My breathers have previously been modified to VTA. Going to fit a catch can and just measured the pipework...should be 10mm ye ( classic )...ID 13mm? Can this be right? Just want to clarify before I order a " special fit " and waste my moola!

 

I assume this is the head breather yes 13 mm ID

 

Both head breathers and crank case ( 1 blanked, 1 same size pipe as head ). If this is so why is that everyone else is using 10mm?