Banshee Athena 392 to 421 Cylinders Conversion Top End Kit Wiseco Pistons +Domes

421cc Athena Big Bore Banshee Top End Kit

No Spacer Needed – 4mil Stroker Ready

Unlock serious power from your Yamaha Banshee with this all-in-one top end conversion kit designed for use with a +4mm stroker crankshaft – no spacer required! Transform your 68mm Athena 392cc setup into a roaring 421cc beast that delivers instant results and long-term reliability.

🔥 Built to Perform – No Shortcuts

This kit is engineered to eliminate guesswork. You’ll receive:

- Athena 68mm Nikasil-Plated Cylinders (Set)

- 68mm Wiseco Pro Lite Forged Piston Set w/ Rings, Pins, Circlips

- Heavy Duty Wrist Pin Bearings

- Special Cut 68mm Big Bore 4mil Stroker 22cc Domes

- BPRATV Talon Titanium Cylinder Head Stud Kit

- Cometic Fiber Base Gasket

- Intake Gaskets & Cool Head O-Ring Kit*

- 4x New Cylinder Dowel Pins

- 2x NGK Spark Plugs – Just Fire It Up!

*Fits all Pro Design-style heads. Mod Quad heads require a different kit—contact us after purchase if needed.

🚨 Port Timing Is Critical – Don’t Skip It

This 421cc setup must be ported properly. The Athena port timing is made for a 392cc configuration from the factory. Slapping in a thick base gasket is NOT a real fix and WILL rob your Banshee of its true potential and a waste of your money!

We strongly recommend:

- Correcting port timing to match 421cc stroke

- Watching Herr Jugs Racing's "Banshee Porting 101" for clarity

- Using our in-house BPRATV porting service for max performance

❓ FAQ

- Will this kit work with my OEM crank?
No. A +4mm stroker crank is required. Hot Rods #4111 is recommended.

- Do I need to port the cylinders?
Yes. This is absolutely necessary to get full performance from your 421cc setup.

- Is porting included?
No, but we offer it in-house—contact us after purchase for pricing.

- Does this fit all Banshee years?
Yes. This kit fits all Yamaha Banshee years and models when used with a 4mil crank.

- Are the parts new?
100% brand new, sealed in original packaging.

Don’t let a weak top end hold you back. Upgrade your Banshee the RIGHT way!