4-Stroke Fast

Time to stretch!
2019 Yamaha SRX LE
If you are an aggressive rider, and over the age of 40 like me, you should probably be doing some warm-up exercises before every ride. But that’s not the kind of stretching we’re talking about here. The manufacturers have gone longer in track size for all sleds, but most interesting to me is the small sub-category of Super 4-stroke Sleds. These are all stretched out to 137-inch crossover lengths, but are marketed more as trail sleds and do-it-yourself lake racers. These are namely the Yamaha SRX LE, the Arctic Cat ZR 9000 Thundercat with iAct and the Ski-Doo Renegade X-RS 900 ACE Turbo.

■ Yamaha SRX LE
The Yamaha SRX name is iconic and brings back fond memories of the smell of 700cc 2-stroke river racers that we had in the early 2000s. Folks reporting on this sled have all claimed that it is built for one thing only: speed! I would disagree. This sled is made for speed plus comfort, handling and reliability.

Yes, this sled has the 998 Genesis one liter fuel injected motor, and of course it has the turbo along with triple throttle body induction and seemingly zero lag when you jam the throttle to the bar. And yes, this sled has been clocked by AmSnow well above triple digits many times. Also, it is true that this sled is lowered this year and receives new dual rate front shock springs and low preload torsion springs in the rear end to give it a lower ride height for more aerodynamics. But hey, that’s not all necessarily for speed.

Honestly, it is the fastest stock sled on the snow, but the new Fox iQS shock package that can be adjusted on the fly from the handlebars gives this super sled a level of comfort not found on any monster lake-racing sleds of the past. This is the same system as the iAct on the Arctic Cat sleds and it offers compression damping in three levels (soft, medium, firm). In combination with the dual rate springs up front and adjusted ride-height, this sled hugs the turns, and is still extremely capable in bumps of almost any size. This is not meant to be a snocross sled though, so going through five-foot moguls at 60 mph is still not advisable. But the progressive rate on the springs resists bottoming and even on the medium setting on the toggle for the Fox iQS adjustable suspension, you can barrel through pretty formidable bumps.
2019 Yamaha SRX LE
The 137 is the correct length for the Sidewinder and with the 1.0-inch lug on the Ripsaw track you can really reach some crazy speeds. It is also easier to negotiate tight corners or drift/slide the corners with this smaller lug. Of course, that would not necessarily be the case with the stud packages we are certain many consumers are going to want on this sled. But that 137-inch length also smooths this sled out and the balance and handling of such a big 4-stroke is impressive. Chalk that up to the SRV triangulated chassis structure. Gone are the days of wrestling a Yamaha 4-stroke in the corners. This one has a straight steering post configured over the engine and the sled can turn much sharper, with much more precision and predictability than past 4-strokes.

Let’s get back to the comfort and reliability factors. You get a heated seat on this sled plus new Stealth handlebar controls. These controls contain the cluster that has the on-the-fly adjustability of the suspension, hand/thumb warmers and new push-button reverse. There’s also a new shorter Hayes brake lever and newly reinforced cylinder. Oh, and finally, this is a Yamaha 4-stroke, which means long-lasting reliability from the best 4-stroke engine builders in the industry.

This wasn’t our Best of The Best 4-stroke sled this year for nothing!

■ Arctic Cat Thundercat with iAct
This sled might have totally different colors and show a few small changes here and there, but it is similar to the Yamaha SRX LE. Differences include small changes in windshield design and other things, but primarily the difference is in the clutching. Yamaha uses its YSRC clutching and Cat uses an auto-adjusting drive clutch and their lightweight driven clutch. These sleds are pretty close in many aspects, but we think the clutching from Yamaha is slightly better.
2019 Arctic Cat ZR 9000 Thundercat with iAct
However, we liked additional aspects not mentioned above, such as the fact that the Thundercat has the ProCross 6 skis that really dig in on the trail, and the adjustable 42-43 inch ski stance. Some folks we know like to move those skis for drag racing on the lakes, depending on conditions.

The Thundercat still has the slide-action rear skid with the 3-wheel rear axle assembly. We absolutely recommend putting the 4th wheel kit on this sled or the SRX, especially if you are studding them. The durability and longevity increases and the power that these sleds put to the snow is just incredible. At an estimated 603 pounds dry-weight, these are not super-light sleds either, but they certainly are built to last.

The iAct shock system utilizes Fox 1.5 Zero iQS shocks up front and a Fox 2.0 Zero iQS shock in the rear. The center Cat IFP 1.5 shock is not part of the adjustable system, only the fronts and the rear. This is the same on the SRX, and we have mentioned before that we expect the center shock to also be adjustable for next model year sleds.
2019 Arctic Cat ZR 9000 Thundercat with iAct
We can’t say how much we enjoy two features about both the new Thundercat and the new SRX: having a tether and push-button reverse standard. Those two additions for safety and ease of use are worth every penny.

The 11-inch mid-height windshield and 5.5-inch standard riser work well together. You can tuck in behind this shield, and with the seat and ergos of the panels you can really get out of the wind on this sled, especially if you are a shorter rider. We would absolutely suggest some pretty serious handguards though, not the fly-screen ones that come standard. Otherwise, you will be cruising at faster speeds than you even realized at some point and will start to wonder why your hands are freezing. It turns out cruising at 80+mph is pretty easy behind this sled!
2019 Ski-Doo Renegade X-RS 900 ACE Turbo
■ Ski-Doo Renegade X-RS 900 ACE Turbo
We talked plenty about the new 900 ACE Turbo motor in our October Issue (check out the exclusive dyno test and Tech Notes) but this sled is really the first 4-stroke that comes close to taming the biggest bumps on the trail. It is not quite Snocross ready, but it is made to sit higher, have more clearance, fly farther and smack bigger bumps on their face. Oh, and be pretty fast as well.

At 162.8 independently verified horsepower, this sled plays right in the top end of the 800cc twin power range. But it is a 4-stroke, so it is a much more linear power band. Sitting in the much more rough-trail-focused X-RS chassis, this makes for an interesting ride. Kind of like putting a Cadillac Northstar engine in a Camaro. Not terrible at all; kind of interesting and just different.
2019 Ski-Doo Renegade X-RS 900 ACE Turbo
Ski-Doo also left the smaller “rotating” throttle flipper on this sled. We kind of scratched our heads at that because this lever is known to get caught in folks’ gloves due to its small size, and since this is throttle by wire it is often hard to tell exactly how much gas you are giving the sled. Finally, we do not know of any rough trail riders who would feel comfortable turning the throttle around to be a finger throttle, while riding through a seriously rough stretch. All that being said, you won’t ever have a sore hand after a day of squeezing this lever!

The X-RS has the new wide body design and on the whole it looks incredibly tough. Hats off to the design team here. The RAS 3 front end is wonderful with the KYB easy adjust compression/rebound dialing remote reservoir re-buildable shocks. We are also huge fans of the running boards on this sled with lots of room to move around and great snow evacuation.

The rMotion rear suspension is really what allows this sled to go to the next level over the more lake and groomed trail-focused SRX and Thundercat. With KYB Pro 36 R front shocks and KYB Pro 40 rear shocks aluminum piggyback with Easy-Adjust compression adjuster (22 clicks), this sled lands soft even on big hits. Plus, it is playful where most sleds of the 4-stroke variety (lighter 544 lb. dry weight) tend to get a little squirrely.
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