Usa models are equipped with an additional system with an evaporative emissions canister that prevents fuel fumes from being discharged into the atmosphere.
The breather hose (4) is connected to the canister filter (1); when the fuel has been filtered, it is returned through the hose (2) to the horizontal (a) and vertical (b) intake manifolds via the hoses (2a) and (2b). Drainage pipe (c) and the hose (5) vent to the ground.
For correct positioning of the connection hoses consult the indications given below.

Evaporative emissions canister
Removal of the evaporative emissions canisterTips on how to select the sensitivity level
Warning
The 8 level settings of the dtc were calibrated using tyres of the
same make, model and size as those originally fitted to
the motorcycle.
The use of tyres of different size to the original tyres may alter the operating
characteristics of the system.
In the case of minor differen ...
Refitting the air filters
Apply universal sealant in the air duct (2) and (6) groove (d).
Fit seal (7) in the groove (d) having care to place it correctly in the relevant
seat so as to avoid abnormal wrinkles.
Pull out the filter cartridge (1) from the seat in the airbox.
Position the rh air duct (2).
Start ...
Overhaul of the crankcase halves
Carefully examine the engine crankcase halves.
Check that the surfaces of the crankcase halves are perfectly flat using a
reference surface.
Check that the bearings (1) and (18), and the bushings (2) and (17) are in
optimum conditions. Note that the main
bearings must always be changed in p ...