platic tanks are great i use what i call the saddle bag tank . kinda like a side tank but it only works with diaphram carbs , with the medal tanks made for the gravity feed carbs , i never mount them with just a single clamp pulling the studs out of the bottom of the tank happens from this . at the least it will make them leek . what i do is use a double set of clamps around the top tube with long 6mm studs going up then i thread 6mm extension onto the tank bolts with lock nut above that now just line it up and screw the tank onto the 6mm studs coming up from your clamps . an added benifit is one less vibration to worry about . the tank doesnt rattle against the bike . you might be able to see it in this picture this tank is the extra large tank from dax.com . very nice tank . the cap fits good but doesnt come stock with extra clamps you will have to ask for that .
townie picture by thescooterguy - Photobucket