If I remember correctly, the symmetric was tricky to set the front derailler. The right ( rear derailler ) shift lever was attached to a cam that moved the left ( front derailler ) lever shaft forewards or backwards a bit. This made tiny movements of the front derailer. This kept the front derailer from hitting the chain ring when shifting the rear derailler. The left ( front ) was a friction lever and the right (rear ) was fixed to a shaft that moved the cam. If it is the top mount style remove it from the bike using the one mounting bolt. Use a light grease to the cam. Push both levers forwards (I think ) and adjust the front cable tension to set the extra motion of the front derailler. Also note suntour front deraillers move the opposite direction to shimano when you move the left ( front ) lever.