Abstract:
A motorcycle includes a muffler defining an air scoop for directing air toward the motorcycle&#39;s engine and transmission assembly. The muffler also has a substantially planar upper portion and a lower portion having a convex surface.

Description:
FIELD OF THE INVENTION 
     The invention relates to motorcycle mufflers. 
     BACKGROUND 
     Prior art motorcycle mufflers often have a substantially circular cross section. The mufflers are usually mounted near the end of each exhaust pipe. Some motorcycle mufflers are mounted near the bottom of the motorcycle frame, beneath the engine and transmission assembly. It is known to provide a fairing or air scoop that is separate from the muffler in front of the muffler to direct a flow of air up toward the engine and transmission assembly. 
     SUMMARY 
     Motorcycle mufflers often become very hot during use. Heat radiating from a muffler can cause the engine and transmission housings to heat up. This may result in a variety of undesirable effects, including rider discomfort and accelerated wear of engine components. 
     The present invention provides a motorcycle having a frame, an engine and transmission assembly interconnected with the frame, and a muffler interconnected with and in communication with the engine&#39;s exhaust manifold. The muffler includes a front portion defining an air scoop sized and shaped to direct cooling air between the muffler and the engine and transmission assembly. The air scoop may also be used to direct cooling air toward the engine and transmission assembly while the motorcycle is moving. The invention also provides a motorcycle having a muffler that has a substantially planar top portion, and a lower portion including an outer surface defining a convex curve. 
     Because the muffler of the present invention directs air toward the engine and transmission assembly, there is no need for an additional fairing that is separate from and mounted in front of the muffler. Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a right side elevational view of a motorcycle embodying the present invention. 
     FIG. 2 is a left side elevational view the motorcycle muffler illustrated in FIG.  1 . 
     FIG. 3 is a top plan view of the motorcycle muffler of FIG.  2 . 
     FIG. 4 is a cross section view taken along line  4 — 4  in FIG.  3 . 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify steps of a method or process is simply for identification and is not meant to indicate that the steps should be performed in a particular order. 
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a motorcycle  10  including a frame  14 , front and rear wheels  18 ,  22  mounted for rotation with respect to the frame  14 , a steering assembly  26  for the front wheel  18 , a gas tank  30 , and a seat  34 . An engine and transmission assembly is mounted to the frame  14 . The engine and transmission assembly includes an engine  38  and a transmission  42 . The engine  38  drives an output shaft of the transmission  42 , which in turn drives the rear wheel  22  through a drive member  46 , such as a belt or chain. The illustrated engine  38  is a single-cylinder engine, but the invention may be embodied in a motorcycle having a multiple-cylinder engine. The engine  38  includes a combustion chamber  50  and an exhaust manifold  54 . 
     An exhaust pipe  58  communicates between the exhaust manifold  54  and a muffler  62  mounted below the engine and transmission assembly to carry products of combustion from the combustion chamber  50  to the muffler  62 . The illustrated muffler  62  is mounted below the engine and transmission assembly, but may alternatively be mounted substantially anywhere on the motorcycle  10 . For example, in a motorcycle having a two-cylinder engine, one muffler  62  may be provided for each of the exhaust pipes  58  associated with the two cylinders, and the mufflers may be positioned on each side of the motorcycle  10 . A gap  64  is defined between the engine and transmission assembly and the muffler  62 . 
     FIGS. 2-4 better illustrate the muffler  62 . As seen in FIG. 4, the muffler  62  includes an inner wall  66  and an outer wall  70 . The muffler  62  includes a substantially planar upper portion  74 , a convex lower portion  78 , and side portions  80  joining the upper portion and lower portion  78 . The outer wall  70  has a radius of curvature  82  of about 8.5 inches in the lower portion  78 , and has a width  84  of about 5.5 inches. The width  84  of the lower portion  78  is less than about 75% the width  90  of the upper portion  74 . Preferably, the width  84  of the lower portion  78  is about 56% the width  90  of the upper portion  74 . 
     The muffler  62  has a length  86  of about 27 inches, a width  90  of about 10.75 inches, and a height  94  of about 3.75 inches. The width to height ratio is preferably at least 2:1, and more preferably at least 2.75:1. Cut-outs  98  are provided to accommodate various pipes and other motorcycle components near the muffler  62 . As seen in FIG. 2, indentations  102  are provided on either side of the muffler  62  to accommodate a mounting strap  106  (FIG.  1 ), and a mounting bracket  110  is also provided for mounting the muffler  62  to the rest of the motorcycle  10 . 
     The muffler  62  also includes a front portion that defines an air scoop  114 . As seen in FIG. 1, the air scoop  114  directs air toward the engine and transmission assembly when the motorcycle  10  is operating and moving in a direction of travel  116 . Some of the air, identified by reference numeral  118 , is directed up toward the front of the engine and transmission assembly. Some of the air, identified with reference numeral  120 , is directed through the gap  64  between the muffler  62  and engine and transmission assembly. 
     The air scoop  114  defines an angle α (FIG. 2) of between about 110° and about 160° with respect to the direction of travel  116 , and has a radius of curvature  122  between about 7 inches and about 11 inches. Preferably, the angle α is about 125°, and the radius of curvature  122  is about 9 inches. Alternatively, the muffler  62  may be mounted above or to the side of the engine and transmission assembly, provided the air scoop  114  directs air toward the assembly. The air scoop  114  is formed by curvature of the outer wall  70 . The air scoop  114  widens from about 4.25 inches at its lower end to about 9.75 inches at its upper end. The air scoop  114  preferably extends forwardly of the exhaust pipe and muffler junction a distance  126  of about 1.5 inches.