' FUEL ENRICHMENT SYSTEM FOR CARBURETORS FOR INTER AL
COMBUSTION ENGINES -
FIELD OF THE INVENTION
[0001J The- present invention relates to internal combustion engines. In particular, ths present invention relates to fuel enrichment systems far carbur -tors for internal combustion engines,
BACKGROUND OF THE INVENTION
[0002] Internal combustion engines require a. higher proportion of ft el in the .fuel/sir mixture produced in fee carburetor (eatichment) during engine start-up -ranking speeds to provide easier starting of the engine. Curreatly, in standard internal combustion engines there are two primary methods of providing the correct fual enrichment during start-up.
[0003] The first method is by the manual or electrical activation of a choke plate. The choke plate is located within the intake bore of the carburetor and can he opened or closed to allow the desired amount of air to flow into the intake bore "When opened, the choke plate completely opens the intake bore and allows the si to flow therethrough. When closed, the choke plate blocks the intake bore except for he ies in the choice plate, which have sufficient area to allow a predetermined amount of a- r to flow into the intake bore to create proper enrichment for start-op.
[0004] One drawback to this method of fuel enrichment is that i requires operator interaction. If an engine is difficult to start, the operator must close he choke plate completely to properly enrich the engine for startup. If tlie choke pi :.te Is not completely closed there may not be enough fael provided to the carburetor and - the engine will continue- to be difficult to start. In addition, once the engine is running the ■ operator must rememberto open the choice plate, or the engine will continue to this in the enriched condition which leads to rougli running. A second drawback to this laetLv-i of ftiel aarichm&nt is that, it can also be prone to over earichment such as if ths some o all of the boles in the choice plate become blocked, or under OBtichiasat, such as if the c tofcs plate is not completely closed Qvsi mdcbzizzi can cause hard starting ssd;or plug i. wlaing.
[00§S] Tlie szzjthi meeiod h by m-ouul or ecrrioal actiration c" a primer bulb. The primer bulb is typically internl to the- oarburetor body OT rsraotely r -vou^ied ro the engiae assembly. Wizen me primer bulb is p'^Bpad, air or fuel ptess>ire U ^rc-ed into the fuel circuit tmsfting the fael into the carburetor throttle bore.

(0006) However, each of these methods have their oWH particular drswbascks. The first main drawback with the old methods of fuel enrichment Is that >perator interaction is required. When manually activated both of the above methods can result in not enough feel haing orcvidsd to the carburetor and therefore cause difSeultv in start-up. The second main drawback is that both, of the above methods are prone to over enrichment causing hard starting and/or plug fowling ox un£er enrichment. Both *»f which, prevent easy starting of the engine.
[0007] It would therefore he advantageous if a fuel enrichment syst ym for a carburetor of an internal combustion engine could be designed that does BO require operator interaction and avoids the problem of over or under eBxickmeat
SUMMARY OF THE INVENTION [OOOSJ One aspect of the present i&ventitm is a carburetor for ar internal
comb&3tK>R engine having a body. A first end of the body fastens to an air fi] rer aad a second end of the body fastens tc an. intake port af a cylinder head An iniako bore Is foxmed in "die first and and a throttle "bore is formed in the second end- A - -enturi is foimed between and interconnects the intake bore and the throttle bore, A bar ■- extends fiom the ventari through the body to provide fad to the veatuxi. A fuel bowl .135 walls xlM define m internal volume and Is fastened to ihe body, A foel enridimaiit system is responsive to ths vibratiou of the engine and im a passage that is formed in he body, The passage ha> an inlet that comimmicates tvith. the intake bore and an c utiet that communicates with the bore* The fuel eflriclunent system prevents the ftrV of air through the passage whsu the engine is at speeds less than idle speed. wA allow ^ the flow of air through the passage when the eagias is_ at speeds greater than cranking speed!OG09I This provides the correct fuel enrichiaant dtixfne: engine 5tml-up ""ithout Grerator interveritiort prevente the problems of ever or ^Kfer er>rk am^Rt by providing for a pxederenriiad fusl/ak mixture during startup. and aHows ^jnic]. and easy engine starting.
BRIEF DESCRIPTION OF THE DRAWINGS [0010] Fig, 1 is a first perspective view of a single cylinder engine, aken from
a side of the engine on. which are located a starter and cylinder head.
[0011] Fig. 2 is a second, perspective view of the single cylinder enj ine of Fig.
i r talcen fi:oni a side of the engine oa which are located aa air okansr aa& oil S sr.

