2008 Yamaha FX Nytro & Nytro RTX

The all-new 2008 Yamaha FX Nytros are true big-bump, rough trail rider-forward four-strokes. Fitted with a stiff chassis and capable suspensions, the FX Nytro truly brings four-stroke performance to an all-new level. And, they keep getting lighter.

With the introduction of the Yamaha Phazer last year, it became clear that Yamaha could indeed make a viable rider-forward four-stroke sled that was as light as a comparable two-stroke (electric start and reverse). The ergonomics were there, with the rider in the right place to manhandle the sled and better isolated from the bumps. And, the balance was far better for transition riding; where you transition from being seated to standing as conditions required.
Problem was, the Phazer was underpowered for most experienced snowmobilers, despite its high fun factor. 80 HP becomes very rider-weight sensitive, so one immediately had to wonder what would happen if we were to drop a larger engine (or at least one with more power) into its rigid chassis

Logically, since Yamaha had mated a pair of their 250cc four-stroke dirt bike engines to make the 500cc Phazer, why couldn’t they do the same with a couple of 450cc dirt bike engines as well? That’d be one mean 900cc Phazer. Why not?

Yamaha told us they’d already looked at that, and that after the required crank balancing and reinforcement, it would be so close (within a couple of pounds) to the existing three-cylinder Vector engine that it wouldn’t be cost effective to do so.

Bummer. At least it made sense.

Then, when the snocross race season started, we all saw the FX Nytro as a race prototype and the writing was on the wall. It looked very much like a Phazer in construction and design, but it was bigger. Yamaha doesn’t just take an existing chassis and drop in a bigger motor, that wouldn’t be optimum. They took the basic layout and design features of the Phazer, but pretty much ended up with another unique chassis and platform from which to build the FX Nytro family upon.

The engine was bumped up to 1050cc, the max allowed under current snocross rules. EFI was added, along with a host of other detail items to make the Genesis 130 really rip. The engine is likely the strongest part of this sled. The performance is sure to exceed most expectations and should do so reliably and consistently, without being as heavy as the Apex models (an Apex GT dry spec is 560 pounds). In contrast, the dry weight spec of the FX Nytro is now down to 513 (no reverse) and 520-522 with reverse.

The engine lights up with such fast throttle response you can’t help but be impressed with the engine and the torque and the way it pulls your arms, hard. The 130 HP figure doesn’t do justice to the torque this things makes (at least the protos all pulled like a freight train). Remember, the engine got bumped up to 1050cc, and it is faster-revving due to a lighter crankshaft (1.7 pounds lighter than the Genesis 120’s).

It also acts way different than the previous Yamaha four-strokes in that it coasts down easier with an Engine Braking Reduction system – so there’s far less compression braking when you get out of the throttle. We really like this, as it makes the sled way more two-stroke like in its mannerisms.

How’d they do this? It’s in the fuel injection system, surprisingly. A small bypass circuit opens and closes, based on data inputs, to allow some air to pass through and reduce the pressure in the cylinders that cause engine compression braking. It is not adjustable, yet it works amazingly well.

What really jumps out is the throttle response. The calibration of this engine and its running quality has been most impressive in our prototype testing, spot on and crisp and clean, as has been the clutching and gearing set-up. We have no issues here at all. It has 11:1 compression ratio, but is designed to run best on 87 Octane pump gas. The engine itself weighs 10.2 pounds less than the Genesis 120 engine. It delivers all the 4-stroke benefits-fuel efficient, wide power band, reliable, no smoke, no injector oil.

Now realize, the race sled version was used to validate many of the design elements found on the consumer versions, which retain much of the character of a true race sled. There isn’t much in the form of rider protection, much like the “naked” Phazer or Ski-Doo REV models, or any of the race sleds, for that matter, but this nakedness allows you to see what’s out in front of you, and you can really see the ski tips.

Like a race sled, the fuel tank is small; capacity is only 7.4 gallons, and that’s barely a 100 mile range at 15 mpg. And there’s minimal cargo or storage capability out of the box. So logically, this is not the ideal sled for all-day long trail rides. The new RS Vector models that combine the (carbed) Genesis 120 engine into the rider-forward Apex chassis with a re-calibrated Mono Shock RA rear suspension are far better suited for this task.

What the FX Nytro is going to excel at is these two models are the best rough trail sleds Yamaha offers. They don’t go as far as to call them cross country sleds, but they truly do compare to the Polaris Dragon models, the Ski-Doo MX Zs (X-packages and Adrenalines) and the Arctic Cat F-Series, standards and Sno Pros. Yamaha hasn’t really had a sled with this kind of capability for, well, when was the last time? Maybe back to the SX-R? The SX Viper really wasn’t a rough trail sled; that was more of a slot car than a bump sled, despite the suspension calibration.

So when you hop on the FX Nytro, the sensation is one of a bigger Phazer, more so that a trimmed down Vector. Going down the trail it is lighter than a Vector or Apex, but noticeably heavier up front than a Phazer. The FX chassis with sport rider-forward position puts the rider in an aggressive, yet comfortable, forward posture, with the engine down low and back in the chassis. This gives the FX Nytro a very centralized mass. Its CF die cast and tube chassis members make the sled very stiff and very light. The rigidness of the design creates a stable platform for the suspensions to do their work.

Yamaha worked like crazy through the winter getting the suspension calibrations dialed, and each time we rode the FX Nytro models they were getting better and better. The rear suspensions on both models have been quite firm every time we’ve been on them. Not what we’d want to call trail-compliant, but in all fairness we will reserve judgment until we see how the final production calibration performs this fall. For reference, we expect the standard FX Nytro to be very comparable to a (2007) Ski-Doo MX Z Blizzard (or Adrenaline), with the RTX more X-package like.

The handling of the FX Nytro is really quite good, more like a Ski-Doo MX Z than it is a Polaris IQ or Cat F-Series. The IQs and F-Series are all going to have lighter, easier steering, but the Nytro will likely be more precise, like a Ski-Doo would be, generally.

So, if you’re into true rough-trail performance, or the type of riding that consists of ungroomed forest roads, then this is going to be the better suspension calibration match out of the Yamaha line-up. Sit-down trail riders will find greater comfort and compliance in the Apex and Vector models, but those sleds will not be as capable through the rough at higher speeds, nor will they have quite the precise steering or nimble agility afforded by the lighter weight and suspension selection. We can’t go as far as calling it a cross-country sled, as that really would require a 136” or 144” version (2009?) to tackle the deeper snow that category would also consist of.

The 2008 Yamaha FX Nytro retails for $9,999, offered in Team Yamaha blue and white, or a classy white and yellow package. The firmer “Rough Trail” FX Nytro RTX is as close as you can get to the Yamaha Pro Open Race sled. It sells for $10,399 ($10,699 with reverse) and the 40th Anniversary white & red version goes for $10,899.