I stopped by both of my Ski-Doo dealers to buy a replacement spring for my secondary clutch. As it turns out neither of them stock these items. I was informed that they never go bad so why change them. I have been accustomed to changing my clutch springs at the beginning of each season as a matter of principle for years. Have I been throwing my money away? I guess a guy could crank up the spring tension to compensate for a worn spring? What about the primary springs? I’ve been changing them also. The health of the primary spring can be determined by measuring the free length and comparing it to the spec – right? Help!
Lee in Spokane
This is not as easy of a subject as it may first appear. Spring fatigue and replacement should be done on a case by case basis, and there is no good rule of thumb to go by. Most springs will take a set after a few hundred miles, and then their fatigue should be pretty gradual from that point on with fairly consistent performance. As long as the clutch tuning is done after the springs take a set, then there should be no reason to replace them each season. (If you want a primary spring to take a “quick set”, compress it in a bench vise overnight.) I would replace springs in the clutching system based on performance, not as a matter of precaution.
Dependent on the quality of the wire material that the spring is made of, and how close to the “physical limits” the spring is being stressed to, you will have some springs that have a poor “memory” and do not always return to the desired tension. As for the secondary, you could measure the pre-tension (with a spring scale or fish scale) and maintain it to the same pressure and be OK. Yes, measuring the free length is a good indicator of primary spring condition, but this spring is one that will fatigue and the shift characteristics will change. Usually your operating rpm and engagement rpm will drop when the free length becomes shorter. This one will drive the unsuspecting tuner nuts. Know your free length and measure it when troubleshooting.
Suspension springs are another story. After consulting with a major shock supplier to the snowmobile industry, they informed us that whenever a shock is replaced the coil spring should be replaced also. The suspension springs are placed under extreme loads (very close to their design limits) and will exhibit fatigue and, especially with matched sets, the variation between the springs can be quite great. This was news to me, as I have never replaced a suspension spring unless it was broken or clearly shot. Since the shock supplier doesn’t sell springs to go with their shocks, I would have to tend to believe them.