Big bore kit 300cc wiseco VHM, NSR250 MC18/MC21/MC28

Big Bore Kit, NSR300, Wiseco, VHM *

This 300cc Big Bore Kit is identical to the TPER-0007 300cc Big Bore Kit, but the standard 300cc heads and pistons are replaced with high performance options.

In this case we have forged Wiseco pistons that are lighter and stronger than stock, and also changable insert VHM cylinder heads, which have been specifically developed by TYGA and VHM for use with the TYGA 300cc Big Bore Kit.

See below for performance details for TPER-0007.

Bore & Stroke is 59mm x 54.5mm giving a total displacement of 298cc.

Parts included in the NSR300 kit.

Cylinder x 2 (includes head studs, RC valve, pulley, nut and washers)

Rear Head x 1

Front Head x 1

Piston x 2

Ring set x 2

Piston Pin x 2

Piston Clip x 4

S/E Bearing x 2

Head gasket x 2

Cylinder gasket x 2

RC Valve cables x 4

Water hose x 1

Exhaust Manifold x 2 (to fit TYGA pipes)

Other information:

There is no problem about the RC valves hitting the piston due to thin cylinder wall thickness. This is not an issue on our kit as it’s using different

cylinders, not modified NSR250. They are genuine OEM Honda cylinders, made and plated in Japan to their typical high quality.

The RC valves are easier to adjust than ever on the 300 kit, as there’s only one adjuster screw to play with, and each cylinder marked at the correct ‘fully open’ position for simple setting.

Exact Jetting requirements for your area and application cannot be provided due to differing atmospheric conditions around the world. However, following are some base settings to work from:

MC21 Std bottom end, Wire splice, TYGA Pipes, Airbox lid mod with filter.

Temp: 29 C

Press: 1015mb

Hum: 65%

Alt: 30m

MJ – #182/#185

JN – Std./Std.

SJ – #38/#38

AS – 1.5 turns out

PwrJ – Std./Std.

Tip: Cooler temps, higher pressure and/or lower humidity require richer jetting. High altitude requires leaner settings. Starting off with rich settings will in the worse case foul a plug. Too lean a setting may destroy the engine.

This jet set-up is for guidance only. TYGA Performance cannot be held responsible for any engine damage incurred due to incorrect settings.