you do not need to take in. most likely is the chain tensioner. A bolt sticking out the nose side of the chain case, it also has a lock nut on it. You tighten it up by hand then use a wrench to tighten lock nut. Problem fixed.
They only other thing would be the linkage on top of the chain case, but it doesnt sound like it. But in case it is, just turn the thumb wheel on the linkage until it shifts propperly and then tighten the lock nuts.