I am writing this because I don't know if this forums has a step by step on this or not...
1. The beginning - Remove drive clutch from engine, the bolt will be on the output shaft of the motor, you'll need an impact wrench or a box end wrench and another to tap the box end using blunt force to remove the bolt. Once you have the bolt out it should come right off the shaft easily aside from any rust that keeps it on the shaft. Grease the shaft slightly with no clutch on there to make removal easier in the future.
2. Disassembly - Place the clutch assembly on a work bench or table and remove the outer cover, keep notice that the hub in the assembly has the flat side down and the molded side up which will fit exactly in the cover. Remove the hub, set it aside. Remove the bronze bushing off the backplate and set that to the side. Remove the spring pack assembly if you have not checked it recently for wear, if this is hard to remove try wedging a flat blade screwdriver for ease.
3. Analysis - See if the clutch is in good shape, the main part of the drive clutch will have an aluminum spring pack assembly which has 2 springs which when removed should spring out straight when unhooked and both pins should be firmly inside the aluminum. If either of those are wrong you may need to replace something. Check the bronze bushing for a crack where it may have broken. In the main assembly and the hub, check side to side play, this should be a fairly firm fit, it should not have much room to wiggle left and right, a large amount of play will indicate the clutch is heavily worn from use and may need to be retired. As with most things, if you notice wobble in the clutches, this is sometime repairable but usually is the kiss of death.
4. Cleaning - The hub needs to be cleaned, the best tool for this is a wire wheel on a bench grinder, clean the hub of any material. Next take a wire brush and brush out the splines in the main assembly and make sure it is nice and free of debris, it may need a rat tail file the very first time you do this, we use a diamond bit chainsaw sharpener for fine cleaning. The sides of the clutches which the belt rides on need to be cleaned to where there is no rust or pitting, it needs to be smooth. Start with a wire wheel and if severely rusted you may move to a sand paper, we use a pneumatic 3M sanding wheel to clean these when in bad shape. When cleaning the hub and main assembly that hub should be able to drop clean through the assembly into the palm of your hand with no problems. If it does not do so, it is not clean enough.
5. Re-Assembly - Place the spring pack assembly back into the main portion of the drive clutch, this should be flat side down, angled side up. If you have trouble placing this back in the assembly you may need that flat blade screwdriver, we also take use of a 4x4 as wood will not damage the assembly if you need to smack it into place. Place the bronze bushing back onto the back plate, place the hub, ridged side up back into the main part of the assembly.
6. Lubrication - This is a dry assembly, no wet lubrication PERIOD. The only part that would need lubrication would be the inner side of the outer cover on the main assembly where the aluminum piece rides on it using centrifugal force. The lubrication in question suggested by Comet is their own brand of dry lube, which is a dry moly blend, I'm sure there are other fine companies out there that offer this, but it doesnt need lubrication often, its not that big of a deal, the main thing you need to focus on is cleaning the clutch. Any wet lubrication you do put in this will create a terrible snowball effect which will collect more dirt, dust, belt fiber, debris, etc. Bad idea to use wet lube.
7. Re-Installation - Put the clutch back on your kart, backplate first with the bronze bushing, then the main portion of the drive clutch beveled side first, outer plate away from the engine etc. Screw the bolt, lock washer, and flat washer back on the kart, if you have an impact wrench this is the time to use it, if not use a box end wrench and pull the recoil to lock up the washer and keep the bolt firmly in place.
The end - Comet did suggest you clean this every 5 hours of use, but if you ride in the sand or an excessively dirty area, I'd say you need to make this part of what you do following riding during the clean up and maintenance time you put into keeping your kart in good shape.