Mikuni Carburetor: History, VM & BS Models for Motorcycles

History

Mikuni Corporation was established in 1911 in Japan, initially manufacturing carbide lamps. By the 1950s, Mikuni transitioned to producing automotive and motorcycle carburetors. Today, Mikuni is one of the world's leading carburetor manufacturers, supplying Yamaha, Suzuki, Kawasaki, and many other motorcycle OEMs globally.

Key Carburetor Series

VM Series (Slide Valve) The VM (Variable Mixture) is Mikuni's classic round-slide carburetor, found on Yamaha XT500, RD350, SR250, and many vintage machines. VM24, VM26, VM28, VM32, and VM34 are common sizes. Known for strong throttle response and simple maintenance.

BS Series (Constant Velocity) CV carburetors with diaphragm-controlled slides. The BS26, BS34, and BS36 are common on Yamaha YBR125, Suzuki GS500, and numerous 1990s-2000s road bikes.

BST / BSR Series Upgraded CV designs with improved fuel atomization. The BST40 is used on Suzuki DR650; BSR37 appears on early Yamaha YZF-R1 models.

TMX / TMR (Flatslide Racing) High-performance flatslide carburetors for off-road competition. Common on Yamaha WR450F and Husqvarna enduro bikes.

Identification

Mikuni carburetors are stamped with a code indicating type and bore size (e.g., "VM28/486" = VM type, 28mm bore). The code appears on the carburetor body or choke plate area.

Aftermarket Rebuild Kits

CarbForge compatible rebuild kits for Mikuni carburetors include all essential wear parts: jets, needle and needle jet, float valve, O-rings, gaskets, and diaphragm where applicable.