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Fuel Delivery Issues 3 years 3 months ago #28668

  • dcarver220b
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Kawboy wrote: It's good to do the math so you fully appreciate what would happen when a fuel filter gets partially plugged.
Bottom line here for me is that this set up is not much different than a push lawn mower. The tank outlet is a few inches above the inlet to the carb and we seldom have fuel delivery issues with our lawn mowers right? The main difference here is that we are trying to feed 3 - 2 barrels carbs hungry for 24 times the amount of fuel of our lawnmower through the same size hose with the same head pressure. ( for the purists, assuming the lawnmower is 5 hp and the KZ1300 is 120 hp)
One thing that could plague a person without the knowledge or attention to detail could be if the fuel line rises above the bottom edge of the tank in vertical height. If you were near empty and went down a hill, the tank outlet could be above the fuel level and allow air in to the fuel line. That air bubble could effectively stop the fuel flow. Without enough pressure to push the fuel up and over the hump in the fuel line, fuel will not flow.
I'm sure all of us at some point in time got stuck for fuel and was forced to syphon fuel from a car gas tank with a piece of garden hose and we all know that if the hose in the tank isn't kept bellow the fuel level, you lose the syphoning effect and the fuel will not flow over the hump in the hose at the outlet of the tank. (God I can taste the gasoline right now !@#@!)
There are times when it's possible to get an air bubble in the fuel line and as long as the fuel line has a positive rise to the tank, the air bubble(s) will find it's way back in to the tank. If the fuel line has a solid column of fuel and no air bubbles, literally all the fuel in the tank will find it's way to the carb due to the syphoning effect but that's impossible because the bottom of the tank is relatively flat and at some point the tank outlet will eventually find itself above the fuel level and air ingress is inevitable.
That's my opinion for what it's worth.


Interesting perspectives. I'm not smart enough to calculate available head pressure vs flow rate as contrasted to restrictions... Guess I should have studied mechanical engineering, LOL.

Me thinks the final, real world test is simple.. run the tank to reserve, activate reserve, see how much farther you can run, then inspect the tank for remaining fuel.. if empty, great job! If not, well, now you know, LOL.

My question to the community would be this: Have you ever proven you can run the tank to 'dry', empty condition, no fuel remaining? I can't say I have.. back in the day an aftermarket company make an aux tank that fitted, sat on top of, the the main tank. It was plastic, with rubber mat between tank paint and tank underbelly. It was horrible. Leaked, slid off, a disaster!

KB, regarding siphoning... a wonderful story of being on an FJR ride with a very fast and competent HD rider. I could not believe the mpg range he was getting, as I was already deep into my 4.1 auxiliary reserve gas tank... then he sputtered to a stop. I said he could have some of my fuel, but he would have to suck the hose. His first suck wasn't enough to get the fuel to flow. So he sucked, hard, immediately, a second time, and got a mouthful of gas.. LOL. I told him he was obviously not a true gasoline thief... as we all know, if you don't get fuel to flow the first suck, pressurize the line to clear the fuel then suck again!

Test hit tomorrow...

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