the front sprocket is held on with a c-clip and is a little difficult to access because it's in-line with the swing-arm. Just get a cheap pair of 90 degree c-clip pliers.

 

I stripped out my stock front sprocket a little over a year ago. I was told by severeal people to get the sidewinder sprockets. Very friendly on the phone. He asked me what I had. Told him Scrambler 500 4x4. He sent me out a sprocket next day ( Cali to Indy). I cant remember the exact price. I think it was around $35. I haven't had a problem out of it. I ride in lots of mud and water. Highly recommend a chain tensioner. Probably the best thing I have done for the rear drivetrain. I havent had to tighten my chain since I installed it.
Chad
Indy, IN