My 2000 F4 has 16K miles on it. Sometimes when I shift up or down it seems to skip and not go into gear properly and has the sound like the chain is just spinning freely on the sprocket but I have to tap again and it will go into gear. This happens when upshifting and also downshifting but not every time. Maybe every 20 or 30th time I shift. Someone said this could mean the clutch needs adjustment or the chain is old, but the chain is in OK condition. What do you guys think?