The Merlin® Gerotor Oil Pump was capable or supplying nearly 1 ½ times the oil volume of the stock Harley® oil pump, and more than 5 times the volume of the return and yet the housing is nearly the same size. Because of our unique gear and housing design (patent pending) the Merlin® pump can be made much smaller than other gerotor pumps. Other gerotor pumps that have been made for big twins were at least twice the size of the original oil pump and nearly twice as expensive. Gerotor pumps are not made like the conventional Harley Davidson pump.

Gerotor pumps have a set of gears similar to the ones shown in the picture shown. The oil is pumped through the cavities between the gears.

The oil in a gerotor oil pump is contained within steel gears and they do not expand like the aluminum housing of the conventional pump. The pump also has a spring-loaded plate in contact with the gear surface that completely seals in the oil pressure. The conventional OEM pump has much looser tolerances that are necessary for the design and as the pump heats up these tolerances get so great that the oil leaks past the parts so pressure and oil volume are lost. Because the tolerances are so tight between the gears this pump would not cavitate until the motor reaches over 14,000 RPM. That RPM is more than twice as high as even racing motors will ever reach.

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