PROX piston kit for YAMAHA WR 426 F, YZ 426 F from 2000 to 2002

PROX offers this piston kit for YAMAHA WR 426 F, YZ 426 F from 2000 to 2002. The piston slides in the cylinder and takes the force of the air-fuel combustion, passing it to the connecting rod and crankshaft.

Forged or cast piston?

• Forged: hot-pressed then machined aluminium, stronger when hot and lighter for the same strength; sometimes fitted with a little more clearance, and costs more.
• Cast: aluminium poured into a mould, like most OEM pistons; it expands little, runs quietly and costs less, but tolerates overheating less well.
• In short: forged for racing or a tuned engine, cast for a stock engine used for leisure riding.

Why choose PROX?

ProX has its pistons made in Japan and the USA, with Japanese rings (Riken, TP or NPR) and tolerances at least equal to OEM; most of its four-stroke pistons are forged.

When should you replace the piston on your YAMAHA YZ 426 F?

Harder starting, loss of power, blue smoke, oil consumption or a knock when cold: these are the signs of a tired top end.

No manufacturer hour figure for this model. Cross-Mania guideline: compression check every 30 h in hard use and every 60 h for leisure.

Specifications and fitting tips

• Displacement: 426 cm³
• Piston material: Aluminium alloy
• Skirt coating: Uncoated
• Compression ratio: 12.5:1
• Engine: 4-stroke
• Kit includes piston, rings, wrist pin and circlips

Available in several sizes: choose the one that matches your cylinder (stamped size or measured bore). Diameters: A = 95.00 mm, B = 94.96 mm.

Cross-Mania tip: Measure the cylinder bore before ordering: the piston must match your cylinder size. Follow the manufacturer's break-in procedure and replace the top-end gaskets at the same time.

Also needed with this part

• Top-end gasket kit : ATHENA · PROX
• Spark plug : NGK · NGK CR8E
• 4-stroke engine oil : LIQUI MOLY 10W40 1 L · MOTUL 10W50
• Air filter : TWIN AIR over-filter for FANTIC XE, XX… · HIFLO FILTRO

Compatibility

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

Fits:
YAMAHA WR 426 F 2002
YAMAHA WR 426 F 2001
YAMAHA YZ 426 F 2002
YAMAHA YZ 426 F 2001
YAMAHA YZ 426 F 2000