Engine
The VFR750F series all used 748 cc 16-valve gear driven DOHC liquid-cooled 90° V4 engines with carburetor-based air/fuel induction; the bore/stroke remained the same for all 750 models at 70.0 x 48.6 mm (2.756 x 1.913 inches). The engine was made of cast aluminium alloy with the crankcase being divided horizontally, VFR750P and VFR750K models use slightly different crankcases with the lower casing being modified to allow for the gear position indicator in place of the neutral switch. On all the VFR750 models the gear drive for the cams was between the cylinders. Lubrication was via a wet sump with a chain-driven, dual-rotor oil pump; an oil (air) cooler was also fitted. Transmission was a 6-speed, with a constant-mesh, wet multi-plate clutch and chain drive to the rear wheel with the exception of the 5-speed VFR750P which featured a spacer in place of one of the gears.
The VFR750F uses a 180 degree crank, instead of the 360 degree crank used in the VF and VFR750R.
In comparison to the VF750 almost every component had weight shaved off it, each con-rod lost 90g, rocker arms 6g, intake valve 0.5g, exhaust valves 1.5g, pistons 20g, piston rings 1.3g per set, valve springs 17g each.
The V4 engine has proven itself highly reliable, with few known faults. The gear-driven camshaft system removed any lingering concerns about cam-chain maintenance, which had dogged the VF-series of Honda V4 engines. Valve adjustment on first-generation VFR750Fs was by screw and locknut, which changed in 1990 to shim-under-bucket, along with the valve-clearance inspection interval (to 16,000 miles). However, RC36 engines have been known to reach well over 50,000 miles without any need to adjust the valve clearances.
Second- and third-generation VFR750Fs have notoriously suffered from failed regulators/rectifiers, likely caused by heat damage. Although Honda eventually re-designed the replacement part, such that failures of the new, finned regulator/rectifier are rare, some VFR750F owners carry spare regulator/rectifiers or even install small cooling fans to prevent reg/rec units from overheating.
Read more about this topic: Honda VFR750F
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