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December 30, 2010
Project CHR: Canyons, Hillsides and Ridges
Building the perfect sled for our favorite kind of riding
Sometimes, normal can seem so odd.
Normally, we follow a regular rotation in our project sled builds. This past season, we broke the chain and hand-picked a 2010 Arctic Cat M8—the hottest 800-class mountain sled of the season.
Normally, we team up with a renowned dealership or sled builder to handle the construction in a controlled in environment. This time, we built the sled from the ground up on-site at the Intermountain Snowmobile Show in Salt Lake City, UT.
Normally, we build a sled that follows the hottest and newest trends of the market. This time, we built the machine the way we wanted it—going back to the basics of a lightweight, great-handling sled with just a little extra power. And we even took a few steps back in history (nitrous) to get the performance we were after.
Normally we’d be almost in over our heads on a machine built for those Thunderstruck-style chutes and bowls. This time, we were on a machine purpose-built for tree-covered, off-camber, nasty V-bottomed canyons covered in grainy snow that sees about as much sunlight as it sees blown-and-boosted chute rockets. And we were right at home.
How To Build The Perfect Tree Sled
In our book, there are three big factors for anyone to consider when setting out to convert a stock sled into a worthy backcountry mod: 1) reliability, 2) weight and 3) handling.
Power matters, but not as much as those three. Ski-packing horsepower is worthless if it’s a hassle to keep running, tires you out before the ride is over and is a chore to control. Weight lost is equal to power added and it has the added benefit of making the sled easier to control.
Being Towed Stinks
When we mapped out Project CHR on paper, those three points were our priorities. Nothing ruins your outlook on the sport quicker than seeing a machine you’ve dumped thousands of dollars into suddenly turn become a piece of furniture. We wanted to avoid breakdowns and tow incidents at all costs. Project CHR was towed off the mountain once when the throttle stuck open. But that turned out to be a piece of tree branch that had poked through the intake screen, bounced down the intake plenum, into the air box and managed to get wedged in the mag-side throttle body (tree riding has its risks, apparently). Otherwise, Project CHR proved as reliable as a stock sled.
We had a big goal in mind for weight reduction: take 40 lbs. off the M8. How did we do? When the snow settled on our final rides, we had removed 35 lbs. of dead weight from the sled. That’s 35 lbs. we didn’t have to lift out of holes, hold up on sidehills or control on downhill turnouts. It’s like being able to open the hood and pull out seven 5-pound sacks of potatoes and toss them aside. That’s a big muff pot.
Where’d the weight come off? These products saved weight by the pounds: C3 Composites carbon fiber hood, HPS can (first) and SLP exhaust system (later), EZ Ryde rear suspension, Fox Float R Evol air shocks, super-trick Diamond S titanium A-arms, Black Diamond Xtreme Diamond Lite Drive and drive shaft, throttle bodies and brake rotor and RCS Rasmussen Signature Series titanium coil springs in the rear suspension.
With the hood, we deleted the gauges (we used the Dynojet Wide Band 2 with Power Commander III digital display instead) and headlight. When we added weight, we used the lightest parts available. The Boondocker nitrous bottle is the lightweight 4-pound carbon/glass wrap bottle. We gave the SLP Powder Pros the hillclimb trim, cut out from the stock foot beds as much material as we added back in with the Better Boards and stayed neutral with the WRP Assault seat, SLP side panel vents and air box mod and RSI Racing handlebars.
There’s more weight on the sled that could come off fairly easily, especially now where product availability for the 2010 M8 has improved.
What is handling and what makes it good? There are lots of ways to get an idea of good verses bad handling traits. Would you rather do 80 mph in a sports car or a box van? Would you rather take a downhill dirt trail on a full-suspension mountain bike or a 10-speed road bike?
Handling is indirectly affected by things like rider position, sprung weight, unsprung weight and geometry. Handling is directly affected by suspension design, shock absorber technology and anything that touches the ground. We improved Project CHR’s handling—and we’re talking how well it handles and responds to rider input on sidehills, tight trees and progressive-style riding—by changing the stock Float rear suspension out for the EZ-Ryde rear skid, by changing the front skis shocks out to Fox Float Evol R shocks and changing the skis to SLP Powder Pros.
Now it’s time to get into the power adders. Sure, you could start out by adding power and skip everything we’ve done so far. But now any power we add will be magnified drastically by the weight reduction. If you’re wondering why we chose to go with nitrous, that should explain it. It’s reliable (Boondocker’s dry induction nitrous system is proven safe on high-performance two-stroke engines) and we’ve managed to avoid so much as removing the head. The internals of the engine are untouched from the factory. And given Arctic Cat’s strong track record with its M8 800 twin engine, we’re confident in the stock engine’s durability. And running Royal Purple Snow-2C oil was added protection in our minds.
The Boondocker nitrous kit doesn’t add too much weight back onto the sled, either. There may be more ways to get the same power without adding any weight at all, but that leads to internals and breaks our first rule with this sled. And there are ways to add a whole lot more power if we’re not concerned with weight, like a turbo kit. But the Boondocker nitrous kit’s adjustable regulator setup offers anywhere from 10 to 70 added horsepower—more than enough for what we needed the sled to do.
The Boondocker nitrous couldn’t have been easier to use. Once everything was installed, we went to the Boondocker control box and set the system to activate automatically at wide-open throttle. Say the throttle position has a range from 0 (closed) to 75 (wide-open). You simply go in and set the system to activate nitrous on TPS at 70. From then on, you only need to worry about refilling the nitrous bottle. With that setting, we could back off the throttle enough to shut off nitrous delivery without affecting engine speed (as in, the engine is still running at full-throttle without nitrous). You can also manually activate the nitrous system with a push button mounted on the handlebars.
With this setup, we were able to get though a day’s ride on about 7 lbs. of nitrous, using a lightweight carbon-wrap bottle.
Another source of extra ponies came from the Starting Line Products M8 exhaust system, which gave the M8 about a sled-length jump on a stock M8 and dropped about 18 lbs. from the sled.
The Black Diamond Xtreme 50mm lightweight throttle bodies gave the engine improved throttle response without compromising anywhere else.
We absolutely hammered this sled through hillsides covered with thick trees. We dropped over ridges that we normally avoided because the bottom seemed like the kind of place you’d be setting up camp for the night. But with Project CHR’s light weight, ease of handling and added power, we could drop in, play around and carve our way back out. We did our best to abuse it and were always surprised to get back to the trailer and find everything still attached. Even the SledWraps custom hood wrap made it through the season unscathed despite rubbing against trees and branches so hard that we were popping out intake vents and windshield rivets.
On more than one ride, Project CHR proved to be a surprise to a few pump-gas turbo guys in the group. It would take a little more effort and creativity, working the hill rather than just blasting straight up it. But the look on the faces of the turbo guys was priceless as they were met with a non-boosted sled just about everywhere they tried to go.
There’s nothing normal about our entire process behind Project CHR. And oddly enough, it’s quite possibly the best project sled we’ve ever built.
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