FIELD OF INVENTION:
This invention relates to an internal combustion engine having an engine starting system and, in particular, to the means by which the engine starting system is mounted to the engine.
An internal combustion engine, used as a prime mover in two or three wheeled vehicles, is typically provided with either a kick start or an electric start. The starting system employed in such vehicles is normally of two configurations -either the starting system operates through a one way clutch or a system, commonly known as a 'bendix' drive, in which the starter gear is permanently engaged with the crankshaft of the engine. In the former case, the starter motor shaft drives the counter gear, mounted freely on the counter shaft driving the starter gear mounted on the starter guide. The starter gear transfers the motion to the magneto through a one way clutch. The magneto fastened to the crankshaft drives the crankshaft during cranking of the engine. Once the engine has attained a predetermined speed, the one way clutch disengages from the starter gear.
In engines which employ the one way clutch mechanism in the starting system, such as those used in motorcycles suitable for everyday purposes, the starter gear is mounted between magneto and crankcase. This results in increased length of crankshaft to accommodate the starter gear. Moreover, the increase In length of crankshaft leads to other performance issues such as increased weight, increased cost and possibility of crankshaft whirling, among other disadvantages. This may, in turn, lead to issues with the durability of the starting system and the engine.
It is an object of the present invention to provide an engine with a starting system mounted to the engine to address disadvantages of the kind described above.
With this object in view, the present invention provides an internal combustion engine comprising:
an engine starting system comprising a starter gear;
a crankshaft having a first section and a second section; and

a magneto assembly mounted on the first section of the crankshaft and having a mounting portion for the starter gear of the engine starting system wherein the starter gear is directly mounted on the mounting portion outboard of the engine.
A surface, such as the inner diameter, of the starter gear advantageously bears against a surface of the mounting portion. This simple plain bearing, or bush, is a wet bearing supplied with lubricant from a hydrodynamic lubrication system with advantage in terms of durability. A simple construction such as this also allows the dimensions of the starter gear/mounting portion assembly to be reduced and this may provide a packaging benefit.
The starting system may operate through a clutch, such as a one way clutch, in which the starter gear transfers motion to the magneto through the clutch.
The mounting portion of the magneto assembly is provided for mounting of the starter gear though it may possibly serve other purposes. In one embodiment, the starter gear is mounted on an extended surface of the magneto cover, this extended surface forming the mounting portion. This extended surface may be located on a side of the engine opposite to and away from the centerline of the engine.
The extended surface of the magneto cover may be provided with a surface for mounting the starter gear eliminating the need for various additional components such as guide bush, fastening of bush on magneto cover and so on. This would additionally save on machining and assembly operations positively impacting on engine fabrication cost. This surface may take the form of a boss or protrusion which may be cast over the magneto cover during engine manufacture. Preferably, the starter gear is mounted on the boss of the magneto cover.
Such mounting of the starter gear, away from the crankshaft, but in co¬operation with an element - the magneto - which rotates in synchrony with the crankshaft has benefits over direct mounting on the crankshaft. In particular, there results a shorter length of the crank shaft, the length being reduced by the width of the starter gear and associated guide bush assembly, the space required for mounting a starter gear in a conventional engine. Accordingly, disadvantages

arising from previous constructions in which crankshaft length was greater may be addressed.
DESCRIPTION OF PREFERRED EMBODIMENT:
The engine including a starting system mounted in accordance with a preferred non-limiting embodiment of the invention is now explained in detail with reference to the following figures.
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Figure 1 illustrates a lay out of an internal combustion engine including a starting system according to the prior art; and
Figure 2 illustrates a lay out of an internal combustion engine including a starting system according to the preferred embodiment of the present invention.
According to Figure 1, there is shown an engine (A) with a starting system mounted in accordance with the prior art. This starting system is operated by a starter motor (1), mounted on engine crankcase (13) and is provided with a starter motor shaft (2) that in turn meshes with counter gear (3). The counter gear {3} mounted on counter shaft (4) meshes with starter gear (5). The starter gear (5) is mounted on starter guide (8) through needle roller bearing (7). The starter guide (8) is fixed on crankcase (13). Starter gear (5) is connected to a magneto rotor (11) through a one way starter clutch assembly (6) which drives the crankshaft (9) only during starting of engine. The starter gear (5) disengages once the engine attains a predetermined speed. The stator of the engine is marked as (10). The starting operation is well known to the person skilled in the art and hence does not need any further detailed explanation.
It may be observed that the starter gear (5) is mounted on the crankshaft
through a complex bearing arrangement comprising guide and needle roller bearings
and between the magneto and the crankcase. The length of the crankshaft is
therefore increased to accommodate these parts. Such increased crankcase length
leads to engine performance issues such as increased weight, increased cost and
the possibility of crankshaft Whirling, a problem caused by crankshaft imbalance, and
ii which may lead to fatigue failure of crankshaft (108).

