High Volume Oil Pump

Why the H2 Runs Low Pressure

The H2 family carries additional shafts inside the engine to drive and support the supercharger system. Every one of those shafts needs feeding, and each oiling passage bleeds a little pressure out of the system. Add Kawasaki's deliberate choice to run low pressure in the interests of efficiency and emissions compliance, and the result is an engine operating at noticeably lower oil pressure than most comparable performance engines.

Standard figures sit somewhere around 25 to 37 psi depending on variant, measured at 50°C and 4,000 rpm, and can fall to single figures at hot idle.

For a standard motorcycle ridden as Kawasaki intended, that is entirely adequate — it was engineered that way on purpose. The difficulty is that it leaves very little margin, and margin is the first thing to disappear when you change what the engine is being asked to do.

What Changes Under Load

People now routinely extract well beyond stock output from this platform — in some cases more than the factory H2R produced. Bearing loads rise accordingly, while the lubrication system coping with them remains the one designed around a standard road engine.

Connecting rod and main bearing failures attributed to inadequate oil pressure under raised boost and load are a recognised pattern on this platform. It is a predictable consequence rather than a mystery: more load, more heat, thinner oil film, and a pressure figure with no headroom to begin with.

In a car the same reasoning applies with additions. Sustained high output is the norm rather than the exception, and cornering loads act laterally across the engine rather than being cancelled by lean angle. The pump becomes the component every bearing in the engine depends on.

Two Configurations

Which one you need depends entirely on whether the engine still has its original water pump — and that depends on whether you are running a dry sump.

Why the Dry Sump Changes the Answer

On our dry sump conversion, the scavenge pump is positioned where the original water pump sat. That is a deliberate packaging decision — it puts the scavenge stage where it needs to be and keeps the installation compact — but it means the standard mechanical water pump cannot stay.

Cooling instead moves to an electric water pump running under ECU control. In a car that is arguably the better arrangement anyway: coolant flow becomes a mapped function rather than something tied to engine speed, so you get flow at idle when heat soak is worst and no parasitic drag at high rpm. The MBE 9A9 carries a dedicated electric water pump output, so the control is already provided for.

The practical consequence for this product is simple: in that configuration the billet pump body has nowhere to go, so we supply the gerotor gear set on its own. You get the full pressure benefit without buying a housing you would put straight on the shelf.

The electric water pump itself is an open choice. Any suitable unit will do, we are happy to work around whatever you intend to fit, and it does not need to be decided before the dry sump is ordered. If you would rather not source it separately, we can supply one as part of a complete package.

Leaving the Gear Set Out Costs More

Worth stating plainly, because it is counter-intuitive and it comes up.

Our scavenge pump is built around the uprated gear set. Specifying a dry sump without it means the scavenge pump has to be machined as a one-off, and one-off machining on a part of this kind will typically exceed the price of the gear set itself.

So if you are having the dry sump, take the gear set with it. Better oil pressure for less outlay than the alternative — the two decisions are linked, and this is the direction the economics run.

Monitor the Pressure

An oil pressure gauge is strongly recommended on any H2 running raised output, with or without this upgrade. If you are going to the trouble of improving the lubrication system, you want to be able to see it working.

One caveat when you do. Motorsport pressure sensors frequently read apparently low or delayed on this engine, because the available sensor location sits downstream in the oil galleries rather than at the pump outlet. Interpret readings against what is normal for an H2 rather than a figure you would expect elsewhere — otherwise you will chase a fault that is not there. Our H2 engine reference covers this.

Fitting and Timing

Either configuration requires access to the pump, so the sensible moment is while the engine is apart — during a rebuild, or alongside a dry sump conversion. Fitted then, the additional labour is close to nothing.

Tell us which configuration your installation calls for when you enquire. If you are not yet certain whether you are running a dry sump, that is the conversation to have first — it determines this decision and several others.