The GT750 oil pump is an interesting and strange device that appears to defy logic and yet is remarkably simple.

The pump consists of three major assemblies seen in the picture above. 

Top Cover

At the top is an aluminium cover which contains the bleed screw, oil intake and actuator arm. the actuator arm is moved either by a throttle cable (early models) or a by a linkage rod (CV carbs).

As the throttle is opened, the arm is "pulled" which makes it rotate in a counter clockwise direction. The arm roates on a steel shaft which is ground into an eccentric in the center.

Pump Body

The pump body contains the passageways through which oil is pumped in measured amounts through to six outlets  - three for the intake ports and three to the crankshaft main bearings.

Pump Valve

The third sub assembly is the pump valve as it's called by Suzuki. It's a hardened ground steel cylinder containing six ports or passageways and looks much like the revolver of an old six gun. Into two of those chambers are pistons or plungers in Suzuki nomenclature.

The top of the pump valve is ground into face cam with two flat lobes and in the center at the top is a guide pin that locates the top of the pump valve into the actuating shaft in the top cover.

J/K 72-73 pumps

Early model pumps contained three plungers rather than the two in later pump assemblies. the additional plunger was for suction, to pull oil from the oil tank.  that was found to be unnecessary and in fact all oil pumps are capable of collapsing the oil tank if the breather is blocked.

1974 L model pump uses a hardened pin in the top cover 

1976 A model pump dispenses with the pin and the valve body face cam acts upon the actuator shaft

The Pump Valve on the left is visibly lower than the 76 on the right. The face can rubs on that hardened pin, whereas in the taller 76, the pump valve face cam rides directly on the actuator shaft

How does it work?

The pump is driven through a train of gears at 1 revolution per 62 engine revolutions. As it the plungers on springs in the valve body cause the valve body to press upwards against the top cover. As the valve body rotates, the face cam contacts the hardened pin in the top cover and that forces the valve body downwards expelling oil from a port in teh lower face.

When the as throttle is opened, the actuating arm is rotated which allows the valve body to rise higher and creates a longer stroke and more oil is expelled .