The springs are between $15 & $20 and take about a half hour to change. Just a matter of taking the outer cover off the front pulley, swapping the spring, and putting it back on. Probably the best 2 places I know to get them is your Polaris dealer or Ritter Cycle. (rittercycle.com)
There are a lot of people who have done this already.
Changing the spring allows the engine to rev a little higher before the clutch grabs, letting the engine make more HP at lower ground speeds. It also runs a little higher RPM during slow-speed maneuvering.
I tried the green spring in my Xplorer, and it would wheelie in Low just by giving it more than 1/2 or 2/3 throttle from a standing start, as long as the traction was there.

 

So you would definitley recommend it?

 

If you want more power at take-off and can stand to lose a little bit of slow speed control (very little once you get used to it) I would definately say go for it. By losing a little low-speed control, what I mean is, if you like to climb out of ditches to where you have one front wheel dangling in the air, and need the absolute most control of the clutch engagement to keep from flipping it over, it might not be for you. 99% of everyone else seems to find it beneficial.
I would say either the green or white is fine, I tried both on my 99 Xplorer, and went with the white, mainly because I have some nephews from the 'city' and didn't think it wise to turn loose 14 and 15 year olds on a machine that will wheelie with half throttle without pulling up on the bars.
I had the white spring on for almost 1500 miles already (4400 miles total on my machine) and have spent less then $20 for repairs on the thing and am still on the original belt, so I would say, with the white spring, from my experince doesn't seem to have any real drawbacks. If you go with the green spring, just be sure that if you are somewhere the tires have a good 'bite' to be pointing the direction you want to go, because if you nail the throttle (especially in low) don't expect the front wheels to have much traction at first.

 

So with the white spring, could i still wheelie with a little effort, at least with less effort without it on?

 

Yes, the clutch will grab harder, making wheelies easier with the white spring. If you are familiar with your machine, don't be afraid of the green spring, either. I just shied away from it because one of my nephews believes that when in doubt, peg the throttle.
I put 2 flags up along the end of a field (didn't measure how far apart they were) and checked how fast I was going from a standing start between them. I made 2 runs each way (4 total) with each spring, and here were the resutls.
Stock spring averaged 34 MPH
White spring averaged 37.5 MPH
Green spring averaged 38 MPH

3.5 MPH might not seem like much, but keep in mind it is a full 10% increase in acceleration for under $20. The white to green had different characteristics. The green definately took off harder, but after maybe 25 MPH or so, the white seemed to pull stronger, and the white had a 2 MPH top speed advantage over the green. For pulling bigger/more aggressive tires, though, I think the green would be better.
All my results are with a 99 Xplorer 400L. Many people have tried changing springs, and it seems to help more with the 2 cycle engines than it does with the 4 cycle.

I might suggest getting both from your dealer, with the understanding you will try both, keep the one you like better, and get a refund for the other.

 

Ok, so maybe I will be fine with green? I have a winch in front so it kinda weights front down and I also have some more agressive tires, Titan 589's that weigh more then stock. So maybe I should look at booth? or just go with green.