This is a notice from the board:
"Weber Carb Air Filter
The saga of the weber carb continues with the fitting of the air filter. Some drivers have found that the process of fitting the air filter to the carburettor adapter plate can cause particles of the ribs around the inside of the filter neck to break off and be sucked into the carburettor so causing bad running. Experience has shown that it is better to fit the filter to the adapter whilst it is detached from the carburettor, clean the whole assembly with an air line and then secure the combined fitting to the carburettor. Any detached particles will then be cleaned out prior to final fit to the carb. Of course there may be other ways of achieving this result. Competitors are also reminded to check the 2012 rules generally regarding the weber carburettor kit and its fitments."