Special Tools needed :

• Factory Pro Float bowl gauge (available on our website click here) or the butt end or depth gauge on set of calipers will work as well but with more difficulty.
• Small screwdriver 3/16 flat blade
• Small length of fuel line ( 3 inches will do)
  
  
  
  

Why is the float bowl adjustment is necessary? I'll start by addressing the common misconception, that fuel flow in a carburetor is regulated strictly by the size of the carburetor jets (or the jet orifices to be precise). In fact, it is the jets size AND pressure (or suction) that regulates fuel flow through the jets at any given time. Take an air hose for example. Turn the regulator on a small amount and the air flows at a slow rate. Turn it on more and the air flows at a faster rate. In both instances the diameter of the garden hose did not change.

What does this have to do with your float level? Marc Salisberg at Factory Pro Tuning puts this in these simple terms : "picture a person sucking on a straw in a can of soda. Now picture another person sucking on a straw in the same can of soda but with a straw as high as a two story building. The person sucking on the long straw with require much more suction to get the soda up to his mouth." Now to clarify, the key here is the distance to the level of the soda in the can. Now picture the same scenario but instead with the carburetor jets instead of the straws. It is easy to see that the fuel flow rate can be greatly controlled with the adjustment of your float bowl thereby the level of fuel in the fuel reserve (float bowl). The higher the float level the more fuel flow at a given suction. The lower the float level the less fuel flows at that same suction.

There are two measurements associated with float adjustment

1. Float Level which is the measurement of the float from the float bowl seam (or hash mark on some bikes to the top of the float)
2. Fuel Level which is the measurement of how high the fuel level is in the float bowl.

The most common method for float adjustment is to adjust the  fuel level with a piece of  clear tubing connected to the float bowl drain  and held to the side of the carburetor. When the drain valve and the level of fuel in the hose shows the same as the level in the float bowl. The problem is that adjustment means removing the carburetor for the adjustment and reinstalling it to see the results. Trial an error if you will, which means removing and installing the carburetors several times to get the desired results. A very time consuming  way to make this precise adjustment.

So, it there an easier way??

 In this article we are using Factory Pro's nifty float bowl gauge to aid in this process. You can also use a set of calipers but this is more difficult and less accurate. The following is a step by step guide on adjusting you float Bowl on your CV Carburetor using this gauge. If you are using a caliper you'll need to improvise but you'll get the idea.

1. Remove your carburetor or carburetors from the bike and remove your float bowl cover. Place a clean rag or newsprint on a clean section of your bench with plenty of light. Get seated if possible. Being comfortable will greatly enhance your patience and accuracy here.
   
   
2. One of the tricky aspects to determine is the correct position of the float bowl for this measurement. We are setting this particular carburetor at 14 mm for the Predator Pro Kit. Check with your jet kit supplier for the correct specification's. Lay the carburetor on its side and practice tipping it very slowly (as slow as possible) so that the float is all the way out of the carburetor, then all the way in. You'll notice that there are actually three "catch" points.

   
   A. All the way out of the carburetor body as the carburetor is tipped to its normal position.

     RoadStar carb shown for illustration purposes only
   
   B. A very subtle mid point where the bowl catches as the carburetor just starts to turn from being on its side to upside down position (this is where you measure from)

   
   
   C. And finally, all the way into the carb body as you turn the carb upside down.

   
   
   

3. MAX-TIP: Now if you do not feel comfortable with finding the exact sweet spot in the middle, this simple trick will help you out. Take a short piece of tubing and attach it to the fuel inlet on the carburetor. Next gently blow in to the hose as you repeat the procedure in number 2. When you find the spot where the line becomes plugged, that is the point you are looking for. Be careful when measuring not to go past that point. The midpoint and the point where the air just stops to flow will correspond. This is your measuring point. You want to use the point on the float bowls that is furthest from the gasket area (the highpoint if you will) Since the floats have two pontoons and a curved base you'll need to locate this point by sliding the gage along each pontoon.
    
   
4. Now that you have found the location where you need to take your measurement, you can prepare the float gauge for action. There are three parts to this tool. the two legs that will straddle the float bowl and the measuring arm that will take the actual measurement. The legs must be spread the correct distance to allow you to rest them neatly on the float bowl gasket surface on the carb body. Be careful not to interfere or push on the float bowl while measuring.
   
   
   
   
5. MAX-TIP: When measuring I like to set the gauge a tad higher than I am shooting for. I then look at the light between the measuring are and the float pontoon. This way I know for sure I am not pushing the float in while measuring. When I feel I am right on I set the gauge to the exact point and give it another quick check.
    
   
6. As mentioned before, I am shooting for a float height of 14 mm for this adjustment. The float should be set at just under 12 from the factory. I need to bend the metal tab which controls the fuel metering as the float moves. Remember with floats, everything is opposite. So by going from 12mm to 14mm I am actually lowering the fuel level in my float bowl. This will lean up my lower end  a bit and should give me a crisper throttle response. I should also see an increasing gas mileage, which is always a good thing these days.
   
   
7. Locate the tab on the float bowl right at the hinge. Be very gentle here and do not brake this tab or the float bowl. While holding the float open carefully use the small screwdriver to bend this tab to the correct position. Now if you are increasing from 12 to 14 mm as in this case you would bend the tab inward towards the carb body. If you needed to reduce the measurement say to 13 then you would bend the tab outward. Bend the tab very slightly and then check the easement again. You are in for some trial and error here to find the correct point. Just take your time and breath.
   
   
   
8. MAX-TIP: with a small screwdriver use the hinge pin as a lever point to bed the tad. A gentle twist on the blade will be enough to bend the tab in the preferred direction.

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