Air intake structure of saddle riding vehicle

1. An air intake structure of a saddle riding vehicle,

the air intake structure being disposed in the saddle riding vehicle in which a frame including a left and right pair of main frames extending from a head tube and an air box between the left and right pair of main frames are disposed,

the frame is provided with a space that forms an intake passage between the main frames and an outer periphery of the head tube,

the intake passage including a front side intake duct that extends forward from the head tube, and a rear side intake duct that couples the air box positioned behind the head tube to a rear side of the head tube,

wherein the rear side intake duct is a separate body from the air box,

the air box has a front surface on which an opening inserted through the rear side intake duct is provided,

the rear side intake duct is coupled to an inside of the air box through the opening,

the rear side intake duct has a rear end that has a flange portion larger than the opening,

the rear side intake duct has a size so that a part from a distal end portion of the rear side intake duct to a portion right before the flange portion is inserted into the opening, the size formed to be inserted into the opening,

an internal surface of a front wall of the air box is coupled to the flange portion of the rear side intake duct inside the air box, and

the flange portion is secured with a plurality of bolts from the inside of the air box.

2. The air intake structure of a saddle riding vehicle according to claim 1 ,

wherein the head tube has a rear portion in which a tubular attachment that forms the intake passage is disposed, and the distal end portion of the rear side intake duct is coupled to the attachment.

3. The air intake structure of a saddle riding vehicle according to claim 2 ,

wherein the attachment has a radially expanding rear end portion, the distal end portion of the rear side intake duct is inserted into the attachment, an outer periphery of the distal end portion of the rear side intake duct has an attachment receiving portion that receives the rear end portion of the attachment.

4. The air intake structure of a saddle riding vehicle according to claim 1 ,

wherein the frame forms an approximately U shape in plan view with the head tube and the left and right pair of main frames, and between a U-shaped bottom portion of the frame and a front portion of the air box, a space is formed in plan view.

5. The air intake structure of a saddle riding vehicle according to claim 1 , wherein the rear side intake duct includes:

the distal end portion at a front end portion of the rear side intake duct;

an attachment receiving portion formed on an outer periphery of the distal end portion; and

a fitting groove defined between the attachment receiving portion and the distal end portion, and configured for receiving an attachment that forms the intake passage.

6. The air intake structure of a saddle riding vehicle according to claim 5 , wherein the attachment receiving portion is formed into a pipe shape around the distal end portion such that the fitting groove defined between the distal end portion and the attachment receiving portion is ring-shaped and forms a clearance configured for receiving the attachment that forms the intake passage.

7. The air intake structure of a saddle riding vehicle according to claim 6 , further comprising a seal arranged in the fitting groove, wherein the fitting groove is configured for receiving a rear edge portion of the attachment against the seal, sealing a gap between the rear side intake duct and the attachment.