4. Air box installation amendments When running through the existing air box and filter a small modification is required to make the induction process more effective.
Series 1 & 2
We would suggest that the air scoop under the seat is removed completely. If you have separate seat we advise finding a spare scoop and removing the lower portion of the intake area to improve the volume of airflow. Alternatively, if you have a series two air box with a “strangle neck” type pipe to the air scoop. We would recommend finding a TV type box with a wider neck or sacrificing a “strangle neck” air box by drilling a series of 12mm holes in a honey comb pattern on one side of the box. These holes are then reasonably well hidden by the fuel tank or glove box. The top inlet pipe of a “strangle neck” air box has a diameter between 19-24mm, this is a great restriction on the induction process and must be changed if improvements in performance are required.
For the purest look the scoop can be left but it will require the internal web to be completely removed. If the scoop is hidden under a single seat we would suggest removing the scoop completely. This is to prevent destruction of a perfectly good scoop. Alternatively a sacrificial air box can be used such as the description above. Once drilled as described the inlet will draw most of its air supply through the drilled holes and not the air scoop. Remember if running through an air box the main jetting will usually have to be reduced. It is therefore important that the air hose is well connected with jubilee clips. If the integrity of the air hose is compromised then the mixture will become weak. This may result in piston damage, and other associated problems.