Oil tank cap

1. A motorcycle comprising:

a frame;

a front wheel coupled to the frame;

a rear wheel coupled to the frame;

an engine supported by the frame and adapted to propel the motorcycle;

an oil tank supported by the frame and including an inlet defining an inlet aperture having an inlet axis; and

an oil tank cap rotatable about the inlet axis between an inserted position and a sealed position, the oil tank cap having a movable portion movable substantially along the inlet axis between a retracted position and an extended position, wherein the outer surface of the movable portion is not planar.

2. The motorcycle of claim 4 , wherein the movable portion includes an outer surface and the oil tank includes an outer surface, and the outer surface of the oil tank cap is flush with the outer surface of the oil tank when the oil tank cap is in the sealed position and the movable portion is in the retracted position.

3. The motorcycle of claim 2 , wherein the oil tank includes a cover member and the outer surface is an outer surface of the cover member.

4. The motorcycle of claim 1 , wherein the outer surface of the movable portion is not symmetrical about the inlet axis.

5. The motorcycle of claim 1 , wherein the oil tank includes a protrusion and the oil tank cap includes a recess sized to receive the protrusion, the recess located such that the oil tank cap is oriented in a first orientation when in the inserted position.

6. The motorcycle of claim 5 , wherein the recess includes a groove, and the protrusion moves along the groove during rotation of the oil tank cap between the inserted position and the sealed position.

7. The motorcycle of claim 1 , wherein the oil tank includes a first protrusion and a second protrusion and the oil tank cap includes a first recess and a second recess and wherein the first recess is sized to receive only the first protrusion.

8. The motorcycle of claim 7 , wherein the first recess includes a first helical groove and the second recess includes a second helical groove.

9. An oil tank cap for an oil tank having an inlet defining an inlet aperture and an inlet axis, the cap comprising:

a first portion adapted to be inserted into the inlet, the first portion rotatable about the inlet axis between an inserted position and a sealed position; and

a second portion mounted to the first portion and movable parallel to the inlet axis relative to the first portion between a retracted position and an extended position, wherein the orientation of the second portion is substantially fixed relative to the first portion.

10. The oil tank cap of claim 9 , wherein the second portion includes an outer surface and the oil tank includes an outer surface, the outer surface of the second portion adapted to be flush with the outer surface of the oil tank when the first portion is in the sealed position and the second portion is in the retracted position.

11. The oil tank cap of claim 10 , wherein the oil tank includes a cover member and the outer surface of the oil tank is an outer surface of the cover member.

12. The oil tank cap of claim 9 , wherein the first portion includes a recess sized to receive an oil tank protrusion, the recess located such that the first and second portions are oriented in a first orientation when in the inserted position.

13. The oil tank cap of claim 12 , wherein the recess includes a groove, and the protrusion moves along the groove during rotation of the first and second portions between the inserted position and the sealed position.

14. The oil tank cap of claim 9 , wherein the oil tank includes a first protrusion and a second protrusion and the first portion includes a first recess and a second recess and wherein the first recess is sized to receive only the first protrusion.

15. The oil tank cap of claim 14 , wherein the first recess includes a first helical groove and the second recess includes a second helical groove.

16. The oil tank cap of claim 9 , wherein the first portion includes a first recess and a second recess wider than the first recess.

17. An oil tank cap for an oil tank having an inlet defining an inlet aperture and an inlet axis, the cap comprising:

a first portion adapted to be inserted into the inlet, the first portion rotatable about the inlet axis between an inserted position and a sealed position; and

a second portion mounted to the first portion and parallel to the inlet axis relative to the first portion between a retracted position and an extended position, wherein the second portion includes an outer surface and the oil tank includes an outer surface, the outer surface of the second portion adapted to be flush with the outer surface of the oil tank when the first portion is in the sealed position and the second portion is in the retracted position, and wherein the outer surface of the second portion is not planar.

18. The oil tank cap of claim 17 , wherein the outer surface of the second portion is not symmetrical about the inlet axis when the first portion is engaged with the inlet.

19. A method of assembling an oil tank having an inlet defining an inlet aperture and an inlet axis, the method comprising:

engaging an oil tank cap with the inlet;

rotating the oil tank cap about the inlet axis from an inserted position to a sealed position;

moving a movable portion of the oil tank cap from an extended position to a retracted position;

maintaining the movable portion of the oil tank cap in the retracted position; and

matching the contour of the outer surface of the oil tank cap with the contour of the outer surface of the oil tank when the oil tank cap is in the retracted and sealed positions, wherein moving the movable portion includes moving the movable portion such that an outer surface of the oil tank cap is substantially flush with an outer surface of the oil tank.

20. The method of claim 19 , wherein moving a movable portion includes pressing and releasing the movable portion.