Mikuni fuel pump, Mikuni fuel pump parts, Rotax single fuel pumps, Rotax dual fuel pumps Rotax fuel pump parts.

 Light Sport & Ultralight Aircraft Parts Information


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Mikuni fuel pumps

The Mikuni fuel pump is the primary pump used in the ultralight industry,  When mounting the pump make sure that it is no more than 11 inches away from the impulse outlet on the engine. Make sure that it is mounted away from any heat source, and that it is positioned so that the vent on the pump face is facing down.

The vacuum line used to connect the pump to the engine impulse outlet is of a much thicker wall thickness than regular gas line, and is not effected by heat. The gas line and vacuum lines are generally exposed to sunlight in most older configuration of ultralights and it is suggested that they be checked on a regular basis for cracks, discolouring, or UV deterioration. All lines should be carefully clamped, with clamps that do not pinch the line.

The fuel system should have some kind of a water trap, this can be as simple as a loop in the line used to join the two gas tank halves together on a root tube mounted tank, a proper inline filter with a drain cock, or a pickup line located an inch from the bottom of the tank. tank.

During initial installation of the tank it should be inspected to make sure that no plastic is present, inside, from the drilling of holes, or from the manufacturing process. More than one pilot has had to land with an engine out only to discover plastic lodged in his fuel pump.

A fuel filter should be installed in the fuel system prior to the pump to prevent any foreign material from entering it. If for any reason the filter is removed and is going to be reused make sure that the direction of flow is the same as when it was removed. Several pilot has reported reinstalling their fuel filter backwards, depositing all the foreign material collected directly into their pump and carburetor. Most quality filters have arrows showing the direction of fuel flow.

When considering fuel tank location, try to make it as close to the engine as possible with the least amount of vertical draw. Although the Mikuni pump has been known to draw fuel vertically over 4 feet the recommended distance is only 18 to 24".

Make sure all tanks are properly vented. Many ultralight manufacturers use a standard marine fuel tank, with a vent on the handle that can be screwed in to seal for transportation.

The problem here is that the vent can vibrate closed, or can be inadvertently left closed. This allows the engine to run for a short period of time before it runs out of gas, just about the time your 50 feet in the air.

If you have one of these tanks a solution is to drill a small hole in the handle, at its highest point. Another problem with some of these tanks is that they have a steel check valve located in the tank fuel outlet, in some cases this ball is to heavy for the Mikuni fuel pump to lift completely, causing a fuel starvation problem.

Make as few restriction in your fuel system as possible.

Some pilots have installed electric fuel pumps into their systems, in addition to the Mikuni pump. There are several potential problems with this.

First the electric pump is capable of producing considerably more pressure than what the fuel system is set up for. Secondly when the pump is turned off it is an added restriction.

Single Mikuni fuel pump parts
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Dual Mikuni fuel pump parts

Dual Bing Carburetor primer installation diagram and primer parts

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