i dont understand how you could possibly have a 5000rpm engagement, as the w/w/w/ spring is 45/119kg, the spring you have in now is 40/114kg, its only 5kg differnt it might be about 300-400rpm differnt, so it will engage at 4000rpm instead of 35-3600rpm likely, but you cant get to 5000rpm with that spring unless you use a 8-10mm shim in the clutch cover(making the spring stronger because your shimming it shorter). Yamaha doesnt make a spring with more then 45kg. start. All those spring will engage right around 4000rpm. To get a 5000rpm engagement speed youd need a 55-60kg start. The less start kg the lower the engagement speed will be. Weights, and rivet placement do have a little bit of impact on engagement speed, but you cant change it a 1000rpm unless you use thick shims or go to a stronger spring start.
you do have a long spring primary clutch cover on it... right?
the reason i suggested the w/w/w/ is that its only 5kg more on the shift which will raise the shift rpm some and will backshift it slightly better. if you want more backshift it would be better to drill a hole thru the tip rivet and lighten it up a tad, go back to 4 grams. i have ran redhead engines at 8300-8500rpm and they run great anywhere in that range with the stock pipe.
its certainly acceptable and done all the time to tune the back clutch to the snow/riding conditions, usually 60-70 twist is general snow riding, if its wet and heavy snow youll need more twist like 80-90, if its glare ice you ride on and want topspeed you go lower on twist. The rear clutch is the torq. converter, it controls the shift. I like to use a spring thats soft enough to do everything I do with the sled, a red is soft, green is stiffer then red, the silver is really stiff and unless you have a roller sec., its too stiff for good snow performance, great on grass racing. I fyou find yourself having your sec spring up at 80-90 all the time like with ared for example alot of times youll find bumping up to a green at a lower twist will work better overall, as once your past 90 twist the rear clutch becomes a heat maker and will ruin your shift cirve because it wants to backshift while the front is upshifting.
If you ride like that video alot, you would really like a roller secondary clutch on that sled as it will make it more revy and very quick backshift , with a long track your not worried about top speed anyways, a roller secondary clutch would be a great improvement for you. See if hauck still makes them they go on your stock clutch and still uses the stock yamaha helix style, all youd need is that and a silver sec spring.
