Keihin carburetors have long been considered some of the finest carburetors in the world.  Now, Keihin has developed an FCR carburetor for the ultimate off road performance upgrade.  The FCR-MX carburetor has been specially designed with the needs of the off road rider in mind.  Following are some of the new features that take motocross and ATV performance to the next level:

• Roller slides for ultra smooth throttle action
• Adjustable accelerator pump
  
• Throttle cable enclosure
• High capacity float chamber
• Float chamber baffle for rough terrain
• Over-flow drain and joint tube
• Quad float bowl vents
• Float drain plug for quick access to main jet
  
• Optional hot re-start circuit
• Optional air cut-off valve
• Optional TPS sensor
• All carbs include choke circuit

This Keihin FCR-MX carburetor kit will give you a serious power increase along with the best throttle response available.  Roller slides provide ultra smooth throttle action and the adjustable accelerator pump provides hesitation free acceleration.  FCR-MX37, FCR-MX39, and FCR-MX41 carburetors are available.  The 37mm carburetors are recommended for 250cc-375cc, the 39mm carbs are recommended for 350cc-500cc, and the 41mm carbs are recommended for 450cc and larger.  Within any particular application selecting a smaller bore size will provide a slightly higher intake velocity producing more torque and mid-range.  The larger bore size will flow better at higher RPM's and thus produce more horsepower at the sacrifice of some torque down low. 

Options include TPS, air cut-off valve, and hot start  circuit.  The built in TPS sensor allows the motorcycle's engine controller unit to utilize the throttle position when calculating the ignition mapping.  Not mandatory but useful.  The air cut-off valve temporarily closes the slow air circuit in the carburetor to create an instantly rich condition.  This helps to control the popping and backfiring common when decelerating from a high RPM.  With some aftermarket exhaust systems some popping or backfiring is almost always present during high RPM deceleration.  The hot start circuit floods the carburetor with fresh air in the event of a hot re-start problem or flooding after tipping the bike over.

No matter which carburetor you select it will come pre-jetted for immediate installation, see jetting specs below.  Tuning and performance specs have been developed for various models over the years to suit a wide variety of conditions, however some tuning will more than likely be required to attain the desired combination of performance, fuel mileage, and drivability.  Extra main jets are available for tuning and genuine Keihin parts are recommended.  Alternatively these carburetors can be calibrated to your own specifications for almost any application.  Please inquire for pricing and options.

Additional genuine Keihin parts and accessories are always available at low prices.  We also carry the Factory R&D air/fuel screw extension, the R&D Racing flex-jet remote fuel screw, the R&D racing power pump, and the R&D racing power bowl.  In addition, the Tokyomods fuel screw, billet hot start nut, billet drain plug, and a lower tension throttle spring are also available to accessorize this carburetor to your preference.

Please feel free to contact us with any additional questions or requests, we are available by direct line, IM, or email.  We are available for tuning and setup questions as well as continuing product support after the sale.