Why the topic? We need to get back to basics. One of the most common problems associated with operating older equipment is that we somehow manage to find a problem and then come up with a cure to "overcome" the problem when what we really need to do is get back to basics and understand the problem and "fix" the problem. I can't count how many times I've read about fuel flow issues (or not) and what our members have done to "fix" the problem, so let's go "back to basics"
Brake Specific Fuel Consumption is a theoretical calculation which states that for a normally aspirated engine the amount of fuel required to produce 1 horsepower per hour equals .5 pounds of fuel per hour. Kawasaki advertises the output of the KZ1300 as 120 hp so in theory the fuel flow rate to sustain 120 HP for 1 hour would be .5 lbs./hr X 120 hp = 60 pounds of fuel. In theory, the fuel flow rate needs to be equal to or greater than 60 pounds of fuel /hour.
Gasoline weighs somewhere between 5.8 to 6.3 lbs per U.S. gallon depending apon the blend of the fuel including ethanol which is alcohol so for sake of argument let's say gasoline weighs 6 lbs. / U.S. gallon. If we need to be able to sustain a horsepower rate of 120 HP maximum then we need to be able to flow 10 U.S. gallons per hour.
Now we need to figure out an amount of fuel we can easily measure to assure ourselves of adequate fuel flow rate. So how about the amount of fuel we could measure in 30 seconds.
30 seconds is 1/120th of an hour.
1 U.S. gallon is 128 fluid ounces. 10 U.S. gallons is 1280 fluid ounces.
Our design fuel flow rate should be 1280 fluid ounces divided by 120 = 10.66 ounces in 30 seconds That's the magic number.
Kawasaki doesn't make any fuel flow rate checks in the service manual and that's an oversight on their part. Without that information how do you know what your system needs to flow so that you're not starving the engine?
So what's in the fuel system to impede the flow of fuel? We have the fuel petcock (both in the on position and reserve position), the fuel line,the fuel filter, the fitting on the carb, the fuel tubes between the carbs and the needles / needle seats. If you were to pull the fuel line off of the fuel feed tube on the carb and measure the fuel flow for 30 seconds, you should measure 10- 1/2 ounces of fuel. You should do this test with the fuel tap in the on position and also in the reserve position. In theory, anything less than 10 ounces in 30 seconds would be inadequate. It could be a blockage in the fuel tap, or swollen fuel lines from ethanol, or a blockage in the fuel filter. By checking the fuel flow at different points along the fuel system, you should be able to "find the problem".
This next test should be done to check the fuel flow rate to each of the carbs. If the total fuel flow rate needs to be 10.66 ounces or more for all 3 carbs then 1/3 of that rate should be flowing to each of the carbs. 1/3 of 10.66 ounces is 3.55 ounces in 30 seconds that's the next magic number. How can we accurately measure this? In theory, the drain screw on each of the carbs should be able to flow more than this but if I were to try and measure this and get less than 3.5 ounces in 30 seconds, then I would pull the float bowls and measure with the bowls off.
Assuming the drain ports on the float bowls will flow more than 3.5 ounces per 30 seconds , this would be my next test. Turn off the fuel petcock and drain 1 of the float bowls. Place your measuring cup under the float bowl drain port and turn on the fuel tap. Measure the amount of fuel collected in 30 seconds. Repeat for each of the carbs and record your measurement. Anything less than 3.5 ounces in 30 seconds is a problem in theory. If the flow rates are less than adequate in the left and centre carb, the problem could be in the connector tubes or the needle/needle seats.
That's the theory. In the beginning when our bikes were new, the fuel system worked. We shouldn't need to put on fuel pumps to "fix the problem" We do need to test fuel flow and be able to rule out issues or "find the problem and fix it" so for those of you having drivability issues , I hope this helps.
KB.
