I own a 1983 Yamaha midnight maxum XJ750, it has 70,000 KMs on it. Last summer the shifter jamed and was stuck in 1st gear, you could get netural by holding the shifter up with your foot. I parked the bike for a few weeks and when I tried it again all was working fine. Any suggestions on the problem? One spark plug is also white at the end, cylinder running hot, so I guess I need to balance the carbs, need to make a YICS tool, I have a plan to make one. I am thinking of giving up on the bike as it is old and has lots of clicks on it, there appears to be a leak in the cylinder block gasket, I already replaced the cylinder head gasket. I feel very uncomfortable riding any distance as the shifter may jam again.