ok, my yz400f has been running a bit poor when you nail the gas from nil to WOT. as part of my winter tear down i decided to investigate. everything in the carb checked out as perfect except for this.. that's not cool! how'd this happen? there are no leaks anywhere. i clean my filter after every ride. i believe i'm currently using bel ray (maybe maxima , i can't remember right now and don't feel like walking downstairs) filter oil, but it doesn't feel as tacky as the twin air stuff i used to use. the twin air stuff could actually be substituted for glue in a pinch. i cleaned everything up and the diaphragm and all associated rubber appears to be ok. i know for a fact no sand is getting into my tank while fueling. the diaphragm is intact and isn't rotten yet. this is also the only place i could find sand in the carb. everything else was immaculately clean inside as i took it apart. anyone seen anything like this before? i want to know if there's anything i should be fixing before i put the carb back together.