Keihin FCR Carburetor Jetting
In the photos below, I am installing a DynoJet #3111 carburetor jetting kit. This procedure involves changing the needle clip setting and main jet. The DynoJet kit installation is slightly different from stock jets, but I have explained the differences where they occur.
To access the carburetor you must first remove the seat and tank. Next, loosen the hose clamps holding the rubber air boots on both sides of the carburetor. This will allow you to rotate the carburetor slightly to the side exposing the top cover.
Removing the top cover will expose the throttle valve (or slide).
On the top of the throttle valve is the needle set screw which is removed with a hex wrench. The needle set screw is already removed in the photo below, but you can see it in the later photo showing the removed needle.
Once the needle set screw is removed, the top of the needle and needle clip are visible.
Gently grasp the needle with pointed pliers and lift up to remove.
Here is the needle set screw and needle with clip installed as removed from the carburetor. Some carburetors may include a spring or additional washers under the needle set screw—if these exist, pay careful attention to their order!
The DynoJet kit includes a spacer washer that is added to the needle above the clip. Note that the clip has been moved down one position per the DynoJet instructions. Be careful when moving the clip position. The clip may spring off and be lost easily!
After reassembling the needle and top cover, rotate the carburetor so that the float bowl drain bolt is accessible. To the front of the drain bolt the pilot screw is visible in its recess.
Use a 14 mm wrench to remove the drain bolt.
The main jet is now exposed.
Remove the main jet with a 6 mm wrench.
A bottom view shows the main jet removed. This exposes the main nozzle.
If you are installing the DynoJet kit you will need to install DynoJet's main jet adaptor.
You can utilize a small socket for installation of DynoJet's main jet adaptor or Keihin jets. DynoJet's main jets are round and require a screwdriver for installation.
Here is a photo of the original 0.142 inch main jet (left) next to DynoJet's main jet adapter and main jet (right). Make sure to select the appropriate main jet size for your application. Notice the dirt in the drain bolt. Clean this up before reassembly.
Dynojet 0.140 inch main jet installed.
Reinstall the drain bolt on the float bowl and rotate the carburetor back to its normal position. Most importantly, be sure to re-tighten the intake air boot hose clamps or your bike will run lean or not at all!