Here's the Air Box modification for the 99 Ninja 250, I posted on some other forums:
Found it difficult to remove the carburetor with the stock air box, thought it would probably be difficult going back together, too.
Decided to go with the K & N "drop-in" KA-2586 air filter keeping the original air box. Still wanted to modify the air box making it easy to remove/install the carburetor.
Removed the air box original brackets & foam filter as per K & N instructions.
This can be skipped if the original foam brackets and foam element
are to be used.
Removing air box split in half with one side slid forward & one side slid back with carburetor removed. Had to be "patient" getting the two air box halves out to be cut.
Air box halves before modification.
When cuts were made with the hacksaw, had to be "sure" the battery box was cut off without making any cuts or holes in the air box!!!!!!!
Air Box halves with battery box halves.
Snorkle modification for the K & N filter. This can be skipped if the original foam brackets and foam element are to be used.
Battery box bolted together.
Lots of room between the carburetor and air box with the battery box removed and air box slid back.
Air box installed with original battery box bolted in.
Hose Clamps installed on the air box hose to carburetor.