Automatic enrichment device, to overhaul—Operation N/ Q-20A

          
Workshop hand tools:
Spanner sizes: 0.81 in. A F open ended
Screwdriver, small; Phillips screwdriver, medium
Flexible 6 in. rule
Thermometer
Special tools:
Checking tool for float level, Part No. 606000
Alignment tool for valve body and jet tube bore and setting screwdriver, Part No. 605998
Setting probe for main valve and needle lift, Part No. 606001

IMPORTANT
The automatic enrichment device is a precision instrument and should be treated as such. This applies particularly to the bi-metal assemblies, which must not be distorted or bent in any way.
High standards of cleanliness are required when working on the Automatic enrichment device. Petrol or paraffin may be used to clean components. Use nylon cloth, never material that is fluffy or that leaves lint, when drying any components.

 		     
     
Automatic enrichment device, to dismantle
1. Remove the polypropylene heat insulation cover from the unit, then use penknife or thin bladed screwdriver to prise out the three aluminium blanking plugs in the top cover.
2. Hold unit upright, taking great care to avoid damage. Unscrew the two long screws retaining the moulded bakelite top cover and remove the cover carefully, separating from gasket if necessary. Remove adjustment grub screws if replacement is necessary.3. Carefully lift the main bi-metal complete out of the V slots and disengage from the top of the valve stem by sliding back over the V slots. Remove the locating washer from the top of the valve stem. Unscrew the jet needle complete and withdraw from body. Remove top cover gasket.4. Unscrew the two screws retaining the moulded bakelite valve body and remove the body. If the body is stuck to the lower body gasket, separate by tapping the side of the valve body with the handle of a screwdriver.
     
           
Top cover and main bi-metal
A—Valve body
B—Gasket for top cover
C—Jet needle complete
D—Top cover
E—Hollow grub screw, adjusting needle
F—Aluminium blanking plugs
G—Grub screw, adjusting valve
H—Valve stem
J—Locating washer for main bi-metal complete
K—Main bi-metal complete
L—Loading spring for main bi-metal complete
M-Screw and washer fixing top cover
N-Heat insulation cover 		          Valve body, diaphragm, float chamber lid and float
A—Main body
B—Gasket for valve body and float chamber lid
C—Float
D—Float chamber lid
E—Screw and washer fixing float chamber lid
F—Nylon filter
G—Plug and washer retaining nylon filter
H—Valve body
J—Special plain washer fixing valve body
K—Screw and spring washer fixing valve body
L—Jet tube
M—Air entry valve, spindle and spring
N-Clamp ring for diaphragm
P-Main valve and diaphragm		  
                                                     

5. Depress main valve then ease the pressed steel diaphragm clamp ring out of the valve body taking care not to damage the moulded rubber diaphragm surrounding the main valve head. Remove the main valve assembly, complete with diaphragm, from the valve body. Lift the lower body gasket in order to remove the air entry flap valve, together with spindle and spring.
6. Unscrew the large screw plug and remove the filter.
7. Unscrew the three screws retaining the float chamber lid and remove the lid carefully. If it is stuck to the main body, separate by tapping the side of the lid with the handle of a screwdriver. Remove the float needle and float assembly complete with hinge pin. The float needle may now be detached from the float by unhooking the wire stirrup. Remove the lower body gasket.
8. Take the main body and noting that the brass jet tube protrudes above the face of the casting, place the body upside down on a piece of wood having a hole drilled to accommodate the protruding jet tube. It is important that no load is applied to the top of the jet tube at any time, otherwise the jet location may be altered.
9. Unscrew the four screws retaining the needle diaphragm cap and hold the cap against the load of the spring inside it whilst withdrawing the screws. If the cap is stuck to the diaphragm, hold the unit firmly then separate by tapping smartly at the side with the handle of a screwdriver. Remove the cap, spring, diaphragm and hollow locating dowel from the main body.
10. Unscrew the screw retaining the air entry pipe clamp and remove air entry pipe and clamp.

