I'm trying to adjust the transmission on this '91 RockHopper and i it's giving me issues (I'm inexperienced). The front derailleur won't go far enough up on the biggest chain ring, so the chain grinds. At the same time, if I adjust it so it stays far enough up, I can't change down to the smallest ring anymore. The cables are all new, but everything else is from the 90's. Could the age be the issue or can this be salvaged?