1998 formula z 670

The Bombardier folks keep working the angles. They have taken the fundamental S-2000 aluminum chassis, used for virtually all twin cylinder models, and created multiple personalities for it. There's the set of fan-cooled touring sleighs. And, of course, there's the hot yellow mogul mashers in MX Z trim.But, for the Bomber faithful, there's a sled that truly puts the grand in sports- the Formula Z 670.

With the time-tested and beloved 669cc rotary-valved twin pumping out115-plus horsepower, this grand sports machine assures its owner of steady grunt where you want it- low end and midrange. Top speed will be respectable as well. The grunt comes from a two-into-one manifold dumping into a single tuned muffler. Equipped with Rotax' mechanical exhaust port modifiers, the liquid-cooled twin masters low end and upper end performance from initial to peak revs. Dual 40mm Mikuni carbs suck 87 octane fuel from the F-Z's standard 10.6 U.S. gallon gas tank.

Our test riders historically have been impressed with the Rotax 670 series twin. This new Formula Z repeats history as our test riders rated the engine/clutch combination strongly and felt that throttle response was good. Of course,when cranking on a pair of 40mm slides, the throttle feels heavier than if it were an injected sled or Yamaha's rack-assisted flat slide carbs.This is where the dual action throttle helps. Up to half throttle the pull is light, stiffening from there to wide open.

At wide open we found the F-Z could crank out an observed top speed of 82 miles per hour in sloppy snow at our western Idaho test site. That compares with a same day, same location observation of the Formula III 600 which hit 76.8 mph.

But speed isn't what this sled is about. It's about comfort and agility,supposedly what sports and solo cruising riders want. That's why Bombardier opted to add a new concept rear suspension instead of an updated SC-10.The new rear suspension was conceived by the Brothers Boivin, who offer their own "Expert" design as an aftermarket retro-fit.

In comparison to the similar, but SC-10 high performance equipped Formula 583 Deluxe, the Formula Z 670 offers an inch more vertical travel. Both rides are controlled by one of Ski-Doo's Motion Control gas shocks on the front and rear suspension arms. Providing a smoother ride and better control is the basic idea behind the new F-Z suspension. You'll notice the much longer front swing arm which is mounted at a less severe angle than on other rear suspension designs. The thought is that it will result in smoother,less aggressive take-offs and provide more controlled transfer when accelerating out of turns.

The swing arm design also regulates weight onto the suspension's hyfax while distributing load equally for maximum traction at virtually all speeds.

The front suspension is standard modern Ski-Doo trailing arm fare with gas shock control and 7.7 inches of travel. The 42-inch ski stance definitely helps maintain stability as our test riders noticed.

Test rider Doug Erickson found the new Ski-Doo to be very interesting,noting, "Due to the single pivot point for the suspension, there is little, if any, weight transfer both in acceleration or deceleration. With that in mind, it didn't accelerate as quickly as the MX Z 670 with the SC-10 cross country setup.

"What I really liked about the new Formula Z suspension was that it kept the front end planted in most conditions. Whether under hard acceleration coming out of corners or riding over choppy bumps, the skis stayed firmly on the ground. It worked quite well in marginal to average conditions on the snow.

"Where it has its downfalls is in extreme conditions, deep ruts,that type of thing. It would bottom out first. If Ski-Doo has intended this sled to be used on primarily groomed trails and as a comfortable sports touring sled, then I think it will do a wonderful job. However, in extreme conditions it is certainly going to be out classed by the MX Z series.

"The steering on the F-Z 670 with the new suspension is very preciseand very confident. There wasn't any pushing in the corners. When you turned it, it went where it was supposed to. I thought it was the best of all of the Ski-Doos I rode, especially when accelerating."

With the new suspension and the inclusion of the bigger twin, Bombardier plays the angles to give its Ski-Doo customers another option in the sports sled category. There's more power than what you'll get with the Formula583 and stouter performance than any other "Z" model except the triple cylinder Formula III 700. But there's a ride option to consider,and as test rider Erickson noted, it is quite different than the standard SC-10, whether in the mogul masher class of the MX Z or the softer rideof the Formula Z 583. Our experience with this suspension is very limited.We will be getting a unit for long term testing, but as of now, all we can give you is some semblance of a first-impression opinion. The concept makes sense. We'll have a better read on the execution in a 1,000 miles of longterm testing.

We can tell you that the basics of this sled are very sound. The S-2000 chassis has been a hit since it was first developed for the Formula SL and fan-cooled touring models three seasons ago. Throw in a very nicely controlled Brembo hydraulic disc braking unit and you have a sports sled with very good balance of go and whoa power.

If we owned a F-Z 670, we'd opt for a taller windshield. The low one looks sexy as heck in the showroom, but the mid-height wind screen keeps you warm.

That's about our only real complaint with Ski-Doo's new grand sports.After all, how we can do anything but giggle when it comes to a sled with a powertrain we enjoy, a style that's appealing and a suspension approach that's new?