[0012] Fig. 3 is a third perspective view of the single cylinder engine of Fig. L in which certain parts of the engine have been removed to reveal additiona. internal parts of the engine.
[0013] Fig. 4 is 3 fourth perspective view of the single cylinder sngu a of Fig. U in wbich eertaiu parts of the engine have been removed to reveal additioaa internal parts of the engine.
[0014] Fig, 5 is fifth perspective view of portions of the single cylind :T engine of Fig- 13 in which a top of the craokcase has-been removed to reveal an inter or of the crankcase.
[00151 < Fig. 6 is a sixth perspective view of portions of the single cylinder engine of Fig. 1, in which the,top of the crankcase is shown exploded firom the 1 ] Fig. 10 Is a front view of the carburetor of the single cylinder engine of
Fig, 1-
[0020] Fig. 11 is a cross sectional view of the carburetor of Fig. 9 tsicen along
line A-A-
[0021] Fig, 12 is a cross sectional view of the carburetor of Fig- 9 fe £en along
lineB-B.
DETAIL£D DBSCfUJTICHS! OF 1'HE P'RJEFERSED BMB0DIMSN1 [0022] Referring to Figs.. 1 and. 2, a single sjiindcr. 4-strokr. interns] eoinhastion engine 100 designsd by Koliier Co, of Kobkr, Wisconsin i-icmdes a crautccass 110 having a. cylinder 160 formed in a sidewall of the crankcase 11 \ a, cover 290 fastened to the top of Hie craatcase 110, and a blower housing 120 xnomite I on top of tiie covor 290, Inside of the blower housing 120 are a fen 130 and a tlywhed 140, The engine 100 further includes a starter 150 mounted to tte coyer 290 and a cylinder head 170, which has a proximal end fastened to the crankcase 110 aad extent s laterally outward from the sidewall of tike orarjkease 110 to terminate at a distal end. A rocker arm

cover 130 Is fastened to the distal ead of the cylinder head L70 an-i defines a cavity iterein which fonas a valve box, which houses the valves and other componer is of the valve train, which are discussed in more detail below. Attached to the cylinder; ysad 170
are an exhaust port 190 shews hi Fig. 1 and an intake port 200 shown in. Fig, 3.
[0023] As is well known in the art, during operation of the engine 100, a piston 210 (see Fig. 7) moves back and forth, within the cylinder 160 towards j ad awsy from the cylinder head 170. The movement of the piston 210 ia turn causes rot; doa of a crankshaft 220 (see Fig. 7), as well as rotation, of the fan 130 and the flywheel 1* O, which. are coupled to the crankshaft 220. The rotation of the fan 130 cools the engine. and tbs rotation of the flywheel 140. causes a relatively constant rotational xnom.sno m to be maintained.
[0024J Referring specifically to Fig, 2, the engine 100 further includes a carburetor 600, coupled to the intake port 200, and aa air filter 230 coupl xl to the carburetor 600, -as described in more detail below.' The air filter 230 filte '5 the air required by the engine prior to the providing of the air to the carburetor 600. Ai ■ from the air filter 230 is mixed with fud within the carburetor 600 to create an fuei/air m dure that is- then provided from tfro carboeior. 600 to the intake pott 200. The air/fa< [ mixtture provided to the intake port 200 is communicated into the cylinder 160 by v, ay of the cylin-head 170, and the exhaust from the cylinder 160 ££te the engiae t/ flowing from the cylinder 160 through the cylinder head 1?G and then out of the ediaiis port 190. The inflow of the air/foel mixture and outflow of this exhaust is governed b, ■ an input valve 240 and aa output valve 250T respectively (see Fig. S). Also as shown in Fig. 2, die engine 100 includes an oil filter 260 mounted to the cover 290, opposite the s arter 150, thro ash which the oil of the engine 100 is massed and filtered Specifically- tt ■& oil filter 260 IB coupled xo the crssko&se 110 In- wsv of coudim srd ouas^isa liB.es 270, 2?0. respectiveiy, whetsby presiUrted oil is prodded iato the oil filter 260 & d rhea is returned from the oil filter 250 to the crKokGass I! 0.
[0025] Rsfeni&g to Figs. 3 sad 4S the engine 100 is shown with ih*. blov/Pi hons2S2 120 r«£3.ove3 co sxoc^fe 3O"s: 295 of fee orsnircae 110. Wife rss; ecc to Fis;. i. m vMoh bctth. tL-5 5m 130^ai L!I6 fL;-v'h-ssl 140 rt z£so renewed a ooa 3;; j Is shcvs thai is xnonuted to the- oorsr 290 mi, snerates n electric- cirait Lsed -upon notation of the fea L3C aBd/or tiie Swfc.ael 140, wliioh togeiiisr operate as z magma A Iditiouafe the cover 290 of the crankcase U0 is shown to have a pair of lobes 310 that ■ -ore-.? a pair-

