Carburetor needle valve adjustment limiter cap apparatus and method of adjusting fuel flow

In a carburetor having a valve for adjusting fuel flow by rotating a shank of said valve by engaging a head end of said valve shank projecting from the carburetor, a limiter cap of the type having a body with a passage therein constructed and arranged to be telescopically received over said head end of said shank, detent means for axially retaining said cap on said shank comprising a recess in one of said head end of said shank and said body passage, a projection on the other one of said shank head and said body passage, at least one of said recess and said projection being substantially circumferentially continuous, said recess and projection being constructed and arranged so that when said body is telescoped over said shank in a first position said projection is received in said recess so that said shank can be rotated relative to said body while said body is axially retained on said shank, said body having a valve rotating engagement portion in said cap body passage constructed and arranged to rotationally drivingly engage with said shank when said body is received on the shank in a second position axially spaced from the first position to thereby couple said body to said shank for rotation only in unison therewith, an arm fixed to said body and projecting generally radially thereof and constructed and arranged to limit the extent of rotation of said body to less than one complete revolution at least when said body is in either of the first and second positions by engagement of said arm with at least one stop carried by the carburetor and projecting into the arcuate path of rotary movement of said arm, whereby when said body is telescoped over said shank and is axially disposed in the first position said shank can rotate relative to the body while axially retained thereon and when said body is in the second position said shank and said body can be rotated only in unison to less than one complete revolution to thereby limit adjustment of the valve;

• the improvement in combination therewith wherein said detent means of said body is formed by a resiliently flexible portion of a retainer clip made of spring material and secured axially in said cap body.

In a method of adjusting the fuel flow of a carburetor and limiting further adjustment thereof of the type involving the steps of:

• (a) providing a carburetor having at least one valve for adjusting fuel flow by rotating a shank of the valve projecting from the carburetor, the valve shank having a rotator end head and a stop shoulder spaced axially therefrom with a first recess between the shank head and stop shoulder and a second recess adjacent a side of the stop shoulder remote from the shank head,
• (b) providing a limiter cap having a body with a passage therein opening at one end and constructed and arranged to be telescopically received open end first over the head end of the one valve shank for retention of the body in a first position on the one valve shank with the body being freely rotatable relative to such shank, and shank engagement means in the body passage and constructed and arranged to rotatably drivingingly engage with the cap engagement means on the one valve shank when the cap body is telescoped thereover and in a second position axially spaced from the first position to couple the one valve shank with the body for rotation only in unison therewith,
• (c) providing a limiter arm fixed to the body and projecting generally radially therefrom and constructed and arranged to limit the extent of rotation of the one valve shank to less than one revolution due to engagement of the arm with at least one stop carried by the carburetor when the body is in the second position,
• (d) providing a spring material retainer clip constructed and arranged to be telescopically received within the cap body passage and having resiliently flexible internal and external detents,
• (e) telescopically assembling the retainer clip into the open end of the body passage to an installed position such that the external detent retains the clip and body against axial relative motion therebetween,
• (f) then mounting the cap on the one valve shank with the body telescoped over the shank and in the first position thereof on the shank by sliding the body and clip open end first to cause the shank head to flex the clip internal detent until the clip internal detent is moved axially past the shank head and then springs into the first shank recess with an audible click to signify cap retrograde axial retention of the cap on the shank in the first position,
• (g) mounting the carburetor on an engine with which it will be utilized,
• (h) thereafter while operating the engine and with the cap in the first position on the one valve shank making any further needed adjustment of the one valve by rotating its shank to fine tune fuel flow to optimize predetermined operating parameters of the engine, and
• (i) after step (h) moving the cap body to the second position on the one valve shank by sliding the body and clip so as to flex the clip internal detent by moving it over the shank stop shoulder and then spring into the second shank recess with an audible click to signify cap retrograde axial retention of the cap on the shank in the second position while concurrently causing interengagement coupling of the shank and cap engagement means to thereby limit any subsequent adjustment of the valve due to the arm of the cap bearing on at least one stop carried by the carburetor and disposed in the arcuate path of movement of the arm at least while the cap is in the second position on the one valve shank.

A limiter cap adapted for end-user-non-removable installation in surrounding relation over the adjustment head of a rotationally adjustable fuel flow control valve of a carburetor having a shank joined to the valve head, said cap comprising a tubular body having a hollow interior and being open at least at one axial end, and a retainer clip end-user-non-removably carried within said body interior and defining therewith a hollow interior passageway open at least at one axial end closest to said body open end, said body and clip passageway being constructed and arranged to telescopically receive the valve head and a portion of the valve shank therein with a close sliding clearance fit between the valve head and passageway and such that the valve head is covered by said cap in a fully installed position of said cap on the valve shank, said clip having a resilient detent member yieldably protruding inwardly into said passageway adapted for detent engagement with a first locking portion of the valve shank that is spaced axially inwardly therealong from the free end of the valve head to thereby prevent retrograde telescopic end-user removal of the cap from the fully installed position thereof on the valve head, said cap having shank engagement means constructed and arranged for co-rotational driving telescopic engagement with the valve shank in the fully installed position of the cap on the valve shank, said cap also having rotation limiter means cooperable with stop means operably connected to the carburetor for limiting cap rotation to less than one revolution in the fully installed position thereof.

A limiter cap holder clip for use with a carburetor having first and second jets and first and second side-by-side adjusting valve screws respectively operable in the carburetor for fuel flow control of the first and second jets, each screw having an adjusting head extending from the carburetor in exposed condition for jet adjustment, and for further use with first and second open-ended limiter caps each having a rotational limiting means and being respectively individually telescopically receivable open-end first on the screw adjusting heads in laterally closely spaced side-by-side paired relation, said holder clip being made of semi-resilient, non-elastic material resistant to damage by ozone and petroleum products and having first and second opposed end lobe portions respectively constructed and arranged for partially encircling and engaging the first and second caps, said holder clip further having bight nip portions connected to said lobe portions and generally spanning the space between said end lobe portions, said holder clip lobe portions having cap interengaging means constructed and arranged such that said holder clip lobe portions are adapted to hold the caps in laterally spaced parallel axis relationship, to orient the caps for telescopic open-end-first assembly onto the screw heads and to yieldably resist rotation of the caps about their axes relative to said holder clip.