Abstract:
Various embodiments include a gaseous fueled engine and fuel tank assemblies, in particular the location and attitudes of the fuel tanks. One or more fuel tanks are attached to the power tool. The fuel tank housing has slots for air flow to heat the fuel tank to off-set the drop in fuel temperature due to latent heat of evaporation of liquefied petroleum fuels. Gaseous fuel may include LPG, Butane, LNG, H2, etc.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of priority of U.S. provisional application No. 61586840, filed Jan. 16, 2012 entitled “Gaseous Fuel Tank and Power Tool”, filed the entirety of which is incorporated by reference herein for all purposes. 
     
    
     BACKGROUND 
       [0002]    In conventional gasoline fueled engines used in hand-held applications, such as in chainsaws, trimmers, and blowers it is desirable to keep the engine generated heat away from the fuel tank, as it is not desirable to heat the fuel tank and gasoline fuel. However, it is desirable to keep the fuel tank and or the tank assembly of the gaseous fuel, particularly the liquefied gaseous fuel, such as LPG (propane), Butane, LNG, and similar fuels warm at about 50 to 110 deg F., which is the ambient temperature and is range when the customers use outdoor power tools such as trimmers, chainsaws, etc. The liquefied gaseous fuels, which are in gaseous state under ambient pressure and temperature conditions are stored in liquid form at ambient temperature, but at above the vapor pressure of the fuel. As the fuel is used up during the running of the engine, the temperature of the fuel in the fuel tank drops due to latent heat of evaporation of the fuel, as result, the pressure in the fuel tank reduces with reduction in temperature and eventually it is possible that the frosting on the fuel tank will be such that the fuel pressure may drop to such a level that the engine no longer runs properly due to lack of correct air-fuel ratio. Because the fuel density changes with pressure and temperature, the open loop carburetor may perform poorly if the supply pressure is not consistent. However, the pressure in the fuel tank continues to remain constant as long as the heat lost due to evaporation is made up by the heat transmitted to the fuel tank from outside, either due to convection, radiation, and or conduction. In order to transmit heat from the engine, the location of the fuel tank becomes critical, particularly when electrical and liquid coolant is not used to heat the tank. In portable tools, size and weight are also critical and as such the fuel tank has to be located and packaged to optimize the size and weight. Secondly, the size of the fuel tank dictates the dimensions of the power tool. A compact size is critical for certain applications, such as hedge trimmers, hand held blowers, and chainsaws. It is even more critical in chainsaws, where they are commonly used on trees and as such it cannot be unduly heavy and over sized as the overall operating attitudes change and areas where it is operated is typically very congested. The embodiment described here addresses such requirement for a gaseous fueled power tool. The embodiment here describes location and attitude of the LPG fuel tank for a chainsaw as an example, and similar designs can be applied to other types of portable power tools. The embodiment also describes where the ambient air is used to warm the fuel tank during operation of the tool. The ambient air going past the fuel tank gets cooler than the ambient air, which is in turn, is used to cool the engine. A fraction of the cooling air is drawn through the fuel tank assembly and mixed with ambient air to cool the engine. Alternatively, a fractional amount of cooling air past the engine, which is hotter than the ambient air can be used to warm the fuel tank. Secondly, a bi-metal switch may be used to regulate the heating air used for warming the fuel tank. Thirdly, the frame holding the fuel tank may transfer fractional amount of heat to warm the fuel tank, while major fraction of the heat from the frame may be removed by the cooling air, such that an equilibrium of heat may be maintained in the fuel tank, that is the heat of evaporation is made up by the fractional heat transfer from frame to the tank. The heat transfer from the frame to the tank may be through a special vibration dampening material such as rubber made up of certain chemical composition. To achieve the desirable goal of keeping the fuel tank from frosting, the embodiment describes the location and attitude of the fuel tank. The fuel tank is arranged to receive heat from the ambient air or from the cooling air. The mounting of the fuel tank is also described. 
       SUMMARY 
       [0003]    Various embodiments describe the location, attitude, method of clamping, fuel tank assembly, and method of heating the liquefied gaseous fuel tank in a portable power tool. Examples of the liquefied gaseous fuel having ranges of vapor pressure and latent heat of evaporation are; H2, methane, LNG, LPG, pure propane, butane, or a mixture of propane and butane. Small two and four-stroke engines are commonly used in many applications such as in hand held power tools, portable lawn and garden applications, and scooters, etc. The gaseous fuels have significant advantage over gasoline or diesel type of liquid fuels. The gaseous fuels are cleaner and have significantly lower engine out emissions in comparison to gasoline fuel. Gaseous fueled small engine are commonly used in lawn and garden tools such as chainsaws, trimmers, blowers, pumps, and also for personal transportation such as scooters. 
