PROX Piston Kit for YAMAHA XT 600 1984-2004

On YAMAHA XT 600 from 1984 to 2004, the PROX W4607M10100 piston kit (Ø 101 mm) fits in place of the original part. At the heart of the top end, the piston soaks up the heat and pressure of every explosion. As it wears, the rings no longer seal against the cylinder: compression drops, power drops with it, and the risk of seizure goes up.

Key features

• Made mainly in Japan, by OEM manufacturers (ProX catalogue).
• Complete kit: piston, rings, pin and circlips.
• Compatible with stock coated (Nikasil) and sleeved cylinders. Not suitable for chrome-plated cylinders.
• Diameter classes to the hundredth of a millimetre for a precise piston-to-cylinder clearance.

Specifications

• Brand: PROX
• Manufacturer part number: W4607M10100
• Piston diameter: 101 mm
• Engine: 4-stroke

When to replace it?

• Loss of power, sluggish pick-up, harder starting: compression is dropping.
• Piston slap on a cold engine, getting more and more noticeable.
• On teardown: vertical scoring on the skirt, stuck or worn rings, thick carbon on the crown.
• On a four-stroke: oil consumption, blue smoke and a fouled spark plug.

Replace the piston as set out in your bike's service manual, sooner if you race, and straight away as soon as these symptoms appear. As a Cross-Mania guideline, plan for a new piston every 50 to 100 hours of engine running depending on whether you race or ride for fun. Always measure the cylinder at the same time: a new piston in an oval cylinder won't last.

Fitting tips

1. Clean the cylinder and check it: diameter, ovality, taper and condition of the bore coating.
2. Check the end gap of each ring in the cylinder against the figures in the manual or the manufacturer's instructions.
3. Fit the rings with the mark facing up and the gaps staggered, never letting the ends of the oil control ring overlap.
4. Fit the piston with its arrow pointing to the exhaust side, oil the pin and the small end, then fit the circlips without distorting them, gap opposite the notch. A circlip that has been taken out is replaced with new piston pin circlips, never refitted.
5. Reassemble with a new top end gasket kit and tighten the cylinder head in a criss-cross pattern to the manufacturer's torque.
6. Fit a new spark plug and change the oil, with fresh engine oil and a new filter.
7. Break the engine in: warm it up gently, vary the revs and avoid sustained full throttle for the first hour.

Why PROX?

ProX Racing Parts has been supplying engine and clutch parts to motocross riders since 1975, from its headquarters near Amsterdam. According to its catalogue, most of its parts are made in Japan, by manufacturers that also produce parts for the Japanese motorcycle makers.

Spare parts and items to plan

• Piston rings : WOSSNER · PROX
• Piston pin : WOSSNER WP009-SP · WOSSNER CW22
• Top-end gasket kit : CENTAURO 990A607TP · CENTAURO 990A602TP
• Spark plug : NGK 650 L
• 4-stroke engine oil : LIQUI MOLY 10W40 1 L · MOTUL 10W50

Frequently asked questions

Does the kit include the gaskets?
No: the kit contains the piston, rings, pin and circlips. Add a top end gasket kit, because a head or base gasket can never be reused.

Can I replace just the rings later?
Yes, as long as the piston and cylinder are still within tolerance. Replacement rings can be ordered on their own, as can the piston pin and the circlips.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
YAMAHA XT 600 2004
YAMAHA XT 600 2003
YAMAHA XT 600 2002
YAMAHA XT 600 2001
YAMAHA XT 600 2000
YAMAHA XT 600 1999
YAMAHA XT 600 1998
YAMAHA XT 600 1997
YAMAHA XT 600 1996
YAMAHA XT 600 1995
YAMAHA XT 600 1994
YAMAHA XT 600 1993
YAMAHA XT 600 1992
YAMAHA XT 600 1991
YAMAHA XT 600 1990
YAMAHA XT 600 1989
YAMAHA XT 600 1988
YAMAHA XT 600 1987
YAMAHA XT 600 1986
YAMAHA XT 600 1985
YAMAHA XT 600 1984