of gears 320 (see Figs. 5 and 7-8). Wife rsspeot to Fig. 4. the fan 130 and the : lywheei 14-0 sre shown above the cover 290 of the crankcase 110, Additionally, Fig. 4 si ows the engine 10G vidiout the cylinder head 170 md without the rocker ami cover ISO, to more dearly reveal a pair of tubes 330 throEgts. which, extend a pair of respective push, i >ds 340, Hie push, rods 340 extend betweezn a pair of respective rocker arms 350 and .* pair of cams 360 (see Fig. 8) within the crankcase 110, as discussed further below.
[0026] Turning to Figs. 5 aud 6, the engine 100 is shown with the c wer 290 removed from the crankcase 110 and Is shown in cut-away to exclude portions of the engine that extend beyond fee cylinder 160 suck as the cylinder head 170, Wit I respect to Fig. 6, Hie cover 290 of the crankcase 110 is shown above the camkcose 1L0 In £n e?:ploded view. The cover 290 and crapjcca.se 110 are manufactured as two separate pieces such that, in order to access the crmkcase 110, one physically removes he coyer 290 from the craofccase 110. Also, as shown In Fig. 55 the pair of gears 320 \ ithia the eraokcase 110 axe supported by and rotate "upon respective shafts 410, which, in turn are supported by tiie cranfccase 120.
[0027] Referring to Fig. 7, a top view of the engine 100 is provided in which additional internal components of the engine are-shown in'grayscale, taparticu or, Fig- 7 shovs the- pistoa 210 within the cylinder 160 to be coupled to &e crankshaft 220 by a coanectiiig rod 420. The- crankshaft 220 is ra turn coupled to a rotating cour reiweigfet 430 and reciprocal weights 440, which, balance the forces exerted upon the eras! obafi 220 by the piston 210. The crankshaft 220 further is in contact with each of the rssrs 320:, and thus comniiuiicates rotatiooai motion to the gsars. In the present embod ment, the shafts 410 npan. ~wluch. the gzzxs 320 are aipporied are capable of comniuaicatir. ,z oil frotn tic bottom of the cratjfe^e i 10 u-Dv/sr-3 to :h.e gears 320. The incoroine Hue .[.70 la the oil filler 260 is coupled to cn^ of the shafts 410 to receive oil ^4ik tbe outgon z line 2$K> from the oil filter Is coupled to the crsnisiiaii 220 to provide tobricsiiox ftiere ;.a. Fig. 7 further shows a spsrk plug 450 located on the cylinder tead 170, which provi ies sparks miring power strokes of fee SEigiiie to oazise ca-Hhustion to ocour within ihe o}r ind&r 160. The electrical energy for the spsrk ptog 450 is provided by ths ceil 300 (see Vn. 3),
[0028] Fimiier referring to Fig. 7y and additionally to Fig- 8, ek aents of a valve train 500 of the engine 100 are shown. The vai-ve teain 500 includes the gaars 320 lesdag upon the shafes 410 and also includes tbe cans 360 imdemeatb the gears. r5::-c"e-f;'". AddtnGnsifv, :&e-sti.T5 i-^in followe-r srms 510 are rC'taisbly .-noujitc-d T3

the crankcase 110 and extend to rest upon the respective cams 360. The respect ve pusn rods 540 in turn rest upon the- respective cssa follower arms 510. As the cams 3£ ) rotate, the push rods 340 are temporarily forced outward away from the craakcass 11 * by the sam follower arms 510. This causes the rocker arms 350 to rock, or route, &ad consequently causes the respective valves 240 and 250 to opea toward the crania as© 110, As the cams continue to rotate, however, the push igds 34-0 are allowed by the cam follower arms 510 to return inward to their original positions. A pair of spr ngs 520 positioned between the cylinder head 170 and the rocker SOTS 350 provide fore tending to rock the rocker aims in directions tending to close the valves 240? 250, resj sctively. Further as a result of this forcing action of the springs 520 upon die rocker arms 350, the push rods 340 are forced back to their original positions,
[0029] Referring to Figs, 942, the carburetor 600 of the internal co nbustfcOB engine 100 is shewn. The carburetor has a body 610 that forms the rnahi sxmct zie of the carburetor 600. The body 610 has ,a. first end 632^ which sagagss and is tastes e4 to ths air filter 230, and a second ead 614, which engages and i$ fastened to the intake oil 200,
[O03S] Referring specifically to Figs, 11 sod 12, cross sectional vie^s of the osrteureca: 6-00 are 5to^T? tairsu alcr^g ib^ A-A and 3-B c-f Fig. 9. The carbm itor body 510 has 2ii integral nock 530 mat protrudes fern fete bottom of tfce bod]" 610 ar .-i extends downward therefrom- A fuel bowl 620 is fastened to the neck 530 by a bow nut 630. The fuel bowl 620 has walls 622 that define an interior volume 524 for coniz imng fiiel and extend upward to contact the bottom of the "body 610. A gasket 640 is located between the lower portion of the body 610 aad the fcel bowl 620 to prevent tl .© leakage. of fuel between lite fuel bowl 620 ma the body 610+
f0031] Referring specifically to Fig, 11, a cylindrical bore 650 is termed in one side of the carburetor body 610 and has a proximal sod at the outer sun face of the body 610 and extends generally horizontally into the body 610. The bore 650 -rausitions

