Just read your column about a problem a guy was having with a secondary clutch springs that was too stiff for the sled it was installed on. It was very informative and solved a problem that I have been having with my wife’s sled (Indy 440) for the last year (i.e.. no top end). My wife is an aggressive rider but small in stature and weight. The standard 440 liquid was a great machine for her except the standard clutching which was extremely soft. What I did was take the Erlandson springs that I had from my XLT and installed in her sled. The primary was white and the secondary was yellow. As well, I used a Polaris T1 triangle helix. This setup gave a maximum rpm of @ 7900. The big disappointment was that we could only get 70 mph top end. The clutches were obviously not shifting out fully. After reading your article I pulled the Yellow Erlandson secondary out and reinstalled the stock red spring in the third hole. Just like magic the sled ran 85 mph on the speedo with me on it (@ 214 lbs) and was still climbing slowly when I ran out of room. Wow, what a difference! My question to you is this. Would I be better off installing a Polaris blue or almond/yellow primary spring? I am wondering if I am slightly above the powerband at 7900 rpm. I believe this engine should rev out at @7750. Any suggestions would be appreciated. Maybe I should leave well enough alone!!!
Perhaps the first and most important lesson you learned is that your 440 does not make as much horsepower as your XLT, and that springs that may work splendid for the XLT are going to be too stiff for the 440. If you can get that 440 to show 85 mph on the speedo with your 214 pound butt on it, leave it alone!
If you are happy with the engagement RPM of the 440, and once the sled shifts out it runs at a stable RPM then all you need to do is install slightly heavier flyweights to get the shift RPM to drop from the current 7900 RPM down to 7750. Looking at dyno numbers, the Polaris 440 is pretty flat from 7500 to 7750 RPM, so I agree that 7750 should be your target. The Polaris almond yellow is also a pretty stiff spring, and you’ll likely find that it wouldn’t allow your 440 to shift all the way out. The Polaris blue might even be a bit stiff for your 440.