I recently purchased a 1982 Honda ATC 200 that has been sitting in a barn for about 15 years. After cleaning the tank and carb it fired right up and it runs great. The problem I noticed is when riding it will not shift into fourth gear. It will shift in/out of N,1,2,3 just fine but when I try to go into fourth it wont grab the gear. I adjusted the clutch to the proper setting but it still wont shift into fourth. What is the best way to go about this to identify what the problem may be.