 
                    Diaphragm cap, diaphragm and air entry pipe
A—Wooden block with drilled hole to accommodate brass jet tube
B—Body casting
C—Diaphragm
D—Spring for diaphragm
E—Diaphragm cap
F—Screw and washer fixing diaphragm cap
G—Hollow locating dowel
H—Air entry pipe
J—Clamp retaining air entry pipe
K—Screw fixing clamp
   
               

Inspection
11. (a) Wash all the components using clean petrol
(b) Ensure that all drilled holes in the main body are free from obstructions.
(c) Examine the valve body and ensure that all holes are clear.
(d) Check that the valves stem articulates freely in the valve head and the two air bleed holes in the head are clear.
(e) Check that the rubber diaphragm has not been damaged.
(f) Examine the needle assembly and check for free movement in adjuster screw and straightness of shaft
(g) Check that the bi-metal assembly in the top cover moves freely on its mounting screw. Do not remove bi-metal from cover.
(h) Check that all pipes and drillings in the float chamber lid are clear and that the filter is clean.
(j) Examine float needle tip for wear or damage, also seating in float chamber lid.
(k) Ensure that the float assembly pivots freely in the float chamber with clearance all round and that there is side play of the float spindle in the body recesses.
               
        Diaphragm replacement
A—Screw and washer fixing diaphragm cap
B—Cap for diaphragm
C—Spring for diaphragm
D- Diaphragm
E-Hollow dowel locating diaphragm and cap
                                   
               
Automatic enrichment device, to re-assemble
1. Place the main body upside down on a piece of wood with a hole for the protuding jet tube.
2. Ensure that the hollow dowel is free from obstruction then fit to main body. Place diaphragm over dowel, with flat rivet head downwards and align with screw holes. Position spring in locating plate of diaphragm. Place cap over spring and press down taking care to engage with the hollow dowel and to keep the screw holes aligned. Whilst holding the cap down against the pressure of the springs check that the diaphragm has not puckered around the edges of screw holes.
Fit four screws with spring washers and tighten evenly.
           

Checking float level
A—Float chamber lid
B—Checking tool, Part No. 606000
C—Stirrup for needle
D—Float
E—Unner cAtting limit
F-Lower setting limit
G-Setting limit indication

    
3. Check float level as follows:
(a) Invert float chamber lid.
(b) Locate float needle and float to lid, using checking tool for float lid, Part No. 606000 as illustrated.
(c) Check the float level as illustrated, float should rest lightly on the needle.
(d) If the float is outside the limits, adjust by setting tongue on float lever.
(e) Remove special tool together with float and float needle.
4. Hold unit correct way up.
5. Position lower body gasket on top face of body and locate with two screws opposite to the float chamber.
 
     
Float replacement in lid
A—Float held against face of lid with steel rule or feeler gauge
B—Stirrup on float needle
C—Float
D—Float needle
E—Float chamber lid		      
6. Drop needle into seating of inverted float chamber lid. Then ensure float needle is correctly located on float lever by wire stirrup. Holding float assembly to face of lid with the tip of steel rule or feeler gauge. Position the lid over the float chamber close enough to allow the float assembly to be dropped, so that the hinge pin falls into the recesses in the body without disengaging the needle from the seating bore.
Lower the lid on to the main body, align screw holes, fit three screws and spring washers and tighten. Test that the float is moving freely in the chamber by rotating the whole unit around the float hinge pin axis and listen for the movement of the float. Remove the two screws used to locate the gasket.
7. Replace the filter in the float chamber lid using new aluminium washer, refit plug and tighten.
8. Fit the main valve assembly to the valve body and ensure that the stem moves freely in the bush.
           