         [0004]    Various embodiments describe the location and attitude of the gaseous fuel tank assembly particularly for warming the fuel tank and also from point of view overall size of the power tool, and easy access to reload the fuel tank. In the embodiment disclosed an On-Off f fuel valve is also disclosed. One example of location of the fuel tank assembly in a chainsaw is above the cooling fan (fly wheel) and closer to the starter assembly. Another example can be closer to the carburetor where the axis of the fuel tank is significantly parallel to the axis of the crankshaft or is at an angle but in a plane significantly parallel to the axis of the crankshaft. Further another location can be where the fuel tank assembly is attached to the handle of the chainsaw, which is commonly isolated from the engine block through vibration dampeners to minimize the vibration of the handle. The fuel tank assembly may be attached to the handle at many different angles that provides for compact size of the tool. Further, the fuel tank assembly may be integral with the engine housing and or the handle. The fuel tank assembly having a metal case may be over molded with the engine housing or the handle for cost and size. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a left side view of a chainsaw having fuel tank assembly on top left. 
           [0006]      FIG. 2  is a sectional front view of the chainsaw  100  shown in  FIG. 1 . 
           [0007]      FIG. 3  is a left side view of a chainsaw  200  having fuel tank behind the engine block. 
           [0008]      FIG. 4  is a top view of the chainsaw shown in  FIG. 3 . 
           [0009]      FIG. 5  is a left side view of a chainsaw  300  having fuel tank on the left front side of a chainsaw. 
           [0010]      FIG. 6  is a sectional view of the chainsaw shown in  FIG. 5 . 
           [0011]      FIG. 7  is a top view of fuel tank assembly  900  having a shut-off valve. 
           [0012]      FIG. 8  is a sectional view of the fuel tank assembly  900  shown in  FIG. 7 . 
           [0013]      FIG. 9  is a cross sectional view of the fuel tank assembly  900  and the chainsaw  500  with fuel tank behind the crankcase and away from the CL of the cylinder. 
           [0014]      FIG. 10  is a side sectional view of a (top handle) chainsaw  600  with chain bar significantly in line with axis of the cylinder and fuel tank between the carburetor and the chain bar. 
           [0015]      FIG. 11  is a side sectional view of a (top handle) chainsaw  700  with chain bar significantly in line with axis of the cylinder and fuel tank between the carburetor and the axis of the cylinder and is closer to the spark plug. 
           [0016]      FIG. 12  shows top view of the chainsaw  700  shown in  FIG. 11 . 
           [0017]      FIG. 13  shows line diagram of a dual plunger oil pump delivering two different types of oils and at different rates of each type of oil. 
           [0018]      FIG. 14  shows front sectional view of a chainsaw having axis fuel tank in parallel to axis crankshaft attached to the base frame  368 . 
           [0019]      FIG. 15  shows front sectional view of a chainsaw having at least two fuel tanks and their axis is perpendicular to axis of crankshaft but in a different plane in a plane below the plane of the crankshaft and attached to the base frame  368 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The following are hereby incorporated by reference herein for all purposes: U.S. Pat. Nos. 5,884,460, 5,918,574, and 5,606,944, 5,701,855, 4,924,822, 2,829,251, and Publication number 2011/0088650 A1. 
         [0021]      FIGS. 1 , through  6  show a portable power tool having various embodiments of locations and attitudes of a gaseous fuel tank and having features to warm the fuel tank and or the assembly. U.S. Pat. No. 5,884,460 describes a method of mounting a propane fuel tank on the handle of a lawn mower. The drawback of the disclosure is that the fuel tank is mounted farther away from the heat generating internal combustion engine. As such this method of holding the fuel tank and location does not address the problem associated with the frosting on the fuel tank which affects the performance of the engine significantly.  FIGS. 6 and 7  show location of the fuel tank in a chainsaw and a hedge trimmer, which again is farther away from the heat generating engine and secondly does not address the problem of frosting on the fuel tank, as the tanks are not properly encased in a fuel cage/frame that help in transmittal of heat from the ambient air or from the engine. U.S. Pat. No. 5,606,944 describes where the fuel tank is heated by the fully heated cooling air passing through the entire cylinder block  605  and cylinder head  628 . The drawback is that during hot summer days when the ambient temperature is 105 deg F. or so, the temperature of the cooling air may exceed 250 deg F. and over heat the fuel tank. Secondly, fuel tank on the outlet side of the cooling air may obstruct the free flow of the cooling air. 
