Last season we told you about a new set of RAD Valves from Boyesen that had been developed specifically for the big-block Polaris twins.
Previously, Boyesen offered what was called a #63 version of their popular dual-stage RAD Valve design, but this version left some performance on the table. Boyesen, along with the help of Hot Seat Performance, set out to improve upon the #63 RAD design and came up with the #65 that was first available in limited quantities early last year (2003), and was offered full-force for the 2003-2004 winter season.
Well, the jury is in, and the #65 RAD Valve has been very successful. So much so, that Boyesen has had a difficult time keeping up with the demand. â€œWe can hardly make them fast enough!â€
For years, Boyesen RAD Valves have been the reed of choice in the motocross world and are quickly gaining acceptance in the snowmobile market. Like other Boyesen reed designs, they utilize the Dual-Stage Pro Series Reeds (also available to fit your stock reed cages for most every snowmobile with reed intake). This design combines a super-sensitive (lighter) carbon fiber reed as the top layer, with a durable fiberglass bottom reed. The lighter, top reed responds quicker and provides a crisper throttle response at partial throttle positions and lower engine RPMs. The stiffer, bottom reed is â€œportedâ€ to provide maximum airflow and horsepower at higher RPMs.
The benefits of this dual-stage reed design is a package that better responds to both low speed and high speed airflow, resulting in more power and improved responsiveness across the entire powerband.
Then we get to the RAD Valve cage design. Each Boyesen RAD Valve is a solid, seamless one-piece casting. No distortion, no loose inserts or parts to rattle into the engine. Each valve fits perfectly with your stock manifold. None of this plastic like the OEMs use, which trade off some performance for cost savings.
According to Boyesen, their RAD Valve provides aerodynamic directional dividers that channel the incoming fuel-air charge for increased intake velocity. It not only sounds good, but it works.
What we notice is the dimensionally precise construction of the aluminum cages and the perfect fit. Never do you need to cut and destroy part of the stock intake boot to get them installed. Gaskets are included with each RAD Valve, and installation is as easy as removing your airbox and carbs. Reed durability has been excellent in our experience, and if the price of the entire cages is too steep then consider just installing the Power Reeds in place of your stock ones as a â€œStage 1â€ improvement (this is true for any sled that needs a new set of reeds).
Weâ€™ve used various RAD Valves over the years, but never have we experienced such a profound improvement as the #65 RAD Valves. They technically replace the previous #63 RAD Valve for all Polaris twins, and the bigger the engine is the more noticeable the difference. While they work just fine on a stock engine package, anytime you begin to increase the airflow on a Polaris big block the RAD Valves make more and more of a difference. As you make more airflow mods to your motor (intake and exhaust), the stock reeds become more of a restricting factor the further you go.
Required jetting changes are minimal. If your sled is currently jetted properly, start where youâ€™re at when you install the RAD Valves. They pull more air and fuel, so changes (if any) will be minimal. If you have stock jetting installed, drop the mains one size and start there. Weâ€™ve found this to be very accurate. You wonâ€™t have to do a bunch of tuning if the RAD Valves are the only thing youâ€™re changing from a known working set-up.
Right now, our set of #65 RAD Valves are installed into our 2003 Polaris RMK 800 that has been tweaked even further with several intake modifications from Starting Line Products (Air Horn Kit and Flow Rites) and a SLP Single Pipe Exhaust system, forming a potent combination thatâ€™ll bring a smile to most every RMK ownersâ€™ face. This baby rocks!
Boyesen even goes as far as to provide a written guarantee; â€œYou will experience increased power and throttle response. If you are not completely satisfied with any Boyesen product, return it for a full refund.â€
The #65 RAD Valves for Polaris twins will cost you $268.75 (retail) for the set of two complete cages. If you want just the Power Reeds thatâ€™ll fit your stock Polaris twinâ€™s reed cages (part #568) thatâ€™ll run only $80.09. RAD Valves and Power Reeds are available for most every reed intake snowmobile (and motorcycle) ever built. Call them at 800-441-1177 or order from one of many dealers/distributors, including High Performance Engineering (800-451-5268) or Hot Seat Performance (651-982-0600).