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Here's the "2008 Showdown in Snowtown," the Polaris 600RR (Race Replica) vs. Yamaha's Nytro RTX (Rough Trail).

Both are similar, if not exact in many respects to the OEM snocross race sleds. The good news is that you can go out and buy either of these at your local dealer! That is, if they aren't sold out already.

I steered both of these hard-core snow-throwers around tight curves, pounded them through relentless stutter bumps and tossed them off every jump I could find side-by-side with our other test riders this spring at our annual test and photo session. Many miles, and photos later, we had a handle on both of these sleds' capabilities.

Roseau is Go-Zone
Roseau, Minn.'s Polaris is throttling into the good graces of many of its skeptics. After a few years of indistinguishable focus, Polaris is doing what's right for itself, dealers and customers. Atop a list of hot '08 sleds is the 600RR.

This is the same 440 IQ race chassis that you've seen Martin, Lavallee, Gulla Eckstrom and the other Polaris snocrossers using to nab checkered flags on weekends for the last 3 years. There are few differences from the race sled.

The 600RR features the same IQ Race suspension, but with a less aggressive shock calibration and softer spring set-up, as well as a standard 1.25-inch RipSaw track, instead of the much larger lugged snocross track. Thankfully, you can feel the less aggressive trail set-up, especially in the rear suspension - the true race machine feels like you're riding a 2x4 through the bumps. But, there's only a small percentage of hard-core riders who would enjoy that sled.

What I like most about the 600RR is that when you step onto it, you feel like a racer. With a 2.5-inch riser standard, and three more optional taller risers, the high, forward standing positioning is most comfortable. You just want to search out a big table-top jump, road approach or anything that will put this sucker up in the air.

This machine screams, "I'm a racer!" There is only a tachometer for gauges, it uses an old school kill switch with no ignition key, no electric start option, no gas gauge, the choke is located down near the top of the gas cell and there's a big tether. Also, instead of the racing gas tank, which only holds 3.2 gallons, the 600RR comes with a 9-gallon tank to permit longer trail rides. You'll get more idler wheels on the 600RR than the true racer too, plus PERC reverse.

Under the Replica's hood is a 599cc liquid 2-stroke, oil-injected, TM-38 carbed Liberty engine. At press time, gearing was not final, but Polaris tells us the RR will be geared down for acceleration, not top speed. Don't let this modest 600 fool you; in our pre-season testing it was super snappy and had long legs.

We all agreed we'd spend the little extra and get the slightly taller accessory windshield and hand guards, which provide at least some protection from the elements. While some may debate me, I found this sled comfortable in the trails. I tend to stand often though, and most sit-down Harley enthusiasts could consider the handlebars ape-hangers.

With an estimated dry weight of 475 lbs., the sled has become beefier than its original 445 lb. racer weight, but even with the extra pounds, it sits on the lighter side of the 600cc scale. While it's not as light as the new Ski-Doo 600 XP Adrenaline at 428 lbs., it's lighter than Yamaha's Nytro at 520 lbs. During testing, it was excitingly easy to launch the 600RR off snow banks and push it hard through huge, straight moguls.

Polaris 600RR
Engine: Liberty Liquid twin TM-38 carbed 599cc, 2-stroke
HP: 120
Exhaust: SC VES, Single
Ski Stance: 42.5 in.
Front Susp.: IQ Race w/Walker Evans IFP 16 pos. comp. adj. remote reservoir shocks
Rear Susp.: IQ Race w/Walker Evans aluminum springless front shock and Walker Evans IFP 16 pos. comp. adj. remote reservoir rear shock
Track: 15x121x1.25 in. RipSaw
Fuel Tank: 9 gal.
Dry Weight: 475 lbs.
2008 MSRP: $10,299 US/$13,299 CA

Yee-ha for Yamaha
What do you say when you straddle 138 horses at once and take hold of the reigns? Yeeeeee-ha!

As you saw earlier in this issue's dyno test story, (p. 18), those horses pull like Clydesdales, and the new liquid fuel-injected 3-cylinder, 4-stroke Genesis 130 puts power to the snow like no other sled in its 130-140 hp class.

Like all of Yamaha's new 4-strokes, the high point of this sled is under the hood. Bore and stroke on the 1050cc Nytro equal 82 mm and 66.2 mm respectively, and the whole engine package is situated low and angled back 37 degrees in the chassis in order to centralize the mass. You really feel the full effect of this engine on takeoff - the holeshot is incredible! Robbie Malinoski proved this numerous times on the WPSA National Snocross Tour last year by often getting phenomenal starts and making passes coming out of corners.

The sled Robbie and teammate Yuji Nakazawa rode last season was a direct decendent of prototypes Yamaha tested at chosen snocross races. We saw one prototype code-named M160 - admittedly more older Vector than new Nytro - at the 2006 Eagle River Derby. From these tests, Yamaha engineers were able to slice 22 lbs. from last year's stock Vector-based Nytro for the new Nytro.

Weight was cut in many ways including adding more Controlled Flow die-cast pieces like the chaincase, and using strong, lightweight plastics for things like the headlight and radiator mounts.