         [0022]    Various embodiments overcome drawbacks and improve upon the above prior arts. The operating principle of the innovative locations and attitudes disclosed in the present embodiments are only a few examples. As such it will be understood that a person who has knowledge of engines will be in a position to execute the embodiments disclosed herein. 
         [0023]    Turning to  FIGS. 1 and 2  of the presently disclosed embodiments, chainsaw  100  consists of a cylinder  12  inside which is a reciprocating piston  16  connected to a crankshaft  22  through a connecting rod  18 , a crankpin  20  and a piston pin  114 . The crankshaft  22  has crank weight  21  and the crankshaft is supported by main bearings  22   a  and  22   b.  The crankshaft  22  is supported on both ends in a full crank engine, or on just one side in a half crank engine. The lower side of the piston has crankcase chamber  26  in the crank case  28 . The cylinder  12  has cylinder bore  14  having combustion chamber  30  on the upper side of the piston  16 . The crankcase chamber and combustion chamber are interconnected periodically through transfer passage  11 . The cylinder has at least one intake port  84 , exhaust port  50 , and at least one transfer port  33 . The lubricating system consists of an oil pump  802  driven by the crankshaft  22 , typically mounted to the side of the crankcase wall. Oil pump  802  has an inlet oil line  806  and receives oil from oil tank  808 . Oil pump  802  also has an outlet pipe  803  for injecting oil into the intake and another outlet  803  to lubricate the chain  353 . The oil pump  802  may be of double acting, in the sense that it can have two inlets and two outlets to supply two different types oils to lubricate the engine and the chain with respective types of oil and rate. The cover  358  on left side of the chainsaw consists of a starter assembly  359  having open slots  618  ( 618   a,    618   b,    618   c ), for inlet of ambient air to cool the engine block, including cylinder  12  and cylinder head  44 . The cover  358  shown in  FIGS. 1 and 2  has slot  618   c  receiving cooling air  522   m  from the outlet of the fuel tank assembly  500 . Fuel tank assembly  500  consists of the replaceable LPG or Butane fuel tank  2007 , which are typically cylindrical in shape, having height bigger than the diameter, circumferentially and intermittently spaced supporting members  508  around the tank  2007 , a metal casing  506 , and plastic housing  504  having at least one open slot  512   a  for ambient air and at least one open slot  512   h  for warmer engine air to circulate around the fuel tank  2007  and the fuel tank assembly having an outlet  5120  leading into the open slot  618   c  in the cover  358 . The ambient air  522   c  entering the open slot  512   a  and fraction of the air that has passed through the cooling fins  126  of the engine cylinder  12  and cylinder head  44  entering the open slot  512   h  pass around the fuel tank  2007  transferring heat to the fuel tank  2007 . Thus making up for the latent heat of evaporation of the fuel and maintaining a reasonable constant temperature of the fuel tank. The air passing around the fuel tank  2007  before exiting transfers heat to the cooler fuel tank  2007 . The amount of air entering the open slot  512   h  on the engine side is regulated by the bimetal valve  620 . As the engine gets hotter, temperature of the air entering the open slot  512   h  increases, as a result of increase in temperature of the air, the bimetal valve  620  restricts the hot air flowing through the open slot  522   h.  Thus a smaller fraction of hot air now flows through the open slot  512   h  to prevent over heating of the fuel tank  2007 . 
