Was doing some cleaning on my motor before tonights race. I run a mikuni on my vanny 30 cube. I removed the carb for cleaning and found that the gas has been eating away at the rubber boot. It didn't put a hole in it, but made the rubber very soft like silicone. You can actually scrape it off with your finger nail. My guess is that it will only be a matter of time before it eats it away comletely. My only guess of what is causing this is the 10% ethanol crap gas we have around here in Northern New York.