How do you adjust the clutch. Mine doesn't completely disengage when I shift gears. Too much play in the clutch handle.

You need to adjust the clutch cable adjustment for the clutch handle, THEN adjust the clutch itself.

1.First go to the clutch cable. Halfway down the cable is a rubber boot. Pull the rubber boot up the cable, (Or down. Pull it. Do NOT push), until it clears the adjustment. (The adjustment is a hex shaped piece, that is made of two parts. It's called a Barrel)
Use a 9/16 inch open end wrench, and a 1/2 inch open end wrench. Loosen the lock nut until you have around 1/16th to 1/8th of an inch clearance, of slack in the handle.
(Where the clutch lever, touches the clutch lever mount on the handlebars)

2.Now open the derby cover.
(The round cover on the back of your primary cover. Not to insult your intelligence. This -> https://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=02649&store=&catId=&productId=p02649&leafCatId=&mmyId=
<-shows a custom primary inner, and outer cover. The derby cover is the round cover all the way to the right, on this custom primary cover. You can click on the photo to enlarge)

You will then see a single threaded stud, (Adjuster screw), in the middle of the clutch pressure plate.
This adjuster screw has a nut on it, to lock the screw from turning. (Jam nut)
Hold the stud end,(adjuster screw). from turning with a large flat tip screwdriver,
(May have changed to a small square end, that you use an open end wrench on), loosen the jam nut with an open end wrench.

Turn the adjuster screw in, until there is 1/8th inch slack of the clutch lever, to the clutch lever mount.
(The clutch lever mount is the part that attaches to the handlebars. The clutch lever is the part you squeeze in with your hand. The slack is the small space in-between the clutch lever, where it touches the clutch lever mount)

Now turn the adjuster screw out 1/2 turn. Tighten the jam nut. (Make sure you hold the adjuster screw in that place you set, as you tighten the jam nut. DON'T let the adjuster screw turn as you tighten the jam nut!)

3.Now tighten the lock nut, (Jam nut), on the adjustment barrel for the clutch cable. You should grease the threads of this adjustment barrel to prevent corrosion in the future. Pull the rubber boot back into place.

4.Replace the derby cover gasket as these will leak like a sieve. Replacing this gasket is cheap insurance. Install the derby cover, tighten the derby cover screws evenly. (Go to one screw, tighten until it touches. Then go to another screw, and do the same. After all three are touching, snug them down one turn at a time, going from screw to screw)

This is a thin cover. If you don't tighten the screws evenly, you can cause this thin cover to warp, and be the cause of a constant annoying oil drip.