         [0024]    The embodiment disclosed in  FIGS. 1 and 2  show that the fuel tank assembly  500  is located above the cooling fan  29  and in the segment between the vertical axis CL of the cylinder  12  and the center line  222  of the crankshaft  22 . The fuel tank assembly  500  is located below the top level of the handle  353 , thus the overall height of the gaseous fueled chainsaw is same as a gasoline fueled chainsaw. The embodiment also shows that the fuel tank assembly  500  having a elements  519   a  and  519   b,  which are metal tabs extended from the metal casing  506  are attached to a section of the cooling fins  126   a  and  126   b  to transfer heat from the cylinder  12  to the fuel tank  2007  through convective heat transfer by the air between the casing  506  and the fuel tank  2007 . The heat is also conducted to the metal casing  506  and the fuel tank  2007  through the supporting members  508 . Therefore the amount of heat transferred from the fins to the fuel tank can be determined by the area of contact between the elements  519  and fins  126 . The Chainsaw  100  has a top cover  355  and cover  363  on the right side of the chainsaw. The top cover  355  may house a fraction of the fuel tank assembly  500  by having a curvature  355  to conform to the shape of the fuel tank casing  504 . Alternatively, the plastic housing  504  may be integrally molded to the top cover  355  and the fuel tank  2007  may be clamped to the fuel tank housing  504  by means of at least one U strap/clamp  722 , as used in many applications and similar to the one disclosed in prior art U.S. Pat. No. 2,829,251 and another being a method to fasten larger LPG tanks in a fork lift as disclosed in U.S. Pat. No. 5,330,031. Alternatively, a end cap  525 , as described in prior art U.S. Pat. No. 5,606,944, may be used to hold the fuel tank  2007  in place.  FIG. 1  also shows an On-off valve  205  to shut of the fuel when the engine is not running. The shut off valve  205  may be affixed to the fuel tank assembly  500 . The on-off valve also be an integral with a primary pressure regulator. Pressure regulators are used to reduce the high pressure in fuel tank to lower pressure such that the supply pressure to the carburetor is lower. Also, the primary pressure regulator may be attached to a heat sink, such as cylinder head or cylinder cooling fins  126  or crankcase  28  so that the liquid fuel is converted to vapor. The connection between the fuel tank  2007  and the fuel shut-off valve  205  may be just a press fit and where the fuel tank is held in place by an end cap  525 , as described in prior art U.S. Pat. No. 5,924,400 and or a threaded connection as used in most 1 lb fuel tanks sold in US. The threaded fuel tank may directly be screwed on to the pressure regulator cum on-off valve assembly as used in most pressure regulators used in Asian countries (reference to be provided) and shown in  FIGS. 7 and 8 . Just the threaded type connector  904  without the pressure regulator  910  may be mounted on a dampening material  920 , such as rubber pads to minimize the transfer of vibration from the engine frame to the fuel tank  2007 . In which case, there may be a small section of flexible fuel hose  207   a  between the fuel tank assembly/pressure regulator  900  and a metal pipe  207 . Metal pipe may then be attached to engine for receiving heat to vaporize the fuel. 
         [0025]      FIGS. 3 and 4  show another embodiment showing the location of the fuel tank  2007  in a chainsaw  200 . In this embodiment the fuel tank assembly  500  is located horizontal in a plane substantially parallel to the plane passing through the axis  222  of the crankshaft  22 . The fuel tank assembly is located behind the engine block  102 , away from the chain  354 . The fuel tank may be at an angle with the fuel outlet pointing upward. It is also possible for the fuel tank to be attached to the crankcase wall  28 , as described in a prior art published in US2011/0088650,  FIG. 4   f , but in this new embodiment, the axis  2007   a  of the fuel tank  2007  and the axis  222  of the crankshaft  22  are substantially parallel to each other. It is possible for the fuel tank frame  504  to be integrally molded with the base  528  of the chainsaw. Secondly it is possible for at least one of the metal tabs  519   a  or  519   b  to be attached to the crankcase  28 , as shown in the prior art U.S. Pat. No. 5,606,944. The fuel tank  2007  may be held in place by means of U straps  722 , which may in turn be affixed to the base  528 , or may have an end cap  525 , particularly when the housing  504  is integral with the base  528 . 
