VFR750R-RC30 Carburettor Tuning

The standard RC30 VD carbs perform rather well, and good performance can be found with little modification.

HRC produced a TT-F1 jet kit, comprising of replacement vacuum pistons (commonly referred to as "slides"), emulsion tubes, jet needles, jet needle shims, and pilot [slow] jets.

Essential for street when aiming for maximum performance, and [highly recommended] for race use, a foam "dome" filter should be used. These are available from ITG, at approximately £175 [2017]. The HRC kit manual suggests running the carbs open, and in 1991 supplemented the kit instructions to include grinding away the separating ribs on the carb tray, drilling the sides of the tray, and opening up the venturi for increased flow. [See below]

NL0 kit bikes were often fitted with Keihin FCR39, and factory supported NL0B bikes with TR38s. Full factory RVFs were later fitted with magnesium TR carbs, up to 43mm.

Gains from the FCR39s are negligable on NL0 spec motors, but certainly perform well at very high rpm.

VFR750R MR7 Carbs

RC30 [Std.] VD Carbs

Use MR7 tray & [recommended] airbox gauze.
ITG or similar foam filter highly recommended.

Keihin FCR39

Moriwaki RC30 FCR kit

Good for top-end & over-rev.
Generally loses bottom-end & mid-range.




HRC Factory NL0W

RVF Magnesium Carbs

Factory carbs were produced up to 43mm

1991 HRC Inlet Mod

Modify RC30 VD carburettor

  • Shave off the shaded portion (rib, throwaway boss) until the surface is level with the bottom surface.
  • Use a drill and make 08 to 09 holes on the side wall (see photo). Make as many holes as possible. If the holes are too close to each other, however, the rigidity will deteriorate. Therefore, make sure to maintain the minimum thickness of 2.5 mm.

1991 HRC Inlet Mod

Modify RC30 VD carburettor

  • Shave and widen each bore mouth according to the diagram.
  • Make sure not to shave off the tightening boss at the bore mouth.