with initial reference to fig1 a portable pressure washer embodying the invention is represented generally by the numeral 11 . portable pressure washer 11 comprises a two - cycle internal combustion engine 12 contained in a housing 13 . a centrifugal clutch 14 is mounted to the output shaft of the engine , as described in more detail below . a clutch cowl or shroud 15 is bolted to the engine housing 13 in surrounding relation to the centrifugal clutch 14 . a rotary pump 16 is operably connected to the centrifugal clutch , and a cowl or shroud 17 bolts to the cowl 15 in protective surrounding relation to the pump 16 . a spray wand 18 is connected to the output of pump 16 and includes a spray head 19 for dispersing a spray of a predetermined pattern . more specifically , engine 12 is preferably of the two - cycle internal combustion type and may range in size depending on the application . the most important factor in this regard is that the engine be large enough to effectively drive the pump but small enough to carry . the size of engine 12 in the preferred embodiment is 32 cc ( displacement ), which is approximately 1 horsepower . engine 12 is manually started through a retractable coil start 21 and includes an on - off switch 22 . a conventional fuel tank 23 having a removable cap 24 is mounted to the housing 13 through a pair of coil springs 25 , only one of which is shown in fig1 . the coil springs 25 isolate the fuel tank 23 and handle 26 from vibration of the engine 12 . housing 13 further comprises a downwardly projecting leg 26 which supports the pressure washer 11 when it is placed on the ground or another supporting surface . the device may be tilted rearwardly so that the spray head 19 does not come into contact with the ground . a d - shaped handle has one end mounted to the front side of fuel tank 23 . in the preferred embodiment , the fuel tank 23 and handle 26 are integrally molded from plastic . the opposite end of handle 26 is loosely bolted to an upwardly projecting ear 27 on clutch cowl 15 . preferably , this loose bolting is accomplished through a rubber grommet 27a which , with the coil springs 25 , isolates the handle 26 and fuel tank 23 from engine vibration . a trigger 28 is operably mounted on handle 26 to operate the engine carburetor ( not shown ) in a conventional manner , permitting the user to vary the speed of engine 12 between idling and maximum speeds . with reference to fig2 engine 12 has an output shaft 29 , and centrifugal clutch 14 is mounted to the shaft 29 through the use of a nut 30 and washer 31 . centrifugal clutch 14 includes a drive portion 32 ( the portion mounted to shaft 29 ) and a driven portion 33 which takes the form of a bell housing . drive portion 32 includes a hub 32a , a circumferential coil spring 32b and radially expandable centrifugal weights 32c . at a predetermined rotational speed of engine 12 and shaft 29 , the weights 32c expand radially outward by centrifugal force against the bias of spring 32b and engage the bell housing 33 in clutching relation , causing the bell housing 33 to rotate . with reference to fig1 clutch cowl 15 includes a pair laterally projecting ears 34 ( only one of which is shown ), and the cowl 15 is bolted to the engine housing 13 with screws ( not shown ). with continued reference to fig2 rotary pump 16 is of the positive displacement type . the preferred embodiment employs a vane type pump manufactured by procon products , division of roehlen industries of murfreesburo , tenn . pump 16 includes a shaft 35 to which the bell housing 33 is mounted through a set screw 36 . pump 16 includes a housing 37 , and shaft 35 is rotatably carried by a bearing 38 at one end and by spaced front and rear bearings 39 , 40 at the other . disposed between the bearings 39 , 40 is a stationary annular liner 41 defining a cylindrical pump chamber . a rotor 42 is rotatably mounted on the shaft 35 and disposed in the chamber between the front and rear bearings 39 , 40 . rotor 43 carries four equiangularly spaced vanes 43 , each of which slidably engages the inner surface of annular liner 41 . a spring loaded seal assembly 44 compresses the front and rear bearings 39 , 40 relative to the annular liner 41 , and o rings 45 also assist in sealing the unit . an end plate 46 is held in place by a split ring keeper 47 and retains the assembly . the opposed inner faces of the front and rear bearings 39 , 40 are contoured ( not shown ) to define porting channels respectively connected to a pump inlet 48 and outlet 49 ( see fig1 ), each of which compromises an internally threaded bore . an elbow 50 is threaded into the inlet 48 , and a flexible hose 51 is secured to the elbow 50 . a conventional coupling 52 on hose 51is adapted for connection with a conventional garden hose ( not shown ). the vane pump used in pressure washer 11 is normally intended for direct coupling to an electric motor that rotates in a first direction at an operating speed of 1 , 725 rpms . internal combustion engine 12 of the preferred embodiment has an operating speed of approximately 6 , 200 rpms and rotates in a direction opposite that of an electric motor . nevertheless , pump 16 may be operated in a reverse direction because it is of the vane type through minor porting modifications , and the increased rotational speed has been found not to have an adverse effect on pump life relative to the anticipated life of engine 12 . at 6 , 200 rpms , pump 16 produces approximately 2 . 6 gallons per minute at 220 psi . should pressure in the system increase to 300 psi , pump 16 operates in an internal bypass mode . pump cowl 17 is screwed to the clutch cowl 15 through the use of a plurality of screws not shown . it includes an aperture 53 that registers with the pump outlet 49 when the components are assembled . spray wand 18 compromises a long , substantially rigid tube that is externally threaded at its inner end 54 to project through the aperture 53 and into threaded engagement with pump outlet 49 . a secondary handle 55 is mounted on wand 18 for use with primary handle 26 . a rubber bushing 56 is disposed between handle 55 and wand 18 to reduce vibration to the users hand . spray head 19 is conventional and threadably mounted to wand 18 to permit interchangeability with other spray heads to obtain a desired spray or jet pattern . the overall weight of portable pressure washer 11 in the preferred embodiment is approximately 12 . 5 pounds . a two - point shoulder strap ( not shown ) may be connected to pressure washer 11 to assist carrying it during operation . in operation , a garden hose connected to a faucet ( neither of which is shown ) is connected to the coupler 52 , and the faucet is then opened . on - off switch 22 is then moved to the &# 34 ; on &# 34 ; position and engine 12 is started with the retractable coil start 21 . in the preferred embodiment , centrifugal clutch 14 engages at approximately 4 , 000 rpms , which is higher than the idling speed of the engine 12 . as such , the drive and driven portions 32 , 33 of clutch 14 are disengaged when engine 12 is started , thus avoiding the additional load of pump 16 . engine speed may be increased and decreased with trigger 28 , which is operatively connected to the engine carburetor , and when the engine speed exceeds approximately 4 , 000 rpms drive portion 32 clutchably engages driven portion 33 resulting in operation of pump 16 . as long as this engine speed is maintained , water received from inlet 48 will be delivered by pump 16 to the spray head 19 under pressure . as soon as trigger 28 is released and engine speed drops below 4 , 000 rpms , clutch 14 disengages and pump 16 ceases to rotate , interrupting the flow of pressurized water at the spray head 19 . operation of pressure washer 11 may continue on demand so long as engine 12 is running and pump 16 receives a supply of water through its inlet 48 . when spray operations are completed , engine 12 is turned off with switch 22 , the hose faucet turned off and hose removed from the coupling 52 . pump 16 is self draining through hose 51 and coupling 52 if they are maintained at a lower position than pump 16 . based on the foregoing , it will be appreciated that portable pressure washer 11 is relatively light weight and thus easy to use , and coupling the engine and pump through a centrifugal clutch provides a number of advantageous functions including simplified engine starting , operation of the pump on demand , and interrupted operation of the pump when the engine is idling .