Because it is such and integral part of the drive system of a motorcycle, we don't always think about how it works or how to fix it. You can save yourself money fixing it yourself, but what if you don't' know what the problem is? Troubleshooting any problem is a useful skill to have, and doing it on a motorcycle clutch is easier than you think.
Start at the clutch lever on the left side of the handlebar. Pull it in and see how much free play there is between the time you start pulling and when you feel resistance. If there is more than about a quarter inch of play, your clutch may not be disengaging fully when you pull it in.
Check the clutch master cylinder (if your bike has one). It looks just like the brake master cylinder on the other side. Clean the cover and remove it to see the fluid inside. The fluid (commonly DOT 3 or DOT 4 brake fluid) should be relatively clear and amber colored. If it is brown or murky, flush and bleed the system to get it clean.
If you don't have a hydraulic clutch, check the cable connections on each end of the clutch cable. Tighten and clean these connections as necessary. It is a good idea while looking at the clutch cable to lubricate the cable housing. You can find cable lube at most motorcycle repair shops or dealerships.
If your issues persist, the problem may actually be inside the clutch itself. Consult your motorcycle's shop manual to see which side of the engine case your clutch basket is. Usually the clutch basket is found on behind the right side engine cover. Removing this cover is a simple matter of draining the oil and removing the bolts around the outside.
Remove the clutch springs that are holding the clutch plates in. Check each one of these springs' length at rest. Every spring (typically, there are five) should be the same length.
The clutch itself is made up of a series of discs. The discs with the gear teeth on the outside are called pressure plates, and the discs with the gear teeth on the inside are called friction plates. These discs should alternate, should not be sticky, and should not be out of round. Anything less than perfectly round can mean a malfunctioning clutch.
