Sled Review - Yamaha's 2003 RX-1

Mega Horsepower Four-Stroke!

Jan. 01, 2003 By Gregg Willow
Two-stroke motors have always been the choice for big power, reliability and light weight. The set back has been fuel burn efficiency and exhaust scavenging. This inefficiency has been used against us snowmobilers by the "Greenies", so the manufacturers stepped up to the plate by introducing four-stroke engines. For the performance enthusiasts, these engines lack the power to do anything off the trail and indicating they would never own a four-stroke. Enter Yamaha Motors.

If any manufacturer could create a four-stroke engine that is light weight, reliable and generate some huge power it is Yamaha. Enter the 2003 RX-1.

The awesome 998cc four-stroke powerplant!
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The RX-1 motor is based on their race-bred, high-performance four-stroke engine from their R1 motorcycle generating 145 plus horsepower! Three intake valves for deep breathing and two exhaust valves for exhaling for a total of 20 valves exist in this 998cc power plant. This is one serious performer eating up 800cc twins of the two-stroke variety and creating 65% more low-end torque. It is easy to realize that Yamaha could create a light, high horsepower engine but where does the cold weather reliability come from an electric start four-stroke motor? Start off by a dry-sump oiling system that increases engine power and reduces starting efforts. Then add an electric starter motor that has 1.5 times more cranking power than what exists on typical two-stoke engines. This starting system has been tested at 35? below zero. What is probably most noticeable is the Genesis Extreme exhaust system. Four head pipes shooting straight back in a X-style crossover to a silencer located at the rear then into two exhaust outlets. Not many bends in this system to restrict exhaust flow. Another innovation is that the primary cluth is gear driven to reduce clutch speed and promote belt life. The rubber-isolated gear system is designed to reduce vibration and engine torque pulses for smooth operation.

The engine is not the only innovation in the new RX-1. The new Deltabox chassis has four times the strength of torsional rigidity than it's competitors. Chassis flex is reduced by this new design creating a solid feel on those nasty's. The new design incorporates four high-strength die-castings produced by a high-vacuum, high-pressure process. Lightweight, thin-wall construction and increased strength is the result. The steering column is moved to the right allowing the engine to be mounted lower in the chassis. In fact, the engine center of gravity is 0.8" lower and 2.0" further back than the SRX. And if you are concerned about weight, the RX-1 comes in about the same as the SRX with electric start.

Yamaha's new wishbone front suspension.
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Trailing arms are a thing of the past as their new double wishbone front suspension moves through 9" of vertical travel with zero bump-steer and no spindle caster angle change for razor-sharp handling in the bumps. Double wishbone front suspension design maintains accurate ski-to-ski alignment providing consistent ski tracking in bumps or when riding at high speed. Yamaha states that the "front suspension geometry maintains the spindle angle at a stable 23? so that steering effort remains consistent throughout the full ski travel. Unequal length A-arm design minimizes ski center-to-center change (ski scrub) for consistent handling on rough, rutted trails. New large 40mm diameter high-pressure shock absorbers increase shock fade resistance. Progressive ratio stabilizer system sharpens cornering and big bump response. New lightweight plastic skis, with dual-angle keel, give accurate steering with low steering effort".

The rear suspension is the Pro-Action SXV found on the Viper. The center shock has been increased to 40mm to reduce shock fade.

The RX-1 ER with reverse.
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There has to be a lot said about the styling and comfort of the RX-1. It looks like a more aggressive SX Viper, if that could happen. The RX-1 can also come with reverse in the red RX-1 ER version. For the mountain riders, there is the RX-1 Mountain with 151" Camoplast Predator track and 2" luigs. The dash sports the LCD gauge used on the Viper and is now back-lit for easier night time reading. Digitally-controlled hand and thumb warmers are an industry first and the LCD gauge displays the settings. The 425W magneto system powers the new dual headlights and are the brightest in the industry. The throttle is a new "easy-pull" lever that has a shorter pull distance and the hydraulic brake is the dual-piston variety for efficient cooling.

