Is that a 2 stage helix? Go to a progressive cut helix something that starts at 50 or 52 and ends around 38 or 36.
Another option is find a AC roller secondary with a light green spring #2 hole with a 55/53 helix then run heelclicker clutch weights,V force reeds also gear down 2 teeth on the top sprocket and a aftermarket exhaust can (lighter weight),boost bottle to clean up throttle response and jet it down a bit.
Just a few things to do.
Boost bottle companies claim hp gains with them but this just comes from how it cleans up the off idle throttle response so you will not see any gain in top end also I made a ram air kit for the genII chassis that also gave me more power but it would run it a bit on the lean side since the ventury effect that I built in to effectivly made the in coming air colder then the outside air,worked great for drags as I did not have to jet down so much on the mains but not recomended for trail as you would pull in tomuch snow dust and freeze the carbs if you were not running iso.
As with all aftermarket companies they do inflate hp no. a little but yes they do give you more hp on the 700 but not as much on smaller sleds. But the trick is to get more hp to the ground since you loose 25 to 30% of you hp through the clutches chain case and track you will gain more by making these areas more efficeint through clutching gearing etc,so it does not do anygood to add power to the motor unless the rest is up to the task.I suggest you spend so time on the chassis making sure everything is true and square and all bearings have no bind or drag in them,this includes jackshaft,driveshaft,is the suspension perfectly square ie rails etc and is it perfectly square in the tunnel is the track perfectly aligned and the skis aligned to the track (use a long straight edge run it along the track to the front of the sled and measure ski alignment to the straight edge and not the other ski) All things that I mentioned are cheap but they take wrench time and the performance increase is more satisfieing since you did it your self also you will learn more about your machine in the process.
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