Grand Prix 250
Main Motorcycle: BSA A65 1971
Join Date: Jan 2019
Location: Taynuilt , Scotland
Other Motorcycle: Cagiva raptor 2001 650
Airbox dismount is fairly straightforward, if the carbs are out of the way and the rear of the fuel tank is raised to clear lines., unplug the zener if fitted, leave mounted to RHS. Remove outer lids and filters, the air box section bolts to two straps welded to the Oil spine with welded 5/16 UNF threaded nuts, 1/2" AF socket deals with them, for the time being leave them tight, first slacken the 1/4 unf bolts that fix the rear steel panels to the air box, then slacken the air box 5/16 bolts, if the carbs are out of the way , the steel rear panels have conveniently slotted bolt holes , they can be wiggled free from the air box, you can leave the ignition switch attached if its an early type, the steel panels can remain in situ, remove air box bolts , there should now be enough room to wiggle the air box forward then twist round to the primary side to come free.
its tempting to split the air box halves, dont, they are a pain to deal with, i find it easier to remove the carbs, better left as one unit and are painted as such usually.
You can remove the air box and side panels as one unit , but its difficult, , the motor top end gets in the way. With the top end off , its a doddle.
The air boxes are pretty castings when viewed in isolation, the die maker did a great job on these., my LHS section was cracked at the top and bent a little, it straightened after annealing and the welder made an invisible repair to the crack, your hole shouldnt be to tricky to relocate with a fresh plate in there. At a push, with no handy welder, an Al plate some panel sealer and a 1/2 dozen pop rivets would do it..
The hole in the pics looks almost like it was cut for the flat back headlight rubber bathtub ?
We have no means of establishing reality outside our own frame of reference.