I need to remove the 3 bolts holding the air intake back plate in position, I thought these were 7/16" but my sockets don't fit.
Anyone know what size! advise very much appreciated.

 

Hello old chap from elsewhere in England and welcome to HDF. You can see what your stock air cleaner is/was like on-line here. AFAIK the back-plate is a black plastic moulding, held on with three screws, not bolts, so it seems likely that you don't have a stock airbox, or someone else has replaced the screws with bolts. There are only so many bolt-head sizes and they are bound to be inch AF, so your options are few! Is your 7/16" socket too bit or too small?