Timing belt pulley mounting and geometry for use in internal combustion engines

1. A drive system for an internal combustion engine comprising:

a crankshaft rotatable about a center longitudinal axis, the crankshaft comprising a shaft portion and a pin assembly configured for connection to a reciprocating piston, the pin assembly comprising a slot formed on an exterior surface thereof;

a timing belt pulley positioned about the shaft portion against the pin assembly and comprising a key extending towards the pin assembly and configured for engaging the slot such that the timing belt pulley is coupled to the crankshaft for rotation about the center longitudinal axis; and

a counterweight connected to the shaft portion;

wherein the slot is formed on an exterior surface of the counterweight that faces the timing belt pulley.

2. The drive system of claim 1 , wherein the pin assembly comprises:

a crank pin connected to the shaft portion substantially opposing the counterweight and spaced radially from the center longitudinal axis.

3. The drive system of claim 1 , wherein the timing belt pulley comprises a nylon resin material.

4. The drive system of claim 1 , wherein the timing belt pulley is coupled to a camshaft assembly associated with the reciprocating piston.

5. The drive system of claim 4 , comprising a timing belt coupling the timing belt pulley to the camshaft assembly.

6. The drive system of claim 1 , wherein the timing belt pulley comprises:

a first gear configured for driving a timing belt connected to an overhead camshaft assembly; and

a second gear configured for coupling with a governor system.

7. The drive system of claim 6 , wherein the first gear has a first diameter and the second gear has a second diameter that is different than the first diameter.

8. The drive system of claim 7 , wherein the first diameter is smaller than the second diameter.

9. The drive system of claim 1 , wherein the slot formed on the exterior surface of the pin assembly has an elongate shape that extends a radial distance with respect to the center longitudinal axis that is longer than a length of the key; and

wherein the key is substantially angularly constrained but is moveable in a radial direction with respect to the center longitudinal axis within the slot.

10. A drive system for an internal combustion engine comprising:

a crankshaft rotatable about a center longitudinal axis, the crankshaft comprising:

a shaft portion;

a crank pin connected to the shaft portion and spaced radially from the center longitudinal axis and configured for connection to a reciprocating piston; and

a counterweight connected to the shaft portion substantially opposing the crank pin, the counterweight comprising a slot formed on an exterior surface thereof; and

a timing belt pulley mounted about the shaft portion for rotation about the center longitudinal axis, the timing belt pulley comprising a key extending towards the counterweight and configured for engaging the slot.

11. The drive system of claim 10 , wherein the timing belt pulley comprises a nylon resin material.

12. The drive system of claim 10 , wherein the timing belt pulley is coupled to a camshaft assembly associated with the reciprocating piston.

13. The drive system of claim 12 , comprising a timing belt coupling the timing belt pulley to the camshaft assembly.

14. The drive system of claim 10 , wherein the timing belt pulley comprises:

a first gear configured for driving a timing belt connected to an overhead camshaft assembly; and

a second gear configured for coupling with a governor system.

15. The drive system of claim 10 , wherein the slot formed on the exterior surface of the counterweight has an elongate shape that extends a radial distance with respect to the center longitudinal axis that is longer than a length of the key; and

wherein the key is substantially angularly constrained but is moveable in a radial direction with respect to the center longitudinal axis within the slot.

16. A method for mounting a timing belt pulley on a crankshaft of an internal combustion engine, the crankshaft comprising a shaft portion, a counterweight connected to the shaft portion, and a pin assembly configured for connection to a reciprocating piston, the method comprising:

positioning a timing belt pulley about the shaft portion against the pin assembly;

aligning a slot formed on an exterior surface of the pin assembly with a key extending from the timing belt pulley towards the pin assembly; and

engaging the key on the timing belt pulley with the slot in the pin assembly such that the timing belt pulley is coupled to the crankshaft for rotation about the center longitudinal axis;

wherein the slot is formed on an exterior surface of the counterweight that faces the timing belt pulley.

17. The method of claim 16 , wherein the pin assembly comprises a crank pin connected to the shaft portion substantially opposing the counterweight and spaced radially from the center longitudinal axis.

18. The method of claim 16 , comprising coupling the timing belt pulley to a camshaft assembly associated with the reciprocating piston.

19. The method of claim 18 , wherein coupling the timing belt pulley to a camshaft assembly associated with the reciprocating piston comprises coupling a timing belt between the timing belt pulley to the camshaft assembly.

20. The method of claim 16 , comprising:

coupling a first gear on the timing belt pulley to an overhead camshaft assembly associated with the reciprocating piston; and

coupling a second gear on the timing belt pulley to a governor system.