apportically 90 degree in direcries between the promied and the disterend and such that the -distal end of the b-:=re 650: extens generally into me body 61 3 from fhe bottooi portion of the body 610 such that the distal md communcationswhich for-- fuel bowl interior volume 624.
[0032] An inlet adapter 780 is received within the proximal end f the bore 650 end is secured by means of a press fit The inlet adapter 780 hzten* 'O&ecta the

carburetor 600 and a fuel tank (not shown) and allows the Sew of fuel trcon lae u si IBXUL into the proxim&l end of the bore 650 through gravity feed or a fuel pump.
[0033] A fad control valve is disposed within the bore 650 and incl des an ialet seat 790 and pin S40. The inlet seat 790 is received within the distal end of i he bore 650 and is secured by means of a press fit. The Met seat 790 has a& integrally fanned side wall 800 and top wall 820. The side wall 800 is generally cylindrical £nd de lines an interior passage 310. The top wail 820 is integrally termed at one end of and perpendicular to the side wall 500 and includes a bots 830 therethrough which al ows the Sow of fuel from the bore 650 through the passage 810 through the inlet seat 790,
[0C34J Th.e pin &40 is received within the inlet seat 790 and has an fa.tegrally formed tip S70? body 880, (and md 890. The body 880 is received within the i ilet seut passage SiO and is shaped such that fuel can flow through the passage $10 an -uad the body 880. The Up 870 extends from the body 880 upward toward the valve seat cop wall 820 and is tapered such that the tip 870 seats against the bore 830 in the top wa il S20 to prevent the flow of fuel through the bore 830 when the pin 840 is In its uppermost position, as shewn in Figure 11, The end 890 extends from the body SSO opposi e the tip 870, protrudes outside of the inlet seat 790, and is coupled to a float 900, vfcich is discussed in more detail bdow, such that the position of tae pis 840 is control! :d by the movement of the float 900.
[0035] The float 900 is disposed within the fuel bowl interior voluan 624 aad is roiatably fastened to a pair of support aims 920 (only one showi\). which are i -legral to the carburetor body 610 and extend downward from the bottom of the body ',10, by a binge pin 960. The float 900 has a hollow body 310 that extends around the * acbaretor body neck 530 (see Figure 12) and floats upon the fuel in the fuel "bowl 520 sue h that foe float is raised wien the amount of fuel ia the feel bowl 620 increases aad i. lowered "3^53 the amoinit of fiiel in the &al bow! 620 dsoreases, The Soar 900 also h is an ans. 1*3-0;, integrally formed v=ith fh.e body 910, that has a lower protrusion 950 anc a pair of upper protmsions 940 (only oae shawa) that couple to the pin sad £90 such that the lo^ei and \3ppsr protrosioBs 950, 940 will rake and lower &e pis S40 as the aroi S 50 rotates
^00-^61 in. ODs-^.tiQTi. ^bj^ ^"^TH fb* "fes^ t^sli Soil's thr^ii^ii tk.f? in ft £d^Dter ^^0 into the bare 650. FIX?BI the bore 650 the fuel flows -t&OTagti the bora 83C in the top xvall 820 of the iobl ^es.t "90 and through. m& inlet se^i passage HI;^ noting .romid oio

nisi 840. ta the interior volume 624 of the fuel bow! 620. As the amouct of feel in ;h& fiiei bowl 620 increases ths float 900 rises. As the float 900 rises the arm 930 if rotated. clockwise (as shown in Figure 11) about the "hinge pin 950, This causes tfc-> lower protrusion. 950 of the float arm 930 to .push against the pin end S907 which mays; the pin 840 farther into the inlet sesi 790. When the amount of fuel in the fuel bowl 620 reaches a predetermined level the pin §40 is moved into its uppermost position (as s -own in Figure 11) which seats the pia tip 870 against the inlet soak bore 83O? thereby pr ventmg the flow of fuel through the inlet seat 790 into the fuel bowl 620. As the amour •; of fuel in the fad bowl 620 decreases the float 900 lowers. As the float 900 lowers the :aim 930 Is routed cou&terclockwise (as shown m. Figure 11) about the hinge pin 960. Th 3 causes the upper protrusions 940 of the float arm 930 to pull against the pis end 89 it which, moves the pin 840 further-out of-the inlet seat 790 an unseats the pin tip 870 (rom the inlet seat bore S305 thereby allowing flae flow of fuel through, the inlet seat 790.
[0037] Referring specifically to Fig. 12, an intake bore 700 is -ferns d in ihs Srst end 612 of the oarbtirefci body 610 2nd caimausicatos with the air Sites 230- A throttle bora 720 is fanned in fee second end 614 of the body 610 and communicate the the intake port 200, A veuturi 710 is formed ia the center of the body 610 hct -vaen the intake bore 700 and the throttle bore 720 and communicates with both the intake bore 700 and the throttle bore 720 such that air from the intake bore 700 passes into the verturi 710 . and from the veuturi 710 to the throttle bora 720.
[0038J A generally vertical bore 712 is fanned in the lower parti an of the body 610 and extends from a. proximal end at tie venom 710 downward throngh the neck 530 of the body 610 to a distal end The proximal ead of tfie bore 712 com annic&tes with the veataii 710 s^d tlie <&ta! ssd of the bcr;3 712 reedVe? the bowl nni 6 '10, wMch :c--a t>-«'V r. trie DO:L" ::U a^.a closes the cusiai aB^a .a: :a^ DOI.^ /lz. A fael jet 770 Is rscebed -wtfeiri s- bore^ 1^ ~ie n^cfc 530 ad allots fe fb^r of me; fesi tb.e fuel ho^vi mterior voiuaiie 624 to ths bore 712. A -^azsle 730 i3 received v;7.thi t :hs "bore 712 and communicates fiiel that is received info the bora 712 to the verstuii ' 10 dariag Bcs-idle operation of the ssgine. Altensatively, rather than having a separate |st nozzle 735 -ffiitbbi ::he bora 712, th© bore 712 could be shaped to periom the fesc* .oa of thr rioszle 730 and the nozzle 730 could be rssnoved An idle tube 740 has & p& simsi ead that is seoured ^ithiii a hole 660 formed at the upper portion ox" the bad;- oi 0 £ id extends downward through the venturl 710 into fee n$zzl& 730 and tannisates st a distal end
w1

