I put about 65 miles on the 16H last weekend and filled up on the way home after going onto reserve.
Strangely the 'edge' seemed to have gone off it after that and I had an idea that perhaps some dirt had gone into the carb.
I tried the usual trick of leaving it in the garage for a week and, as usual, it hadn't fixed itself. I took it out yesterday and it definitely felt rich and fluffy. I took the carb off for the umpteenth time, checked and blew through everything but found no obvious fault until I came to put it back together - That almost new NOS float's heavy ! It shouldn't slosh like that !
The solder joint underneath where the tube finishes was porous or partly open. It took about half an hour of shaking to get it empty. It's all soldered again now but the weight of the lead / tin underneath has probably taken off some buoyancy.
A leaky float should have been obvious if I'd diagnosed logically.
At least it's flying again today 
There have been suggestions that ethanol can attack various metals and alloys. Anyone else had float problems recently ?
Is there a maximum weight for a 276 float ? I assume that there is a reasonable margin for error ?
you just add a little fishing cork to the top. That keps em from sinking too deep!
email (option): micran1234@yahoo.com