After riding season is over, drain and remove your tank, take it to a local shop that can PROPERLY boil and reseal it. Again PROPERLY boil and reseal it. My R90 tank cost me about 45.00 to have this done. If not PROPERLY done the sealantused can come loose and invade the carbs. make certain you use someone with a long standing GOOD reputation. A lot of radiator shops that specialize in older ( pre 70's ) cars also offer this service.