         [0026]      FIGS. 5 and 6  show another embodiment  300  where the fuel tank assembly  500  is substantially vertical attitude. The fuel tank assembly  500  may be clamped to the handle  353 , or may be attached to one of the side covers  358  or  363 .  FIG. 5  shows here the fuel tank assembly  2007  is toward the front of the crankshaft  22  in a vertical attitude. Alternatively, the fuel tank may also be located toward the back of the crankshaft  22 . The attitude of the fuel tank  2007  may be at an angle on a plane perpendicular to the axis  222 . When the fuel tank  2007  is mounted to the handle  353 , which is isolated from the engine to minimize vibration, flexible fuel supply line may be used to supply fuel to the carburetor  400 . Alternatively a metal pipe  207  may be used as shown in  FIG. 1 , and the fuel line may be attached to the engine or disposed around the cooling air outlet to heat the fuel line for vaporization of fuel, as described in prior art U.S. Pat. No. 5,924,400. In another embodiment, there can be more than one fuel tank attached to the tool for extended use of the tool. The location of multiple fuel tanks can be a combination of different locations and attitudes.  FIG. 6  shows an oil pump delivering two separate types of oils; one to the engine and the other to the chain from two different oil tanks  806   b  and  806   c.  Since the characteristics of the oils are different for chain and engine, it may be necessary to have separate oil tanks. A single oil pump with one plunger with different plunger diameters for two different oil delivery rates may be employed. However, oil common to both; the chain and engine may also be used requiring only one oil tank  806 , as shown in  FIG. 2 . 
         [0027]      FIGS. 7 and 8  show another embodiment of the fuel tank assembly  600  having a connector assembly  900  with a vibration dampening bushing  920  between the fuel tank housing  504  and the connector assembly  900 . The connector assembly  900  has a threaded collar  904 , which is used with fuel tank  2007  having a threaded outlet  2009  as used in 1 lb LPG tank, or a press fit type as used in certain type of Butane tanks, an arm  906 , which may have built in on-off valve  912  and optional pressure regulator  910 , and having a flexibly fuel hose  207   a.  The arm  906  is mounted on to the fuel tank housing  504  through vibration dampening bushing  920 . The advantage with this embodiment is that when the fuel tank is threaded on to the collar, the collar can self align with the outlet  2009 . Secondly the connector assembly  900  may be rotated to about the arm  910  if a hinged type fuel tank assembly is used, for easy replacement of the fuel tank  2007 . As before the fuel tank assembly  600  can be attached to the power tool at any attitude and locations. 
         [0028]      FIG. 9  shows a cross sectional view of a power tool having the fuel tank assembly  500  behind the crankcase  28 . The center line  2007   a  of the fuel tank  2007  is substantially parallel to the axis of the crankshaft  22 . It may be noted that the fuel tank housing  504  is located below the carburetor  400  and in the segment between the carburetor and the centerline CL of the cylinder in a plane farther from the center line CL of the cylinder. Angle A describes the segment within which the fuel tank  2007  may be located for compact size of the power tool. Angle A is between the line passing through the axis  222  and the bottom most point of the carburetor  400  and line passing through the axis  222  and that tangential to the fuel tank  2007 , as shown in  FIG. 9 . Angle A is about 135 degrees. Also, it should be noted that the metal casing  506  may be attached to the engine block, specifically the crankcase flange  28   c  or cylinder flange  12   c  or it can be sandwiched between the cylinder flange  12   c  and the crankcase flange  28   c.    
         [0029]      FIGS. 10 and 11  show, what is commonly known as top handle chainsaw, in which the base housing  328  is not present, but has at least one top handle  353   b,  preferably running from the top of the engine (spark plug side) toward the chain (crankcase side). As shown in the embodiments, the chain bar  815  is typically in line with the axis CL of the cylinder, but can be at a very small angle, less than 45 degrees, and the chain bar is farther from the spark plug. In such engines, the exhaust port  50  is typically at about 90 degrees from the intake port  84 . These type of engines have a displacement less than 38 cc.  FIG. 10  shows the chainsaw  600 , where the fuel tank  2007  is in from of the carburetor  400 , but toward the crankcase  28  and the chain bar  815 . Part of the metal casing  506  of the fuel tank assembly  500  may be partially integral with the crankcase  28  and partly integral with the cylinder  12 . Alternately, the flanges  12   c  and  28   c  may conform with the necessary curvature of the metal casing  506 . Secondly the metal casing  506  need not be fully wrap 360 degrees around the fuel tank  2007 . Also, as shown the top handle  35   b   3  can be integrally molded with the fuel tank housing  504 . 
         [0030]      FIG. 11  shows the chainsaw  700  where the fuel tank  2007  is located closer to the spark plug  44   b  and behind the carburetor  400 . The fuel tank assembly  500  is farther away from the chain bar  815 . Alternately, the fuel tank  2007  may also be located below the park plug  44   b,  closer to the muffler (not shown). Typically the exhaust port  50  is away from the plane of the paper (above) and starter assembly is below the plane of the paper. In Chainsaws  600  and  700 , the axis  2007   a  of the fuel tank  2007  is significantly parallel to the axis  222  of the crankshaft.  FIG. 12  shows top view of the embodiment shown in  FIG. 11 . 
