge wrote:

I was going to suggest he try using Castrol 20W50... whatcha think?

Couldn't hurt. I'm still trying to figure out how an oil system can shoot oil up into the overhead cams with only 2.8 psi of pressure at the outlet of the pump...?

I would have thought they would need to put restrictor orifices to keep the system pressure up.

bountyhunter wrote:

wiredgeorge wrote:

I was going to suggest he try using Castrol 20W50... whatcha think?

Couldn't hurt. I'm still trying to figure out how an oil system can shoot oil up into the overhead cams with only 2.8 psi of pressure at the outlet of the pump...?

I would have thought they would need to put restrictor orifices to keep the system pressure up.

The restrictors in the plain bearing motors are there to keep from flooding the overhead with oil, not to keep the pressure up, although they do have some affect on that.

I know you have seen ball and roller bearings, see any way of restricting flow through one of those? Actually, no engine designer cares about oil pressure, it's all about flow, pressure is merely an indication of the amount of resistance to flow.

steell wrote:

bountyhunter wrote:

wiredgeorge wrote:

I was going to suggest he try using Castrol 20W50... whatcha think?

Couldn't hurt. I'm still trying to figure out how an oil system can shoot oil up into the overhead cams with only 2.8 psi of pressure at the outlet of the pump...?

I would have thought they would need to put restrictor orifices to keep the system pressure up.

The restrictors in the plain bearing motors are there to keep from flooding the overhead with oil, not to keep the pressure up, although they do have some affect on that.

I know you have seen ball and roller bearings, see any way of restricting flow through one of those? Actually, no engine designer cares about oil pressure, it's all about flow, pressure is merely an indication of the amount of resistance to flow.

But to get an even distribution of a fluid in a system with multiple outlets at different distances away or different "resistances to flow", you must have some back pressure. It's like the watering hose that is plugged at one end and has about 20 small holes in it that all spout about the same amount of water all the way down the hose. Drill a bigger hole near the faucet end and nearly all the water will come out that hole. Yopu can add lots of big holes and you won't get an even distribution because there is too little back pressure.

The main bearings are down right by the pump. If there is no restriction on the feed from the pump outlet to them, there would be no way to get enough pressure to force the oil up to the top... the lion's share of the oil would just be dumping into the bearings and falling back to the pan. They must be doing something to get enough pressure to make the oil go uphill.

steell wrote:

I know you have seen ball and roller bearings, see any way of restricting flow through one of those?

Maybe put a restrictor valve in the passage from the pump outlet that feeds the bearings.

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?
You'd love the pressure readings in a hydraulic system, 3000 psi or so

The 900/1000/1100 motors were designed with the roller bearings in mind, and the oiling system was sized to provide sufficient flow to the bearings on the crank while leaving enough flow for the cam bearings.

The main bearings are down right by the pump. If there is no restriction on the feed from the pump outlet to them, there would be no way to get enough pressure to force the oil up to the top... the lion's share of the oil would just be dumping into the bearings and falling back to the pan. They must be doing something to get enough pressure to make the oil go uphill.

Obviously 2.8 PSI is enough, it works

The lions share of oil does lubricate the main and rod bearings and dump back into the pan in every motor, that's why the passage feeding those bearings is the largest passage in the motor. The top end doesn't require a lot of flow to lubricate the cam bearings, and excessive oil in the overhead floods the valve seals and increases oil consumption. I have actually seen engines that had plugged drain passages that were burning oil and blew the valve cover gaskets due to pressure build up in the overhead.

I have also seen motors blow off the oil pan and valve covers due to a leaking mechanical fuel pump dumping gas in the crankcase and the gas igniting. Another real good reason to change the oil when the carbs flood and dump gas in the oil

I wonder with the specs on the oil pressure is at such a low oil temp (160*).
The "normal" oil temp must be more like 210*/230*

I have a Z1b with a cooler and an oil pressure gauge and when starting the engine from cold (with Kendall 20/50) the pressure is about 13psi/14psi at idle
That also must be the setting of the pressure relief valve since revving the engine do not increase the psi.
I need about 7 to 10 miles for the oil pressure to stabilize at 4.5 to 5 psi at cruising speed (5000 rpms)and it will stay at this psi level even in 100* + weather.