First, decide if you want to go for a shim, or just upgrade with a peformance spring available at many dealers.  The shim can be made from 2&1/4 inch outside diameter exhaust pipe, or other suitable metal tubing.  Simply cut a slice out of the end of the tubing about 1/4 to 5/16 inch thick and you are good to go.  One nice thing about shimming over springs, is that you can always change the size of your shim, but with the spring kits, you will need to purchase a new spring if you want to change the characteristics... or even add a shim to the performance spring to further increase stiffness!   Oviously, if you don't have the patience or tools required to be slicing sections of exhuast pipe, you are probably better off purchasing a stiffer torque spring.  Whichever route you choose, the results will be similar.  Experimentation is key. 

The first thing you will want to do is to remove the cover from the CVT side fo the engine.  This is the long case side that appears on the left of the engine when looking at the buggy from the rear. (see picture to the right, click on picture for larger version) Since most go kart and buggy designs send the engine exhaust past this cover it will probably be necessary to first remove the muffler can (modular designs with detatchable mufflers) or the entire exhaust.  Many designs also use the splined peg from the kick start gear as an attachment method for the muffler hanger. All clamps holding onto this peg will have to be removed in order to get the cover off.  Some manufacturers have  choosen to remove the kickstart mechanism and simply send a bolt through the kickstart hole in the CVT cover as an attachement point for the exhaust canister.  For folks out there that have this type design, removing the muffler hanging hardware may not be necessary.  Once the CVT case side  is clear of obstructions, the small bolts holding the cover to the engine case and CVT arm can finally be removed.  There are many of these, and one or two may also be used to hold brackets or electrical grounds so be careful to take note of how these are attached.  Also, these bolts vary in length depending up on the part of the case they are going thorugh.  You will want to take note of which bolts go where so assembly later on will be easier.

Once the cover is off you will see a set of two large pulley units with a belt going around them. You may or may not also have kickstart gears and other related components between these large pulleys.  The rear most pully system is the driven side.  This is the unit with a large and unmistakeable clutch bell cover.  It is very different looking from the front variator side of the CVT which has cooling fins on it.