within the nozzle 730. If a noszle 730 Is not usei as described above, the idle tube 740 would extend downward Into the bore 712 and terminate at die distal end withii the bore 712. The hole 660 is closed above the proximal end of the idle-tube 740 by t press fit *tssl ball 610, or othsr mesus for closing1 the hole. The idle tubs transfers met from the bore 712 to the throttle bore 720 dqnag idle operation of the engine.
[0039{ A throttle, plate 750 is rotatably mounted within the throttle >ore 720 and is connected to a tkrottte control 760, which controls the orientation of th s throttle plats 750. Hie orientation of the throttle plate 750 controls the amount of fael/ai ■■ mixture ihat passes through Iks throttle bore 750 into tte intake port 200, &s is describe* i In. more detail below.
[0040] In operation, air flows through the air filter 230 into the in atee bore 700 and from the intake bore 700 to the ventori 710, In the ventuii 710 the pi assure of the air is reduced which creates a vacuutn within, the nozzle 730. The vacuum : ;>nned hi the nozzle 730 pulls facl from the fuel facwl 620 through, the ihd ]ot 770 and ird* &e bore 712 in the neck '530 of the carburetor body 610. The fusl m the bore 712 navv, tMouuh the noszle 730 and into the venfeui 710 Yvtssre it raises ^aih the air to produce 11 air/fael xablure. Tat air/flid rrixture irom the veaturi 710 thsa flows to th.e throttle bar 720 and from ths ibrottio bore 720 into the Intake port 200. The throttle plate 750 rota" -33 withis tbs thioti'fe bore ^20 to oantrol the flow cf tfee fiiai/dr mixture fom ike throttle bare 720 to the intake port 200,
[0041] Referring again to Figure 11, a geaerally horizontal bore 702 .s formed in the caxbur&tor body 610 and extends from the intaks bore 700 (see Figure 1C 1 into the body 610, such that the bore 702 communicates with fee intake bore 700, A generally v^iticU hoie (not shown) is founded thebody 610 andextoads &om the k>iintal bore 702 through the bottom of the body 6IG, such thst the vertical bore communicateales *Ai± both the hori^ostal bore 702 and the fowl bowl fetemal lunie 624-. Ths hoiiz^ ntal bor^ 702 ffid the verdcal bore define a bowi vsnij which imsreomiects the intake bor ■ 700 10A *ii& iitsrior Yaiame 624 to squsiiee the presse wixhia the ioterior ?olum ? 524 by -.i.-\iu--i iviz fevim "i.,' filter'"r iz"ji :I" fe &f intslrv ro-6 700 s the- snioi il '>i"fb6'. iu ~iie iHienor shiiuw o24 uiors^sd^ £IKI ■jrov^diiig tpr rroni t!i- intiJrC DOIS; '. i0 to th.t inxerior volums 624 as the amount of fad in &$ interior voiame: 624 dscreeses.
[0042] Iii addition, a fuel sorictiraent system, is shown that provides I ;ie correct fiiel enrichment durmg start-up cranking without operator interventioi thereb; avniding

