Athena Big Bore Cylinder 478cc Yamaha YZF 450 R 09-25

Athena Big Bore Cylinder 478cc for Yamaha YFZ 450 R and YFZ 450 X.

This is not a replacement part, it is a serious upgrade. By increasing the bore to 98 mm and the displacement to 478.2 cc, the engine’s character changes completely: more torque from low revs, a much fuller power delivery, and a constant push as the engine starts to rev out.

The 12.5:1 compression ratio makes each combustion more effective, so you’ll notice the engine responds more directly to the throttle and gains strength across the entire range, especially in areas where the stock cylinder falls short.

The Athena cylinder is made of aluminum with an internal nickel and silicon coating, allowing it to operate at higher temperatures and loads without compromising wear. The forged piston is designed to withstand this increased demand, maintaining stability even under intensive use.

On the test bench, it’s clear: the engine gains power throughout the entire rev range and keeps pushing where the original drops off, reaching up to 46 hp with the right electronics.

The kit includes cylinder, piston, rings, wrist pin, and gasket set.

Technical specifications

• Brand: Athena
• Reference: P400485100047
• Displacement: 478.2 cc
• Bore: 98 mm
• Stroke: 63.4 mm
• Compression ratio: 12.5:1
• Weight: 2.17 kg

Compatible models

YAMAHA

• YFZ 450 R 2009-2013
• YFZ 450 X 2010-2011

Attention! The included gaskets are specifically developed for Athena cylinder kits. Every time the kit is disassembled, replace the gaskets with the specific Athena set. Do not use OEM gaskets.