RX-1 Specifications
Type / Displacement / cc 4-Stroke, 998cc
Cylinders Four
Cooling Liquid
Bore & Stroke / mm 74.0 X 58.0
Intake Design 3 Valves
Carburetion Mikuni BSR37 X 4
Ignition Digital D.C. C.D.I. w/T.P.S.
Exhaust 2 Valves, Rear Exhaust
Clutch / Transmission YVXC, Variable Ratio
Disc. Brake Type Hydraulic, Ventilated Disc, Adj. Lever
Front Suspension Independent, Double Wish Bone
Front Shocks Alum. H.P. Gas, 40mm Dia.
Front Travel / in. 9
Ski Type Plastic, Dual Angle Keel
Carbide Ski Runners Standard
Stabilizer Bar Standard, Progressive Ratio
Rear Suspension Proaction SXV with Quick-Adjust and Adjustable Control Rod
Rear Shocks Alum. H.P. Gas, 40mm Diameter
Rear Travel / in. 11.5"
Overall Length / in. 108.4
Overall Width / in. 47.5
Overall Height / in. 46.6
Track/Width x Length x Height / in. 15 X 121 X 1.00
Ski Stance (ctr. to ctr.) in. 42.1
Fuel Capacity / Gal. 10
Oil Capacity / Qts. 3, Dry Sump.
Electric Start Standard
Reverse Optional
Hand & Thumb Warmers Standard, H/Bar Adjustable, Separate
Windshield Height Mid
Mirrors Optional
Seating Capacity One
Tow Hitch (Optional)
Tunnel Protectors Standard
Headlight Watts, Type 60/55W Halogen x 2
High Beam Indicator Standard
Oil & Temp Light Standard
Fuel Gauge Type Electric (LCD), Low Fuel Warning Light
Speedometer Standard (LCD Digital)
Odometer Standard (LCD)
Tripmeter Standard (LCD)
Tachometer Standard, Backlit (Stepping Motor Drive)
Color Team Yamaha Blue/White; Twilight Black; Liquid Silver (Spring Only)
Warranty 1 year
Carbon Fiber Print Exhaust Covers
Carbon Fiber Print Headlight Mask
Carbon Fiber Print A-Arm Covers
Chrome Sport Windshield
Custom Touring Kit
RX-1 Rear Rack
Deluxe Rear Trunk Bag
Combination Sport Luggage
Rear Rack Backrest Pad
Running Board Sno-Grips
"Open" or "Closed" Rear Axle Guide Wheels
Ultra Skid Plate
Camoplast Predator Tracks
RX-1 Footboard Traction Bracket
Colored Hyfax
RX-1 Deluxe Cover
RX-1 Custom Cover

I can talk all day about the new RX-1 but as the old saying goes "a picture is worth a thousand words". If that's true, then a video clip has to be worth a million. If you do not have DSL that's okay, it is worth the wait. Oh yeah, be sure to turn up the sound on your PC!


All Dial-up Modems Download MPEG File Approx 2.6 MB Frame Width: 192 pixels

DSL, Cable & Quicker Media Player 6.4 Streaming File Frame Width: 240 pixels

The new RX-1 is definitely the new standard of future snowmobiles. You can now have the best of both worlds. Four-stroke efficiency with two-stroke power. Imagine no more pulling of the starter cord, no more adding two-stoke oil, and better gas mileage. Only a year ago anyone outside of the Yamaha development team would have said it could not happen. Who would of thought?

Can the other manufacturers step up to the plate? It looks like they have no choice. As I rub my crystal ball to predict the future... Ahh forget about the crystal ball, it sure did not pick up on Yamaha's new four-stroke. The Yamaha dealers are going to sell a lot of RX-1's this next season, period!

For more information on the RX-1 and the RX-1 ER, check out Yamaha's Website at

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