Article from Dave Leonard of Precision Cycle Works

Most of us have already installed a jet kit on our motorcycle with often little or no idea of how they work or why the carburetor manufacturers haven’t simply incorporated these rather simple improvements in the first place. Now, another product comes along making the whole thing even more confusing. It’s actually rather understandable, however, once you know how all this stuff works and how these products evolved.

First, lets briefly cover what the jet kit does. The motorcycle / carburetor manufacturers must comply with Federal emissions regulations and similar mandates around the world. The effect of all this regulation is a slight reduction in performance. The jet kit makers, however, are not subject to any of this and can focus their attention on getting the best fuel flow characteristics without regard for any outside authorities. Who knows what future government interventions may be applied, but for now, the jet kits provides a means to make an improvement, but there are some problems.

While the jet kit satisfies the fuel requirements, there is another product that addresses carburetor efficiency in a very different way. Its manufacturer discovered that the air jets were not particularly satisfactory in doing their job. The function of these is to better atomize (convert into a gaseous state) the fuel / air mixture rather than allow any portion of the fuel, being drawn up out of the float bowl, to simply sheet along the floor of the carburetor and trickle into the combustion chamber in a liquid state. These jets help to excite the fuel as it come up from the float bowls and better atomize the mixture as it enters the carburetor’s bore. The problem results from the less than an ideal situation at the jet inlets. The far larger quantities of air entering the carbs cause considerable disruption to the small amounts of air entering the air jets (just below the carb bores).

The Flo-Commander provides a set of fittings to replace or press over the main jets, a set of tubes to connect the new fittings to a central control valve to adjust the air volumes to the proper level, and all the necessary hardware to install. I’ve installed over one hundred of them and I’ve installed even more jet kits over the years. Jet kits are nice, and they nearly always make some improvement, however, the Flo-Commander, in most applications delivers a more noticeable correction.

1. Here are some of the more specific advantages.

1-The Flo-Commander (FC) can be used with one, two, three, or four cylinder engines. Part of its US patent deals with its ability to precisely and equally distribute air regardless of the number of cylinders.

2-Since the air jet (air bleed) fittings on multi-carburetor engines are connected to a common inlet (the Flo-Commander control valve), the individual carburetors are far better synchronized than would otherwise be possible.

3-Over-carbureted engines and especially the big V-twin motors tend to have the greatest need for keeping the fuel sufficiently atomized. Here again, the typical jet kit can’t do much about this problem.

4-The inlets to the air jets are re-directed to a more friendly location (away from the carburetor inlet/s) eliminating the disruption problem, mentioned in the text above.

5-The lengths of tubing (connecting the air jets to the control valve) provides a greater degree of inducted airflow. As the airflows are ‘already flowing’ through the length of tubing into the air jet inlets, the system’s performance is further enhanced.

6-The FC control valve has an airflow adjustment control knob providing easy adjustment of fuel/air mixture often making jetting or needle adjustment unnecessary.

7-In most applications, the installer won’t need to remove the carburetors at all. Just a few modifications to the airbox, install the adapters and you’re all set.

8-I have often seen the consequences of ‘going into the carbs’ by some pretty good mechanics. Unfortunately there are many opportunities to ‘mess things up’ when servicing a set of modern day carburetors. Most everyone ‘thinks’ they know what there’re doing here, but we often have to straighten out problems caused by well-meaning mechanics or a ‘knowledgeable’ bike owner.

9-The system provides easy adjustment for seasonal or altitude changes. This will make tuning much easier and again prevent even more fiddling with the delicate carburetor systems.

10-It simplifies routine carburetor adjustments. The automatic synchronization and far more stable manometer operation make diagnostic and normal adjustment efforts more straightforward.

11-If an ‘across the board’ fuel / air ratio change is needed on a conventional carb setup, the main (fuel) jets, needle position, & pilot jets, etc, may all need some tweaking. All of this can be handled much more quickly with the Flo-Commander and with only the twist of an indexed control knob. Pretty neat!

12-If all of this isn’t nifty enough for some folks, Performance Design (makers of the Flo-Commander) now offer a remote control system to the basic FC valve often saving the owner or the mechanic the need to remove components to access the valve itself. This a tremendous advantage to the tuner or Dyno specialist as well as the racer’s need to ‘fine tune’ to track conditions.

All of the products I’ve seen from Performance Design are beautifully engineered with great attention to detail. The manufacturer obviously spent endless hours performing the necessary R&D and getting everything just right before going into production. Even the instructions are taken to a much higher level with top quality illustrations and in-depth step-by-step procedures.

After many years of installing jet kits my customers nearly always express some degree of satisfaction with statements such as “Yea, I think it’s a little better” or “The flat spot’s pretty much gone now”. Not bad, but nothing to get all excited about. With the Flo-Commander, however, it’s a very different thing. My customers typically remark something like “Wow, what a difference” or “It’s like a totally different motorcycle” or “The power delivery’s much better, but why is it so much smoother?”. I continue to install plenty of jet kits, but I prefer to begin with the Flo-Commander. I like happy customers, and that’s what this product is all about.