Figure 2 illustrates an alternate engine layout in which the starting system is mounted so as to address the above noted disadvantages with the prior art layout described in relation to Figure 1. In Figure 2, engine (A1) has a starter motor (101), mounted on crankcase (112), with a motor shaft (102) that meshes with starter motor gear (103) fitted on to the drive shaft (105). The starter gear pinion (104) fixed on the other end of drive shaft (105) meshes with starter gear (106). Engine crankshaft (108) has a first section (108a) and a second section (108b).
A magneto rotor (110)!is mounted on the first section (108a) of the crankshaft (108). The starter gear (106) is connected to the magneto rotor (110) through a starter clutch assembly (107f that drives the crankshaft (108) only during the starting of the engine (A1). The starter gear (106) disengages once the engine attains a predetermined speed. The stator of the engine is marked as (111).
The magneto cover (109) of the engine (A1) is provided with an extended surface on its inner face. A second surface to this extended surface is in the form of

a boss (114) machined to create a mounting surface for the starter gear (106). Boss (114) may also be cast over the magneto cover (109) during engine (A1) manufacture with advantage in terms of reduced manufacturing time. It may be noted that the starter gear (106) is mounted to this boss (114) outboard of the engine (A1).
The inner diameter of the starter gear (106) bears directly against the boss (114), forming a plain bearing which is a wet bearing supplied with lubncant from a hydrodynamic lubrication system. The plain bearing is a simple bearing which may be contrasted with the complex needle roller bearing arrangement described with reference to Figure 1 and which allows reduction of engine production and operating cost while achieving enhanced engine durability.
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Mounting of the starter gear (106) to this boss (114) results in reduced crankshaft length and load on the crankshaft addressing weight and crankshaft whirling problems mentioned above.

With reference to the above description, it can be observed that the Applicant has provided a simple arrangement for mounting of the starter,gear which requires a shorter crankshaft, minimizes manufacturing and assembly operations, reduces engine weight and eliminates fuse of costly components like needle bearings.
Modifications and variations to the engine and starter mechanism of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present invention.

WE CLAIM:
1. An internal combustion engine comprising:
an engine starting system comprising a starter gear;
a crankshaft having a first section and a second section; and
a magneto assembly mounted on the first section of the crankshaft and
having a mounting portion for the starter gear of the engine starting system wherein .
the starter gear is directly mounted on said mounting portion outboard of the engine.
2. The engine of claim 1 wherein a surface of the starter gear bears against a surface of the mounting portion.
3. The engine of claim 2 wherein the surface of the starter gear is an inner diameter of the starter gear.
4. The engine of claim 2 or 3 wherein the bearing is a wet bearing supplied with lubricant from a hydrodynamic lubrication system.
5. The engine of any one of the preceding claims wherein the starting system is operated through a clutch, preferably a one way clutch, in which the starting system transfers motion to the magneto through the clutch.
6. The engine of any one of the preceding claims wherein the mounting portion is an extended surface of a cover for the magneto.
7. The engine of claim 6 wherein the extended surface is located on a side of the engine opposite to and away from a centerline of the engine.
8. The engine of claim 6 or 7 wherein the extended surface of the cover of the magneto is provided with a second surface for mounting the starter gear.
9. The engine of claim 8 wherein the second surface is a boss or protrusion.

10. The engine of claim 9 wherein the boss or protrusion Is cast over the magneto cover during engine manufacture.