I've been able to fix my flooding carbs before by really polishing up the sealing part of my float needles. Going as far as spending an hour with a box of cotton q-tips and carb cleaner to make 100% sure that those contacting surfaces will seal up. Then attaching a clean hose to the fuel inlet, flipping the assembly upside down and attempting to blow air by mouth into the carbs to be sure every bowl seals up when the floats are lifted. Mind you this would only work if your float levels are ok. At least that's what has worked for me on these carbs
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I've noticed that carbs from other bikes have rubber tips on the float needles. I wonder if those would provide a more reliable seal instead of metal-metal contact. Anyone ever make an attempt at seeing if those will fit?