         [0031]      FIG. 13  shows line diagram of a oil pump  802  having a plunger of two different diameters to deliver different types of oils, one for the engine and the other for the chain. The pump is driven by the crankshaft  22 . However, it must be noted that the gaseous fuel may have a pre-mixed oil in the container as disclosed in U.S. Pat. No.  5 , 701 , 855 . 
         [0032]    In another embodiment, the fuel tank assembly  500  may be located closer to the exhaust muffler of an engine so as transfer heat from the muffler through radiation and convection. The size of the fuel tank can range from 2.0 oz to 20.0 oz. The fuel tank  2007  may be made of aluminum, steel, or carbon fiber. 
         [0033]      FIG. 14  shows another embodiment where the fuel tank  2007  is attached to the base frame  368 . And the axis of the fuel tank  2007   a  is substantially parallel to the axis  222  of the crankshaft. Also, it is possible to have more than one fuel tank to be attached in a similar manner, where the axis of the fuel tank is parallel to the axis of the crankshaft. 
         [0034]      FIG. 15  is similar to the embodiment shown in  FIG. 14 , but the axis  2007   a  of the fuel tank  2007  is now substantially perpendicular to the axis  222  of the crankshaft  22 . 
         [0035]    It must be understood that the embodiments disclosed here are not limited to chainsaws, but also applicable to hand held blower, back pack blower, back pack trimmers, water pumps, compressors, generators, go-peds, scooters, cultivators, edgers, hedge trimmers, etc. Also, the fuel tank assembly  500  may be attached to the starter housing  353 , while the chain and clutch is replaced with blower fan as used in blowers or any transmission case for transportation applications. 
       PARTS LIST 
       [0000]    
       
           100  Chainsaw 
           102  Engine block consisting of cylinder, crankcase, a crankshaft, and a muffler 
           4  Ignition coil 
           11  Transfer passage 
           12  Cylinder 
           12   c  Cylinder flange 
           14  Cylinder wall 
           16  Piston 
           18  Connecting rod 
           20  Crank pin 
           21  Crank web 
           22  Crankshaft 
           22   b  Crankshaft bearing 
           22   a  Crankshaft bearing 
           26  Crankcase chamber 
           28  Crankcase 
           28   c  Crankcase flange 
           29  Cooling fan or Flywheel 
           30  Combustion chamber 
           31  Transfer port 
           44  Cylinder head 
           44   b  Spark plug 
           50  Exhaust port 
           53  Starter handle 
           84  Intake port 
           114  Piston pin 
           126  Cooling fins 
           126   a  and  126   b  Cooling fins 
           200  Chainsaw having fuel tank behind the engine block  102   
           205  On-off valve 
           207   a  Flexible fuel hose 
           216  Clutch drum 
           217  Clutch 
           222  Crankshaft axis 
           328  Base Housing 
           328   b  Base Handle 
           353  Handle 
           353   b  Top handle 
           354  Chain 
           355  Top cover 
           355   b  Recess in top cover  355   
           358  Left side cover 
           359  Starter assembly 
           363  Right side cover 
           368 ,  528  Base 
           400  Gaseous fuel supplier/Carburetor 
           410  Plunger 
           414  Cut out cam 
           500  Fuel tank assembly 
           504  Fuel tank housing 
           505  Heating air outlet duct 
           506  Metal casing 
           508  Supporting member 
           510  Space between the metal plate and replaceable fuel tank 
           512   a  Open slot 
           512   e  Outlet passage 
           519   a  and  519   b  Metal elements attached to metal casing  506   
           522   c  Ambient air entering slot  512   a    
           522   h  Open slot for warmer cooling air 
           522   o  Outlet on fuel tank assembly 
           622   m  Cooling air (mixture of ambient air and air from passage  512   e ) 
           525  End cap 
           528  Base 
           614  Inlet to fan/flywheel 
           618 ,  618   a,    618   b,    618   c ) Open slot 
           615   a,    615   b  Open slot 
           620  Bi-metal valve 
           722  U Strap/Clamp 
           808  Oil tank 
           806  Oil inlet line to pump  802   
           806   c  Oil tank for chain oil 
           806   b  Oil tank for engine oil 
           803   c  Oil supply line to chain 
           803   b  Oil supply line to crankcase chamber