The snocross influence on Nytro RTX is obvious in the rider position. The bottom of the riser sits almost directly over the radiator, and if you drew a line straight down from the top of the gas tank to the bottom of the sled, you could probably balance the whole machine on that point. Extra-wide running boards provide excellent traction, but only decent snow removal. While the snocross inspired windshield gives zero wind deflection, the hand guards are larger, stronger and provide more debris protection than on other OEM machines. You'll find the seat comfortable and easy to move around on.

Like Phazer, Nytro has a single rear exhaust. The 3-1 exhaust runs under the seat and has a throaty 4-stroke tone.

Under the seat, exhaust and tunnel, lies a Dual Shock Pro rear suspension that is better than any stock Yamaha suspension before. Its controlled transfer is impressive. You can set this suspension to pick up the skis easily, but it won't feel like you're doing a full wheelie on a dirt bike. Its two 40 mm dual-clicker shocks allow you to adjust rebound and compression on the front and rear arms. With 11 compression and 18 rebound settings, there's a big range of set-ups. You can adjust the limiter strap and center shock spring preload too.

Yamaha Nytro RTX
Engine: 1049cc fuel injected 3-cylinder, 4-stroke
HP: 138.6
Exhaust: 3-1 rear exiting
Ski Stance: 41.3 in.
Front Susp.: Independent double-wishbone w/Fox Float shocks
Rear Susp.: Dual Shock Pro w/40 mm HPG remote res., dual clicker center shock and 40 mm HPG remote res., dual clicker rear shock
Track: 15x121x1.25 in. Camo. RipSaw
Fuel Tank: 7.4 gal.
Dry Weight: 520 lbs.
2008 MSRP: $10,399 US

Side-by-side
Both sleds do some things superbly.

The Polaris 600RR has possibly the best big-bump and hang-time abilities of any sled this year. I am more comfortable standing on this machine than I am on any other stock sled out there. This is the ultimate freestyling fun machine that you can buy direct from your dealer. The power from this simple carbed 600 is impressive, usable and perfect for the chassis. I was comfortable on and off the trail.

Yamaha's Nytro RTX has the best new engine of the year. It's not the most powerful, but it is a rocket from a stop. Much of this is due to its new lightweight crank design and spot-on fuel injection system. Nytro never quits pulling. The sled has all the quality you expect from Yamaha, less weight than its predecessor and more horses. With 18 hp more than the RR, the Nytro has more top end, but surprisingly, in unofficial flatland speed tests and hillclimbs, the Nytro did not pull away from the 600RR by more than one sled length in about 600 and 500 feet, respectively. Possibly the best news is that both of these sleds run best on 87 octane gas.

Now, the bad news. With a 9-gallon tank, the 600RR will have a limited range, especially considering that those who ride it are most likely to have a heavy thumb. It's true that the Nytro has a smaller tank at 7.4 gallons, but mileage will be much better. I also found the Nytro RTX more difficult to keep at a comfortably fast speed though while still maintaining ski bite in stutter bumps in the corners.

Adjusting the suspension correctly on both of these sleds takes some skill - especially on the Yamaha - and would not be recommended for the average Joe. Both have tall shock towers and plenty of clearance though, so you won't ever dig the front end in.

While Yamaha added an Engine Braking Reduction System to allow the sled to "coast" more when you let off the gas, engine braking is still more pronounced than on most 2-strokes. Both sleds are cold to ride in frigid temps and wouldn't be good high-mileage ma-chines, but that's not their intent.

I'm also less impressed with the 600RR's overall quality compared to the Nytro. But, both of these sleds can take a beating. I have seen both rolled, and I've even seen the Nytro slammed upside down into a tree after rolling down a mountainside, only to get pulled out without so much as an emblem missing. Both sleds started right back up and weren't any the worse for wear.

At the end of the day I feel I can toss the 600RR around a bit better than the Nytro. Besides, a big part of my personality sways toward the 600RR because like many self-proclaimed wanna-bees, I want to at least look the part of a snocrosser. Also, there is just something about being one of a precious few with a limited build sled. Unless you snow-checked an RR, you probably won't get your hands on one.

However, looking down the road, I might want a more trail-friendly, quality, machine with an engine that will outlast any 2-stroker, AND run with the 800s. Throwing down the extra $400 for a Nytro RTX would most likely be worth it. Either way, I don't think I would be disappointed when the snow hits.

OTHER'S COMMENTS

600RR:
Jerry Bassett - The biggest surprise of the sled tests. I was expecting a rough, stiff racer and found a supple and nimble sports sled with a wonderful personality for banging off-trail. Nice power, and Polaris engineers worked wonders in combining a racer and trail-friendly big bump technology. Great foot placement, extremely easy to ride and an absolute hoot on or off the trail. Well done!

Nytro:
Bassett - When first ridden at the Yamaha "sneak peek" in January, the Nytro was all about power, but it was short on handling. That was changed for my second ride at the "official" review out West. This time the front end stayed on the snow, and weight transfer, which had been more suitable for grass drag racing, was now under control. Steering was improved, and the Nytro is comparable to the '07 Ski-Doo REVs, but seems heavy vs. the improved 2008 REV-XP.

POWER-TO-WEIGHT RATIOS*
Yamaha Nytro RTX - .266 hp/lb.
Polaris 600RR - .253 hp/lb.
* Independent AmSnow/Dynoport tested hp numbers used with manufacturer dry weights.