Banshee Athena 392 to 421 Cylinders Conversion Top End Kit Wiseco Pistons +Domes
Banshee Athena 392 to 421 Cylinders Conversion Top End Kit Wiseco Pistons +Domes
S410485301023, S410485301024, P400485850351/1, 13077M06800, 9768M06800, BR8ES, PD300A, 2GU-11321-00-00, 2GU-11311-00-00, 2GU-11181-00-00, 2GU-11111-00-0, 3GG-11351-02-00, 2GU-11631-00-94, 2GU-11610-01-00, 93450-17129-00, 93310-316D6-00, 4L0-11633-00-00, BR8-ES000-00-00, B8E-S0000-00-00, 91830-21014-00 99530-10014-00 99510-10114-00, PD909
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!
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NOTICE REGARDING PHOTOS: Product photos used in our listings are for example only to show the high quality of our components. You will receive the correct quantity, size, and fitment of bearings, titanium fasteners, nuts, and bolts for the specific kit listed.
BEARING NOTICE: In some cases, you may receive SEALED bearings. If your application requires an OPEN bearing, the seals can easily be removed.
EMISSIONS & RACE USE ONLY: This product is exempt from emission standards and requirements of 40 C.F.R. § 1051 as provided by 40 C.F.R. § 1051.620, and California law [e.g., vehicle code §§ 27156 and 38391]. Sold ONLY for use with EPA-certified, purpose-built, nonroad vehicles used solely for closed course, nonroad competition/racing. Installation may void vehicle manufacturers' warranty and/or may be illegal in some locations.
WARRANTY & LIABILITY: © BPRATV LLC 1-year limited warranty from manufacturer for material/workmanship defects.* Due to the nature of high performance and racing, components are sold without express/implied warranty of merchantability or fitness for a specific purpose. BPRATV LLC shall not be liable for specific, incidental, or consequential damages (loss of property, equipment, profits, or revenue) resulting from sale, installation, or use of these parts. This product is NOT DIY; we strongly recommend work be done by a qualified, experienced mechanic.
RETURNS: Returns accepted within 30 days for items 100% complete, brand new, and in original packaging. Items installed or prepped (lubricated/sealed) are ineligible. For warranty consideration, parts MUST be sent back for physical inspection. No exceptions. We do not warranty based on photos, emails, or third-party assessments.
SPECIALTY WARRANTIES: Cub Cylinders: Lifetime warranty for original owner via BPRATV/Millennium Technologies inspection; covers cylinder only. Titanium Fasteners: Failure during use results in replacement only. Neither warranty covers improper tuning, installation, maintenance, or misuse.
INTERCHANGEABLE PARTS: We may substitute parts of equal quality from different manufacturers to prevent backorder delays. Prices and listings subject to change without notice.
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