There is no need to take anything off the engine just to adjust your clutch. It's normally adjusted at the lever end. Some might have an additional barrel that can be adjusted somewhere along it's length. On some bikes the internal pushrod can be adjusted, but I believe it's more common to street rather than dirt bikes. The cable for your bike is $21.18 from BikeBandit. If adjusting the cable doesn't cure your problem, then you will need to pull the clutch cover and inspect your clutch to find out what's wrong.
Marc -