Hey guys for those like me with the stock clutch primary and secondary I have been playing with clutch kits trying to put the best power to the ground. I first ordered the Quadboss big tire clutch kit which I later found was designed for 27" tires which the 900S has stock. This kit worked great and helped over stock but I still needed to rev a little more and I needed a little more lowend so I ordered the QuadBoss Mudder clutch kit. The mudder clutch kit is designed and recommended for 28-29.5" tires. Both these kits are designed for stock motor. Or atleast thats what it states on the instructions that comes with.
Both clutch kits comes with a white primary springs so clutch engagement is basically the same, The difference is the weights and the secondary spring.

My setup is BMP tune, HMF exhaust, QuadBoss QBT446 30" tires, RacerTech bumpers, Pro Armor seats, full Ricochet aluminum skids, and spare tire! So not light by any means.

Big tire clutch kit
white primary spring
Black/white secondary spring
Weights are EPI 60
With this kit I was taching 7800-7850 in high so I wanted to let it rev a little more. (I want to say stock rev was about 7600RPM) With this setup and draging with a stock RZR 900 we where real close to 30mph and he actually pulled me a foot or two up to this point but by 35mph we where side x side but this is when mine really started to stretch its legs and by 65 I was a head by 2 lengths, by 70 I was way a head.

Mudder clutch kit
White Primary spring
Black/Orange secondary spring
weights are EPI 62

I am currently running
White Primary spring
Black/Orange secondary spring
weights are EPI 60
With both kits being designed for stock RZR’s I decided to leave the lighter weights in to give it a try. If needed I will change them. I have just rode this down the road and back so far so I can’t say about the reving but it does have more lowend and it feels like it starts pulling at a slower speed. Before from a dead stock it would spin but it would track strait but now when it spins it wants to slide like it is spinning faster. Before from a 30mph punch it felt real strong but now from about 15mph it feels real strong and it revs up quicker. Hopefully next weekend I will get some more time on this and do some drags with a stock bike.