HI, 2002POLARIS SPXP600 WITH M-IO. WHAT GEARS WILL BE BEST FOR TOP END, WHICH WILL BE BEST FOR BOTTOM. THE GEARS I HAVE ARE 23-39 AND 24-40. ALSO WHAT IS FACTORY SETTING FOR THE NEEDLE VALVES. TOP END IS BETWEEN 85-90MPH. WHAT WOULD BE A GOOD SPRING COLOR AND WEIGHT. THANKS SO MUCH FOR YOUR HELP. PUFF

Your best top end - speed- sprockets would the 24 and 39 paired. The best combination for low end will be the 23-40 combination. I'm not sure what you're looking for but the fact that you list speed suggests that is your issue. You may be more interested in clutching info. I can't help as I only run stock clutches and change my sprockets by a tooth or two to get a more favorable low end for pulling sleds.