lie problems of over or under enrichment The fuel enrichment system has a pas :age that has an mist 680 thai conumiiiicaies mm the horizontal bars 702 of die bowl vei i and 3D. outlet 690 that communicates with the nozzle 730. Alternatively, the inlet 61) of the passage could also communicate directly with the intake bore 700 or connect to t e intake bore 700 in some other roanner, as long as air is allowed to pass into the passage iom the intake bore 700 and from the intake bore 700 into the passage. la addition, the c itlet 690 of the passage could also communicate directly with the bore 712 in the body 11 a nozzle 730 is not used) as described above* ar directly with the vealaii 710.
£0043} la the preferred embodiment, the passage of the xuel srdchment systsia is forined by a generally vertical cylindrical bore 370 and & generally I >rizontai ■ bore 380. The generally vertical cyiiadric&i bore 370 fotnae-d in the caiburstor ody 610 mat extends &om a proxoxi&L end at the inlst 6S0 of the passage to a distal eid at the bottom of the carburetor body 610, such &kt the vertical bore 370 communicate;. with the horizontal bore 702 of the bowl vent The generally horizontal bore 380 is alt > formed through the side of the carburetor body 610, opposite the bore 650 that receive; the inlet adapter 780. The horizontal bore 380 is generally perpendicular to sxid inte sects the vertical bore 370 sad extends from a oroximal sad at flte outer surface of the ( arburetor "body 610 to it distal end at the- outlet 690 of the passage, such that the distal * ad of the bore 380 commumcatss "with the nozzle 730 rod air from the vertical bore 37C can "flow through the horizontal bore 380 and into the nozzle 730. The proxiuxal end o ;* tha bore 380 Is sealed bv a Dress fit siod ball 390, or other moms for sealing the bo e 380. to prevsrit the Jeak&ge of dk from the b-ynzczkA bore 380 to the alxaosphere.
[00441 A valve seat 460 is rsosiv&i within the distal §nd cftlie ve teal bore 370 and is secured via a press fit ot other securing meacs. The valve s-. at 460 is cylindrical and extends &cill h-t- abb te cG-izninmcate with tis& horizontai bore 3 :0 in. the
carburetor bodj^ 610. Aitenxatiyefy, if alignment of the valve seat 460 is not a a acerii, a
single horizontal bore 480 in the valve seat 460 could be used. The vertical bore 470 and
horizontal bores 480, 490 form the passage through the valve seat 460 that a' ows air
from the vertical bore 370 in the carburetor body 610 to flow to the horizontal bo a 3S0 in
ths carburetor body 610.
[G046] A ball 400 h disposed witfaift &s verii&al bore 370 at the dist I end cf the valve seat 460. The diameter of the ball 400 is slightly smaller thaa the die ueter of the verticsl bore 370- suck thai: air is allowd to flow aroirad the bail 400. Wber the bail 400 is ar its kwsnnost position, as sii^w^ vx Figure H. f:ie bsll seats against ■ \e distal -rid oz -.be ""LJ^^ >;e,jj.t -60 pr6"e^ii:if the fie*"" of air from the bsts 370 ir^o xh< vertical hCjTt 470 in the valve seat 460'. As die ball 400 is raised from its lowermost po itiot-j as described in more detail "below, air is allowed to flov' groimd the ball 400 anc into tbe vertical bore 470 is. the valve ssat 460-
[0047] The mass of the bail 400 should be so.ch that lie ball will remt a seated against th.s distal md tf fe i^aive seat 460 "wiien the s^g^ Is at or belov; stsrt-up craiudag speed (stert-up crasddng speeds are typically 500 rpm but may vary d peadmg

on the engine). In addition, the bail 400 should hays a natural frequency such th* I it will not resonate within the vertical bare 370 and unseat ikm. the distal snd of the vs ye seat 460 due to the vibrations produced by the engine at or below start-up cranfcraj speed. However, the natural firequ^acy of fee ball 400 should be such that between engi ie startup oiarldiig speed and the marimimi speed of the engine, the vibrations produce ■ by the engine will cause the- bail 400 to resonate v/ithixx the bore 370 and unseat torn t .e distal end of the valve seat 46G, which will allow air to flow aroirad the ball 400 and into the vertical bore 470 in the valve'seat 460,
[004S| At normal engine miming speeds, the vibrations produced by the engine will cause the bail 400 to resonate with the "bore 370 dua to the natural ft squency of the bail 400. This causes the ball 400 to uaseat from the distal end of the v. Ive seat 460, which allows air from the bore 702 to flow through the vertical bore 370- ar und the bail 400, and into the vertical bore 470 in the valve seat 460. This air then flows through. the vertical bore 470 and horizouM bores 430, 490 in the valve scat 460, into he bore 3 SO itttho carburetor body 610, and into the nozzle 730. The air from the nozzle r30thsn flows to the v&niisri 710 where it safces vdxh the air &om the intake bore 700 sue the fuel 3-om the aozsle 730, n discussed above, Tb.e &ir Sront the intake bora 700 and tb ; £ir that passes througb. the enrichment system cambine to provide the correct inel/air mi. Time fox proper engine perfoiinance and emissions.
[004S] Conversely, during engine sturiap, the weight of the bail 4(M a&d the low ipra of the engme, and therefore low vibratioa of the engine, keep the bail 4- 0 seated against the distal end of the valve saat 460 thereby preyentiig air from, flowing from the bore 702 through the bores in the valve seat 460 and to the nozzle 730. Therefoi s3 daring startup, a portion of tfce air that would normally flow into the venturi 710 xom the enrichoiem system, is ranoved sud only the sir fern the i&tate bore 700 3c v to the vsaniri 7ID. This d6crea$cs me ;^K3\ZIU: C;-£ sir in. the faey'air inlxtare. which m :cbes th.e iuelfe imxture at start-up tbsr^by impro-ving engiiie starting o^p&bilic^ Th ; systsi]i provides the correct fuel enriciunent ^faring attgina start-up cranking wiihon^ operator inierreutton snd allots adjustmeat to prevent ov©r or "ander minchm&ti£. The, fael
:*oi ?-' iea^^ E. >ow idi? g>S5;ij3 7-^jIoh ^"->ii.id iudfeats that 3ie ^@"^- I?3d ^ucces" Jll;i" "b~?n started sad craiMiig cf ths engine cauld be eadsd.

