Snowmobile Inspection – Idler Wheel Check
As a snowmobile owner, one is expected to be able to keep track of and be aware of some simple service items to keep your sled running smoothly. The most basic is to fill the gas and oil tanks before operation. One should also watch the coolant level of the sled, maybe not daily but frequently so you will know if there is a leak or reason for the level to be dropping.
Mechanically, one should be paying close attention to the condition of the carbide runners on the skis and the hyfax wear strips on the suspension rails. These are far more critical early and late season, requiring daily inspection at times, but in the middle of the season they can last for months and months with little wear. It’s all about the snow, how much, how hard it is and how loose it is.
The condition and fit of the CVT drive belt is a critical item, as the drive belt does wear and stretch slightly over time, and is subject to damage from episodes such as a frozen track or parking brake being engaged. In these cases the primary clutch squeezes the drive belt but the secondary clutch is locked in place. If this condition continues for more than a few moments, the primary clutch can burn a notch into the drive belt, narrowing the belt width in that specific location that was squeezed and burned away during the moments of operator ignorance.
One especially wants to pay attention to the drive belt tension, or slack, which can be adjusted with the secondary clutch and ride height (how high the belt sits in the rear clutch when stationary). Generally, when the belt wears it narrows in width, causing it to drop down into the secondary clutch and reduce the tension.
While most snowmobile manufacturers have reduced the number of grease fittings in the suspensions, there are still a few in every sled that do require you to fill them with grease and push the water out of the tubes. Not only to keep the shaft moving freely inside the tubes, but to also displace the water and to prevent corrosion.
You should also be keenly aware of the condition of your track. You need to know your track is safe for use at high speeds, much like the tires on your truck or trailer. Through normal use a track can wear out, like a tire. Perform a full-rotation inspection as needed, at least once per season. Ideally, do this at the end of the riding season so you can also relieve the track tension during storage. Look for weathering, cracking and dry-rotting as the rubber will degrade through the years of use and wear, along with UV exposure. Tracks can also be damaged from catching or contacting a solid object while spinning, so look for torn lugs or damaged belting. And finally, don’t just look on the outside of the track, also perform a full-rotation inspection of the drive lugs on the inside of the track. Damaged or missing lugs on the drive side are also reason for alarm and concern. Replace your track immediately if damage is found, as it is your critical connection to the snow.
Now we get to our most often ignored items, the idler wheels. You want to be keeping an eye on the spinning idler wheels in your rear suspension. Not only the condition of the wheel and the rubber, but the condition of the bearing. Even today, it seems this is one area that sleds continue to suffer component failure as these wheels live a tortured existence in water, ice and snow, getting hot (and expanding) followed by getting cold (and contracting). This process, repeated many times, tends to suck water in past the seals which leads to the bearings turning harder and eventually losing their lubrication, leading to corrosion and the fatal lock-up.
During a routine inspection, not only look at the rubber on the idler wheel for wear or delamination but give them a spin. See if they are tight and quiet, or are they loose and noisy. The bearings, dummy. It used to be where we would pull the seals, clean the bearings, repack them with grease and reinstall the seals. Seems these days we’re more apt to save the time and simply install new bearings, preferably higher quality pieces to prevent this from being an issue so often.
When it comes to selecting replacement bearings, you can find cheap replacements all over the place but will be getting bearings not best suited for the winter severe use application. Some riders like to use the NTN Formula (blue seal) bearings, others have found they have far less frequent problems with the Ski-Doo sleds and the exclusive NSK bearings they feature. You can get many of the common sizes found on Polaris and Arctic Cat sleds in the NSK line. The NTN blues will often last for (about) three years or 5,000 miles of rough riding and the NSKs will often last even longer.
You can look up the OEM number on a parts catalog, then cross reference it to the 6000-series number for ordering purposes. The ones used on the small idlers in the Polaris skid are a 6004 size bearing, Polaris #3514384, which is a Ski-Doo #503190396 to get the really good NSK ones. The OEM Polaris idler bearings do seem to go bad quite often. Many of the others are a #6205 bearing, Ski-Doo #293350115. These are unique specification NSK bearings that are exclusive to Ski-Doo, and can not be sold by NSK to the aftermarket.
It seems Polaris (for a period of time, at least) might have been using one type of bearing during assembly and then switched over to a better quality bearing for their parts supply. They probably found out their supplier was sending them parts that weren’t good enough, so the next “batch” was better. While not totally uncommon, it is kind of a bummer to think the sled was built with cheaper parts and then when you go to replace the cheap parts you are having to pay (again) to get higher quality parts. Makes one wonder.
This simply demonstrates part of the vicious cycle of the OEMs always trying to reduce production costs, then finding the parts they’re getting have dropped in quality, then having to go back and spend a bit more for better parts, and the cycle continues. If it makes you feel any better, Polaris has told us that for the 2020 build they will be using more durable idler wheels and bearings in an attempt to provide greater durability in this area. Thus, we would also expect the spare parts inventory to switch over to the “new” parts. Sometimes a new part number is assigned, sometimes not. It is not uncommon to order two or more of a certain part, only to find you get mixed stock of old and new inventory. We just had it happen with replacement spouts for the 3-gallon LinQ fuel caddy. Ordered two, one was the “old” black and green parts, one was the “new” yellow parts. It happens.
