Banshee 421cc Stroker Engine Rebuild Kit ARES 68mm Cylinder +4mm Crank Cool Head

Banshee 421cc ARES 68mm Athena-Style Stroker Big Bore Complete Engine Kit

Athena-Level Performance. Proven BPRATV Value.

The BPRATV Banshee ARES 68mm Cylinder Kit is engineered for riders who want serious horsepower, long-term reliability, and unbeatable value. Featuring a factory pre-ported dune/play port design, larger water jackets, and triple exhaust ports, this kit is ready for +4mm stroker builds with no spacer required.

🔥 Built to Perform – Complete 421cc Stroker Rebuild Kit

This complete top-to-bottom rebuild kit replaces higher-priced Athena cylinders with BPRATV ARES Nikasil cylinders that deliver true performance porting—not marketing gimmicks. Designed to compete directly with Cub-style builds, this kit can achieve 95+ HP on pump gas with proper tuning.

• BPRATV ARES 68mm Nikasil cylinders – factory dune/play ported (ACTUALLY PORTED, no gimmicks)
• Triple exhaust ports with larger port windows for a wide, responsive powerband
• Larger water jackets for superior cooling under high-load conditions
• Wiseco Pro Lite forged STROKER pistons with rings, pins, and circlips
• Hot Rods Heavy-duty wrist pin bearings
• Special-cut 68mm big bore + 4mm stroker 22cc domes
• Pro Design Cool Head with head stud kit and O-ring kit
• Cometic one-piece custom fiber base gasket and intake gaskets
• Hot Rods complete +4mm stroker crankshaft with 115mm heavy-duty rods (true & welded, ready to install)
• Complete Yamaha Banshee engine gasket kit
• Complete Yamaha Banshee engine seal kit

📦 Extra Components Included at No Additional Cost

This kit includes critical extras that many sellers charge separately, ensuring your build goes together correctly the first time.

• BPRATV Talon Titanium Acorn Cap Nuts (Pro Design heads do not include nuts)
• Set of four new cylinder dowel pins – essential for any fresh build
• New pair of NGK spark plugs for reliable first start-up
• 1-year manufacturer warranty for peace of mind*

🚨 Port Timing Matters – Even on Pre-Ported Cylinders

This 421cc kit is drop-in and bolt-on ready, and the cylinders are already factory dune/play ported. However, porting and port timing are not the same thing—and this is where many builds leave power on the table.

Porting refers to the shape and flow characteristics of the ports (which is already done). Port timing refers to when those ports open and close in relation to the crankshaft. When stepping up to a 421cc +4mm stroke, the piston travels farther, which changes the effective timing—even on a pre-ported cylinder.

• Cylinders are dune/play ported, but timing is optimized for 392cc–400cc setups
• Correcting port timing restores ideal piston-to-port relationship for a +4mm stroke
• Thick base gaskets only raise the cylinder and hurt compression and power
• Proper timing unlocks stronger mid-range, cleaner revs, and higher peak power
• Use BPRATV’s in-house port timing service to get everything this kit can deliver

✅ Compatibility & Nikasil Advantages

Designed for Yamaha Banshee YFZ350 models from 1987–2006. The Nikasil-plated aluminum cylinders provide superior durability, cooling, and piston life compared to traditional sleeves.

• Transfers heat more efficiently to keep engine temperatures lower
• Harder, smoother piston surface reduces friction and wear
• Longer service life between rebuilds
• Lightweight aluminum design improves throttle response
• Proven across 392cc, 400cc, and 421cc Banshee builds

Athena vs CPI Cub vs BPRATV ARES

Athena and CPI Cub cylinders have long been respected benchmarks in high-performance Yamaha Banshee builds. Athena is known for proven durability and consistency at a premium price point, while CPI Cub cylinders are recognized for race-focused power and Nikasil longevity. The BPRATV ARES cylinder bridges the gap—delivering Athena-level performance, strong power potential, and proven reliability with exceptional overall value for serious riders.

❓ Frequently Asked Questions (FAQ)

🌟 Why Buy from BPRATV? Trusted Banshee Performance Experts 🌟

At BPRATV, our promise is unwavering: The Best Parts. The Best Performance. The Best Price. Every ARES kit is tested across real-world Banshee builds to deliver reliable, repeatable power. Trust BPRATV to keep your Yamaha Banshee running at its best, every single time.

🔥 Upgrade your Yamaha Banshee with the ARES 68mm Cylinder Kit – power, precision, and reliability in one package! 🔥

© BPRATV LLC 1-year limited warranty from the manufacturer for material or workmanship defects.*

Due to the nature of high performance and racing applications, BPRATV LLC components are sold without express or implied warranty. This product is exempt from emission standards under 40 C.F.R. § 1051.620 and is sold for closed-course competition use only.