[ODSO] Is the present embodiment, the engine 100 is a vertical si aft engine capable of outputtiag 15-20 horsepower tor implementation in a variety of com .naer lawn and garden machinery such as lawn mowers, In alternate embodiments, the * exgine 100 can also be implemented as a horizontal shaft engiixe} be designed to output greater or lesser amounts of power, and/or be implemented in a variety of other types of machines, e.g., snow-hfowsrs. Further, la alternate embodiments, the particular airac jement of parts within the engine 100 can vary from those shown and discussed at we. For example, in one alternate embodiment, the cams 360 could be located above the gears 320 rather than rademeaih the gears.
[0051] While the foregoing specification illustrates and describes &< preferred iinbodnnsjate of this iaventioii, it is to be understood that the invention is not limited to the precise oon^mictiaa herein disclosed The invention can be embodies ra other specific forms without departing from the spirit or essential attributes of the nveutioiL Accordingly, reference should be made to the following claims, rather tl m to the foregoing specification, as indicating the scope of the invention.

CLAIMS
What is claimed is:
I. A carburetor for an internal combustion engine, comprising:
a body having a first end that fastens to an air filter, a seconc end that fastens to an intake port of a cylinder head, an intake bore famed in the first end, a throttle bore formed in the second end, a vsnturi formed between the it take bore arid tie throttle bore that intercoimects the intake bore and throttle bore and a jet • passageway extending from the venlari through the body for providing; id to the venturi;
a fuel bowl, having walls thai; define an interior volume, feste, d to the body;
a fuel enrichment system, responsive to the vibration, of the eugii x having a passage fanned in the body that 'has an inlet that communicates with be intake bore and an outlet that communicates with, the jet passageway, where! the fiiel enrichment system reduces .the flow of air through the passage when the engine is at speeds less than idle speed and increases the flow of air through the passage when the engine is at speeds greater than crardcmg speed.
2. A cacbaretor for an internal combustion engine, as recited in claim 1,
comprising a jet nozzle; disposed with in the jet passageway where in the out at of the
passage of the fuel enrichment system connnunicates with the jet nozzle.
3. A carburetor for an interal conxbustion engine, 35 recited in claim 1,
comprising a bowI vout, fomed in the body,, icterconnecting the irtake bon and the
interior volume of the fuel bowl, wherein the inlet of the passage of the foci s) dchiment
system oommunications with the bowl vent
4 A carburetor for an internal combustion angine, as recited in claim 3, comprising a jet nozzle disposed within the jet passageway, wherein ths out 5t of the
passange of the- fuel environment system communicates with the jet nozzle.

5. A carburetor for an internal combustion, engine, as recited in claur ; I, 2, 3, or 4, wherein the fuel enrichment system comprises:
a valve seat, disposed within the passage in the body, the valve se; : having a passage to- allow the flow of air through the valve seat; and
a ball disposed within the passage in the body, wherein the t ill seats against the valve seat blocking the passage ia the valve seat when the en; ine is at speeds less than cranking speed and unseats from the valve seat and vibrates within the passage in the body thereby unblocking the passage in the v lve seat and allowmg air to flow through, the passage in the valve seat when the ngine is at speeds greater fhasreranting speed,
S. A carburetor for an internal combustion engine, as recited in :claim 55
therein:
the passage in the body Is formed by a generally vertical bor , which extends from a proximal end st the inlet of the passage of the fusl en ichment system through the body to a distal end that communicates with the internal volume of the fuel bowl and a generally horizontal bore, which extend . from a proximal end at the generally vertical bore to a distal end at the outl t of the passage of the fuel enrichment system;
the valve seat is press fit into the distal end of the generally verti al bore: and
the passage in the valve seal: allows the flow of air from the vertic; I bore to the horizontal "bore.
7. A carburetor for an internal combustioa engine, -as recited in claim 5.,
a generally vertical bore that communnicates with the generally vertical bore of the passage and extends into the valve seat; and
a generally horizontal bora feat extends fom the generally vertica l bore in the valve seat to the generally horizontal bore of the passage.
where in. the passsge through the valve seat further comprise, &. second generally horizontal bora, perpendicular to the hoxizontal bore, that sxtsuds ftoo in the generally ■ vertical bore in the valve seat to the generally horizontal bore of the passage.

