2003 yamaha rx1

To make sure this large investment would be successful it would not have been acceptable to just put the engine in a present chassis. The complete snowmobile would have to be redesigned to assure a quantum leap forward and present the customer with a sled so advanced there would be no question that this was a large step into the future.

The result far outstripped what we had come up with in our lunch hour brainstorm.

"American Snowmobiler was closer than any other magazine in their speculations" said Gordy Muetz when he was showing the new RX-1 machine at the 2002 Eagle River World Championship. "You predicted 120 hp from 1200cc, we actually have 150 hp from 1000cc. You were way too conservative on power." Hey, we were just brainstorming for an interesting article, we had little hope that we would actually experience a machine like that in the near future.

Yamaha surprised us, as well as the whole snowmobile industry, when they rolled out the RX-1. The RX-1 is not just a four stroke hot-rod shoe-horned into an existing chassis. The chassis is completely unique, and twice as stiff in torsion as the SRX, greatly improving control of the suspension components.The engine location follows the new" mass-centering" concept presently popular in high performance sleds. The engine is tilted back 30 degrees towards the tunnel, with the carbs mounted in front, and the exhaust exiting straight back under the seat. This accomplishes a number of neat things. First, the exhaust system is totally removed from the front of the sled, allowing a much narrower frame and a very sleek styling of the hood. The rearward location of the motor also allows for a centrally mounted A-arm front suspension.

The resulting long arms reduce bumpsteer, camber changes, and scrub to a minimum through its long travel. The whole front frame is of a "perimeter style design" cradling the engine, suspension mounts and clutch parts in a rigid construction involving several castings. Despite its complexity, the rigid chassis is said to weigh less than the SRX chassis. Yamaha achieved this by an exclusive casting technology, which is used today in places like the suspension of a Porsche 911, and the chassis of Ferrari and Audi cars. Jointly developed by Yamaha Motor and Hitachi Metals, this method is known as HV die-casting and maintains high strength through very fine granulation in the aluminum structure, especially in thinner parts.

High performance four stroke engines have unique problems not experienced with two strokes. One such feature is pronounced engine braking. With a standard belt set up, the belt would actually start slipping on the sheaves under deceleration, and the braking effect would then disappear. A similar situation actually occurred with the new four stroke GP motorcycles, where the engine braking would be more than the tires could take, resulting in unruly rear wheel behavior entering corners. The motorcycle racers had to use clutches that slipped under deceleration to solve the problem.

A belt that constantly slipped would quickly wear out, so Yamaha solved the problem by loading the weights harder in the lower ratios. The clutch calibration is totally different, both in the primary and secondary clutches. The flyweights are rumored to weigh around 80 grams, the largest ever seen on a stock snowmobile.
This heavy weight is also needed for acceleration, as the four stroke engine develops more torque than a two stroke in the mid-range. Another factor contributing to the need for heavier weights, is the 20% reduction gearing from the engine to the primary clutch. When the engine is spinning at 10,500 rpm, the clutch is only turning at 8500 rpm. This increases the already healthy torque by 20% at the primary clutch. Yamaha engineers speculated that even better performance could be experienced with heavier weights, but the present clutch does not allow larger weights for space reasons. Yamaha officials admit clutch parts may be the first hop up products for this model. We predict a run on after-market 4 flyweight clutches.

Not that there is any lack of acceleration in a typical trail situation. Test riders are reporting amazingly strong mid-range acceleration, and let's face it, that is how we ride most of the time. The RX-1 easily out accelerates the SRX, Yamaha's previous top dog. The SRX was a match for even 800 or 1000cc sleds, witness the success SRX riders, such as Pat Hauck, have had winning even the stock 800 triple class with a 700 SRX.

A lot of Yamaha testing takes place at a secret site in Sweden. Our spies in the area tell of a test last year where one of Sweden's top sno-cross racers lined up his 800cc open class machine against the RX-1 on the lake for a quarter mile drag race. With 165 hp and a stripped down chassis, the money would have been on the race machine, but by the midway point, the RX-1 pulled away and at the quarter mile mark it held a 5 sled length lead over the race sled. We hear similar stories from other test-drivers.

One of the keys to the strong mid-range torque is Yamaha's choice to use a 4 into 2 exhaust layout. A simple 4 into 1 exhaust would have left the engine weak in the low to mid-range area, with an inevitable torque valley. The 4 into 2 exhaust enters into a chambered muffler which exits into two motorcycle style outlets with a very distinctive sound.

The reaction to Yamaha's new RX-1 sled has been one of genuine excitement. Watching the acceleration of the sled around the Eagle River oval in the hands of Bobby Donahue amazed even the most skeptical spectator. The group around the machine was 10 deep for the rest of the weekend. Yamaha is placing several machines in the hands of grass drag racers this fall and the racing organizations have classified it to run in the 700cc triple pipe class on the grass. Will the heavier machine do well against lighter machines in 500 feet? We think it will be a question of clutching it right, and that may take half the season. Quarter mile speed runs should be a different story, top end speed is this machine's strong card.

It is also interesting to note a number of different reactions to this new machine.

Veteran Tom Anderson, best known for his snowmobile shows, is looking forward to turning his RX-1 into a "cruiser." He likes the idea of having plenty of power on tap if needed, but feels the suspension and smooth power delivery will make it an ideal all around trail machine.

The "never enough" crowds are lining up turbocharger projects, projecting an easy 250 hp for "king of the lake" bragging rights.

The Yamaha RX-1 represents an exciting new direction for four stroke snowmobiles. Previous offerings have had many people scared that four stokes would be boring and slow. Thoughts of hoarding two strokes while they are still available had begun to sneak in. Yamaha's RX-1 is redefining the snowmobile and creating new excitement in the sport. The old saying, be careful what you wish for, you actually may get it, applies well to our brainstorming session. In this case we actually got more than we asked for.