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Ski-Doo's new QRS secondary clutch is quite an advancement for the snowmobile industry and it shows that Ski-Doo engineers are "thinking outside the box." But, such change means we must re-think how we swap out a clutch and clutch components.
The first notable design difference is that you can't just unbolt the clutch from the jackshaft. That's because one of the clutch sheaves is cast directly to the jackshaft, and the other is simply slipped over it instead of using the standard clutch hub.
Yet, the new secondary system has two extremely positive attributes. First, it's a lot lighter. Second, it now has a double-supported movable sheave.
Its light weight was achieved by using a hollow hydroformed tube and fusion welding the gear spline hub to the end, thus having a totally hollow jackshaft. The one movable sheave is now directly bolted to the helix, creating a more supportive movement with less stress on the clutch and bushings. When a movable sheave and the helix are bolted together, the amount of sheave movement back and forth is almost eliminated producing better belt and bushing life, and more precise clutch shifting.
QRS clutch/jackshaft removalRemoving the jackshaft assembly is fairly easy. Here are a few easy steps:
• Step One: Remove the belt, and the belt adjuster. Using your supplied tools from the sled, insert the clutch tool into the center of the belt adjuster and loosen the center nut three turns. Insert the belt adjuster tool and compress the clutch until you are able to remove the belt. After belt removal, completely unscrew the adjuster and remove. Unbolt the gold bearing keeper support just behind the clutch itself.
• Step Two: Remove the rubber cover on the top side of the chaincase. Unbolt the top gear through the hole and be sure not to drop the bolt and washer.
• Step Three: You'll need to push the clutch out through the left side of the sled. Completely push the shaft through the jackshaft bearing support tower. Do this by putting pressure and possibly slightly tapping on the chaincase side of the jackshaft. As you push the clutch out of the chaincase, the top gear, spacer and chain will not be supported anymore and will fall to the bottom of the case. To avoid this, put a screwdriver down the center of the threads and leave it there to hold the components during removal. Ski-Doo has a tool specifically designed to hold these items during removal too. (Part No. 529 036 110, price $28)
After removal, you'll notice the system's extremely light weight assembly compared to a traditional clutch and jackshaft.
Clutch helix removal/new installTo remove the helix, a helix compressor tool is required.
• Step One: Insert the tool into the threaded end of the jackshaft and then add the plastic spacer and washer from the tool. Thread the handle onto the tool and screw down to compress the spring.
• Step Two: After the spring is compressed, you can remove the 4 bolts holding the helix to the movable sheave. On your first removal, an impact driver is typically required to break the bolts loose.
• Step Three: After removing the bolts, unscrew the tool and the helix and the spring will come out with ease. The base of the fixed sheave and the helix has a nylon spacer in it. Removing the nylon from the bottom of the helix may require a pick to get it out. Remove the spacer and install into the new helix.
• Step Four: The new helix can only be installed one way, notice the cutouts across from each other. The shallower cutout in the helix will be installed into the rollers. Installing the helix incorrectly will cause severe damage to the clutch and helix. When installing the new helix and spring, be sure to use Blue Lock Tight to keep the bolts from coming loose. Align the sheaves using the arrows casted into each side of the sheaves. When fully assembled the arrows should line up.
QRS clutch/jackshaft install tipsInstalling the full assembly is pretty much a reverse of the removal, but here are a few tips to keep in mind:
• Tip One: The most important thing to remember is that when sliding the shaft through the bearing housing and into the chaincase, DO NOT drop the chain, gear and spacer or you'll add a ton of time and difficulty to the process. To make sure you don't drop them as you're installing the shaft, put the screwdriver into the bolt hole and keep it there until the gear splines are lined up and pushed in. Also, when aligning the splines, you may have to rock the shaft back and forth to help alignment. A typical installation requires two people.
• Tip Two: You may not be able to push the clutch side bearing all the way into the housing because there is a small amount of press-fit between the bearing and housing. To remedy this, simply install the gear bolt and begin tightening. The bearing will pull itself into the housing. Also, make sure you have no binding during the install. If your bearing starts to bind, apply a small amount of lube inside the housing. This helps smooth the installation.
• Tip Three: When installing the bearing keeper and belt adjuster, set your belt tension and lock the center nut three turns.
Your first time through removing and installing the clutch may take some time, but as you continue to adjust and change the QRS, you'll see that it's fairly simple; it just may take longer to make changes than on previous models.
QRS tuningSki-Doo's new clutch assembly is a big change, but it still possesses all the tunability of any previous clutches. Helixes and springs are still available for tuning the QRS system. The same springs available for the RER button and RER roller clutches are standard items for the QRS. There are many springs available for self-tuners from Ski-Doo and aftermarket shops, including mine, Straightline Performance.
QRS helixes are full cast helixes with one angle pre-cast into the mold from Ski-Doo. Straightline's QRS helixes are machined from 6061 billet aluminum and are available in most common angles. Typical ski-doo helix's on the stock 08-09 machines are small progressive or straight angle cuts. Ski-doo helix's can range from straight 44, straight 42, and short progressives angles like 42/40 and 44/47.
Clutch tuning is no different than in earlier Ski-Doo models as all the same theories apply.
Compared to stock helixes, we see advantages to aftermarket replacements, like Straightline's new 2-piece billet helix. The new 2-piece helix allows the consumer to buy the cover and helix separately saving up to $50 on all following helixes. This is a significant amount of money when buying several new helixes to test.
Cast helixes also can have larger tolerances than a fully machined part. Cast parts go through contraction and expansion during production. Hence, the material changes have tolerances to work within and are suitable for production machines.
Straightline's new cover and helix assembly allows the user to buy a cover and then individually buy just the base helixes. Using the 2-piece helix, you can just buy a helix angle without a complete helix. The new cover also allows for the use of a torsional spring to produce a torsional load as well as a compression load. During a shift, the spring rate changes at a more precise speed having two loads applied on the helix. Using both forces makes the clutch shifting more repeatable and consistent.
New CVTsToday's continuously variable transmissions with clutches like the QRS still have the same theories as CVTs of the past, but they have improved the percent of horsepower transferred through them with improved geometry, more precise machining and support characteristics. These advantages produce less slippage and belt heat, which means more horsepower to the ground.
With weight loss, EPA guidelines, engine efficiency and other concerns being the focus of much of the current snowmobile technology, there still have been improvements with the CVT system helping to move the machines to the next level.
Is there anything left to be improved? Can it be any lighter?
I get these questions daily, and the answer is yes. With the constant research and development being done, we will soon be asking ourselves again, how did we ever ride those old machines?
Jason Houle owns Straightline Performance in Forest Lake, Minn. For more info on this topic, or Straightline's products, visit www.straightlineperformance.com.