9, An internall combustion engine having a. carburetor that I fastened between. an air fliter and an intake port of a oylinder head, the carburetor comprisinga body having a first and that fastens to the air filter, a secor t cna that fastens to the intake port, an. intake bore fanned la the first end, a tfc ottle bore formed in the second end a venturi formed between the intake bo a and the throttle bore that interconnects the intake bore and throttle bore, and a jet passageway extending from the veaturi through the h.ody for providing 5iel to the veuturi;
a fuel bowl, having walls that define aninteriorvolume, faste led to the
-* -f
a fuel enri.chmnent system, responsive to the vibration of the engi ne, havinga passage fboncd in &e body that has an inlet that conuniixacates-witib. Ihe. intake bore and an outlet that commuuicates with the jet passageway, where the fuel enrichment system reduces the flow of air through the passage when ib eagine is at speeds less than -cranking speed and increases the flaw of air through the passage when lie engine is at; speeds greater than cranking speed.
10- An internal combustioa engine, as recited in claim 9, compr ing a jet nozzle disposed within the jet passageway, wherein the outlet of the passage f the feel
11. An internal combustioa engine, as recited in claim 9, comprisin g a bowl
vent, fbuned in the body, intercotmecing th.e intake bore and the interior voli ne of the
fuel bowl where in the inlet of the passage of the foe! enrichmentsystem com oonioatis
wilt the bowl vent
12. ALL INTERAL c;GtEibnsdoii -srigiaBj as reoitsd claim. II, oompr ising a jet
nczrfe disposed wuhin die jet pssage way, whsreia trie outlet of the passage f the foei
enrichnieiit system coiriiiiimicates with ftie jet nozzle.

13. An internal combustion engine, &s recited m claims 9,,10, 11 or 12,
wherein the fuel enrichment system comprises:
a valve seat disposed within the passage in the "body, 'the valve set having a passage to allow the flow of air through the valve seat; and
a ball -disposed within the passage in the body, wherein the b 1! seats against the valve seat blocking the passage in the valve seat when the eo| :ne is at speeds less than cranking speed and unseats from the valve seat and vibrates within the passage in the body thereby unblocking the passage in the v. Ive seat and allowing air to flow through the passage in the valve seat when the t igins is at speeds greater than cranking speed
14. An internal combustion engine, as recited in claim 13, wherein:
the passage in the body is foxnisd by a generally vertical bor , which. extends from a prornn&I m& at the inlet of the passage of the fuel sn ichixient
system through ins body to a distal ©nd that commmdeates with the internal volume of the fuel bow\ and a generally horizontal bore, which extend 5rom a proximai end at ths generally vertical bore to a distal end at the outl I of &e passage of the fuel smiciiirL'Mt system;
the valve seat is press fit into the distal end of the generally verti al bore; and
the passage in the valve seat allows the flow of air from the veiticl : bore to the horizontal bore.
15. An internal combustioa engine, as recited in claim 14, whereinthe passage
though the valve seat comprises:
a generally vertical bore that communicates with the generally vertical bore of the passage and extends into valve sest; and
a g^sraily Iiorizonxal bore tlist extends from the geaeraily vertici :. bore in the valve seat to the generallv horizontal bore of the passage.
16. An interal communicates engine, as recited in claim15,.wherein. the passage
to the horizotitai bore, that extends fom the generally vertical bore in the valve seat to the generally horizontal bore of ths passage.
17. A carburetor for an internal combustion eagine? comprising:

a throat having a bore that extends through, it from a first end £ to which combustion air is drawn to a second end through which an air/fuel mi* ure exits the- throat;
a fad. bowl having walls that defiue an Interior volume:
a jet passageway from the interior volume of the feel bawl fuel il 3 bore of the tbroat to provide a Sow of fiiesl irom the interior volums of the feel b -wl to the bore of the throat to mix with the flow of air through the bore;
a fuel snrichmeat system m commumcatkm with &e bore of the iroat? the fuel epriclimeut system having an air passageway that supplies a flow o: air to the jst passageway at engine speeds above a start-up cranking speed of the e tgine, the device being reapojjsivc to yibrstiou of the engine at normal engine operating speeds to reduce the flow of air through the air passageway to ths jet p; ssageway above the start-up cranking speed of the eugine,
18. A carburetor for an mtsznal combustion sa.gine, as xeoited in riaini 17,
wberein the ait passageway of the fa:el sDrisbneiit device opens in the jst passat sway.
19. A carbixretor for an Intemal cctribxistiaxi engine £B rscite in daim i.7t
■y^iiereiB the fqel sniicfanent device fes an element that opens an ait valve to ii ;rease the
flow ox air through the air passageway ta. response to vibration of the engine at normal
engine operating speeds above the start-up cranking speed of the engine.
20. A carburetor for an internal combustion sagiae,, as recited in claim 1%
wherein the element is a ball, and the bail vibrates at noxmal engine operat ig speeds
above the start-up cranldng speed of the engine to open the aix valve.