Dynojet carburation kit for Harley-Davidson

More joy for carburetor
In a Previous article There was talk of the need to adapt the carburation or injection if the escapes or the air filter were changed, or if any other change was made that affected volumetric yield (the amount of air that comes in and that comes out) of the engine.

El carburador CV
Well, I will explain how to make this adjustment in the Keihin CV carburetor, which equips all HD (and many other motorcycles) as standard from 1989 to 2006. This is a “constant emptiness” carburetor, which works very well In street motorcycles and yet it is one of the first pieces that many owners throw in the garbage cube as soon as they want un motor de hasta 88ci (1450cc), para uso “de calle”, un carburador más grande no va a ser siempre mejor. La razón es que si el carburador es demasiado grande perderemos respuesta en bajas y medias RPM, donde más se utiliza el motor. If we are not going to compete and our cuturies and camshafts are not very aggressive, the almost 40mm of Keihin CV venturí are enough to make our V-Twin happy, yes, after preparing it a bit.
Apart from the increase in air flow after changing exhausts or filter, we must also consider that these carburetors are not optimally configured because the pollutant emission regulations have to be complied with (therefore it is under the responsibility of the owner to modify the vehicle for use in public roads). The carburetors are prepared with excessively poor mixtures and sealed regulation screws, and even the air filter also functions as a noise silencer, so it is highly recommended to replace it with a high -performance filter element, type K & n or similar.

Hands to work
We will turn our boring carburetor into a more cheerful element by installing a Dynojet Kit.

I have chosen this kit because it adapts specifically to each year and motorcycle model, but it could also have installed any similar kit of other manufacturers (Yost, Screamin ’Eagle, Cycle Pro, Slinger ...). The kit comes with 2 drills, adjustable needle, diffusers (gum) of various sizes, emulsion tube and even a sticker that although it will not cause the motorcycle to run more cool in the lid of our toolbox. In the photo I have also added a low diffuser (Slow-Speed ​​Jet) and a new admission board for the carburetor.
The first thing we have to do is extract the motorcycle carburetor following the instructions of the service manual. Then we drill the sealed cap to access the mixture adjustment screw to the idle.

Be very careful, because we can forever damage the screw below. You just have to make a small hole in the cap, after which we will introduce the extraction screw and stretch with some pliers to remove the cap (we discard the cap and the extraction screw). Then we screwed very delicately the regulation screw until we settle and take it 3 laps, this will allow us to start the motorcycle to perform the carburation adjustment.
We proceed to unscrew the main diffuser and the emulsion tube, and replace them with those that come in the kit. We choose the recommended diffuser number in the manufacturer's instructions, depending on whether the motorcycle is totally original, with high -performance filter or exhausts, or with high performance camshaft.

In the image above we can see this screw and the diffusers already replaced. We install the tapa from the tap and disassemble the upper carburetor lid, take out the spring and vacuum piston. With the drill #29 supplied in the kit we proceed to enlarge the piston hole (eye, not to confuse with the central hole of the needle). This operation together with the change by a lighter dock will get a faster carburetor response.

We return to ride everything again, taking into account replace the dock and needle with the new elements. In the needle we will place a clip following the manufacturer's instructions and on top of this 3 washers.

When we close the lid we do it with caution so that the Board settles well. Tip: Before tightening the screws we hold the lid with the fingers and climb and lower the piston, to see if the void slows it slightly.

We are going to "carbure" ...
Once the carburetor and the filter start the engine and let the operating temperature reach. We adjust the slowdown (not too low) and slowly screw the mixing regulation screw until the engine begins to fail. We take note of this position and slowly unscrew the screw until the engine begins to fail again, and take note of the new position. The ideal mixture screw adjustment is exactly half the way between these 2 positions. Tip: If this position requires disregarding the mixing screw more than 3 and a half laps from its fully closed position we may have a diffuser (slow-speed jet) too small for our engine. For Sportster and Evolution I recommend a # 45, and for Twincam 88 I recommend a # 48. We adjust the idle and voila again.
If you have followed the instructions correctly right now you will be rolling to the wind, with a more powerful engine and better acceleration. Enjoy it!

Frank Burguera

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