Honda CB750 Carburetor Identification: SOHC vs. DOHC, Keihin vs. VB

The Honda CB750 ran from 1969 to 2003 across two completely different engine families — SOHC and DOHC — and the carburetors are not interchangeable. Here's how to identify what you have.

SOHC CB750 (1969–1978): The Original

The original CB750 K and F models use a bank of four 28mm Keihin carburetors. Early K-series bikes (1969–1975) use the Keihin PW series. The 1976–1978 F-series use slightly updated versions. All four carbs are identical and interchangeable within the same year range.

Key identifiers on SOHC carbs:

• Cast number on the body (e.g., "XW" for early K models)
• Main jet size stamped on the main jet (stock is typically #105–#108 depending on year)
• Single round slide vacuum port on later F models

DOHC CB750 (1979–1982): Completely Different

The CB750 F and C DOHC models switched to a four-carb bank with 32mm Keihin VB carburetors. These look similar but are larger and tuned differently. They are not interchangeable with SOHC carbs.

Common CB750 Carb Problems

• Stuck float needles — causes flooding or no-start after sitting
• Cracked pilot screws — the brass pilot screws are often snapped by overtightening
• Clogged pilot jets — the #35 pilot jet clogs easily with old fuel varnish
• Worn slide needles — causes rich running at mid-throttle

Buying Used CB750 Carbs

Always buy as a matched set. Mixing years or rebuilding partial sets causes sync problems that are nearly impossible to tune out. Check for cracks in the carb bodies at the inlet boots — these are often missed and will cause air leaks.

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