Fuel Fuji Carbureted

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Courtesy santacruz/ph2ocraft

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bd

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dorf

The Why and the How of the Polaris Mikuni 3 Output Fuel Pump

From :Performance Motor Sports, Fort Wayne , Indiania- 4/6/04


I will try to tell you in short terms the problem with the stock pump, and fuel line routing. If you look at the stock pump it is a single outlet pump that feeds out to the end of the carb rack. The fuel under pressure from the pump goes into the first carb body and fill the chamber then floes out of the chamber to fill the center carb and at the same time keeping the first carb chamber full. It now fills the second chamber and then flows out to the front carb and tries to fill it. Remember while its trying to fill the front carb it is trying to maintain the fuel level in the other 2 carb chambers. When Polaris first designed this the stock pump was adequate when the pumps were at new condition. Polaris started having piston problems in a little over 2 years from the dates of the manufacture of the watercraft, or once the fuel pumps started to loose some of there efficiency.
In 1996 we worked with the Polaris factory to diagnose the problem. What we found was the fuel pressure and volume had changed from when the pumps were new. That is why they changed the pumps on the 780 SLX's. A bulletin was sent out to all Polaris Dealers to redo the Fuel line routing in an attempt to eliminate the problem. That worked until the pumps continued to loose efficiency and then the piston problems came back.

SO that's where we came in and came up with the triple outlet pump and feeding each carb individually. Regardless as all the People that think they know on the internet, if you had a new single pump and had the correct fuel line routing they will work fine, but the issue us not knowing how soon the pump looses it effect, and its not worth taking the chance. We use to sell just the pump, but then people would not hook them up correctly, use the wrong size fuel line, and we spent countless hours on the phone answering questions. We decided that we would only sell the complete kit. It comes with the new pump ($30) Correct size actual fuel line(Not from the hardware store) tywraps and plugs to redo the fuel routing, and detailed pictured instructions on how to install it. The timeframe to install it is under 1 hour.
There is no diagnoses for it, but the facts are that if you don't redo it you stand a VERY good chance that you will burn a piston, but nobody can tell you when. This change eliminates the fuel volume as a factor and is alot less expensive then pistons.

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These are the MBZ caps used for covering the oil injection nipples when the oil injection system is removed.

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Mikuni Manual

[CrazyA]

Richie had a 750 starving for fuel. Funny thing is, the pump, carbs, fuel lines (etc.) all appeared to be sweet. Sooooo, he went inside the tank.

Just a reminder to check your tank pickup(s) whatever style they may be, no matter how cherry the boat looks.



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Left photo shows restrictor location for 38mm Mikuni carbs.
Right photo shows high elevation jetting.
Lower photo shows fuel venting for 92-93 Fuji.