Keihin Carburetor Adapter Overview  

There are 3 body styles to the Keihin FCR:

1.      Keihin Slant FCR

2.    Keihin MX FCR with removable air boot.  This is most commonly adapted to the DRZ400.  The reference “air boot” is located on the air box side of the carb.

3.      Keihin MX FCR without removable air boot.  Adapter is readily available.  Allgeyer Performance Adapters are used with this carburetor style.  Notice there is no bolt on plastic adapter on the air box side of the carb. 

These body styles can have 3 option packages.

1.                Choke

2.                Choke and hot start

3.                Choke, hot start, and throttle position sensor (TPS)

When trying to find the appropriate FCR you need to inspect for port size.  When you hear about 37, 38, 39 or 41mm carbs the referenced measurement is the throat size as measured from the position of the flat slide.  See the picture below, this is a 39mm carb.  39mm and 41mm carbs are most commonly adapted to the DRZ.  The smaller the bore the more “torquey” the motor will be.  Some have used 37 or 38mm carbs and had success. If you have a DRZ400, any replacement Keihin will perform better than the stock Mikumi.

From our research 39mm carbs were available from the factory on some of these models:

• 2003-2007 YZ450F

• 2000-2009 KTM 525 XC four wheeler

• KTM RFS 4 stroke motorcycles 450 and 525

• CRF450X

Keihin FCRs of all sizes (37-41mm) come standard on all 250 & 450 Yamaha, Honda, Suzuki, Kawasaki, and KTM dirt bikes.  These motorcycles are the best source of donor carburetors and can be obtained at a low cost. 

Allgeyer Performance Products's adapters can be coupled to any FCR without the removable air boot, regardless of the bore size.  APP-1001-2 (Suzuki DRZ400), APP-1002-2 (Suzuki DR650), APP-1003-1 (Honda XR650, XR650L, Husaberg Carb), APP-1003-2 (Honda TRX450), APP-1003-3 (Honda 400EX), APP-1005-1 (“mini” FCR from Honda CRF150R), APP-1004-1 (custom applications).

November 26, 2018