       

Float replacement in body
A—Gasket
B—Locating screws for gasket
C—Float chamber lid
D—Nylon filter
E—Plug and washer retaining nylon filter
F—Screw and washer fixing float chamber lid
G—Float
H—Ensure hinge pin falls into recesses of body
           
9. Assemble the air entry flap valve with spring and spindle. Turn back gasket to allow air entry valve to be fitted with spring in loaded position. Replace gasket and ensure that its edges do not foul the air entry valve.
Place steel rule along main body to cover valve seating and hold air entry valve in place. Position diaphragm clamp ring directly over the main valve seat on the steel rule.

Pick up valve body by top of valve stem and position carefully over the main body so that the clamp ring engages in the diaphragm recess.
     
 
Main valve replacement
A—Valve body
B—Main valve and diaphragm

Air entry flap valve replacement
A—Spring in loaded position
B—Spindle
C- Air entry flap valve
D-Gasket turned back to allow valve to be fitted

 		Preparation for valve body replacement
A—Steel rule in position over main body
B—Valve body
C—Screw and washer fixing valve body
D—Special plain washer fixing valve body
E-Air entry flap valve
F-Diaphragm clamp ring
Align the screw holes, fit two short screws with spring washers and fixing tags and lightly tighten. Remove steel rule, It is important that the threaded insert in the valve body is aligned with the jet tube bore. This should be carefully done by the use of an alignment bar, Part No. 605999. This is a metal bar having two diameters; the smaller, 0.185 in. (4,7 mm) dia being not more than 0.75 in. (19 mm) long, and the larger, 0.218 in. (5,55 mm) dia, being not less than 1 in. (25 mm) long.
             

Checking valve body and jet tube alignment
A—Valve body
B—Screw and washer fixing valve body
C—Alignment bar for valve body and jet tube, Part No. 605999

 		Checking operation of air entry flap valve
A—Air entry flap valve
B—Pencil		   Jet needle replacement
A—Circlip
B-Adjuster screw for jet needle
C-Valve stem
D-Jet needle
                                                   

The small diameter end is fitted into the jet tube and the valve body adjusted so that the larger diameter can pass through the insert to abut against the top of the jet tube. The retaining screws can then be tightened and the alignment bar withdrawn. Check that air entry valve operates freely, by carefully lifting the value against the spring with a pencil through the air entry hole.

10. Drop the Jet needle complete into the jet tube and screw the square headed adjuster screw into the valve body about three complete turns.

An approximately correct mixture setting can be obtained by the following method:—
Press the top of the jet needle down as arrowed so that the top circlip is firmly against the top of the adjusting screw and proceed to screw the adjuster down. As soon as the jet needle can be felt to have seated in the jet (recognised when adjuster leaves the circlip behind) screw the adjuster up until it can be seen to have abutted against the circlip. Release the pressure off the top of the jet needle. Now note the position of the needle adjuster and then turn it anti-clockwise three flats (3/4 turn).

11. Position the top cover gasket on the main body. Fit the locating washer to the ball top of the valve stem. Take the bi-metal complete and engage the spring clip with the locating washer on the valve stem. Position the ears of the bi-metal heat shroud in the V slots of the valve body.
12. It should be noted before fitting the top cover that there are serrations moulded into the top cover to hold the needle adjusting screw in position. These serrations allow twelve positions of the adjuster in one complete turn.

Before fitting the top cover therefore, the needle adjuster should be positioned to the nearest setting to line up with the serrations in the top cover cap.
                                                   
   
Main bi-metal complete replacement
A—Main bi-metal complete
B—Spring clip
C—Valve stem and locating washer correctly assembled
D—Locating washer on valve stem
E—Valve stem
F—V’ slots in valve body
G—Gasket on main body		   Top cover replacement, Stage 1
A—Serrations in top cover
B—Loading spring for main bi-metal complete
 

Note: Bi-metal fork must be below the washer as illustrated at C.

  
                                               
13. Ensure main bi-metal loading spring is located in position in the top cover then place the top cover squarely in position over the valve body taking care not to disturb the jet needle setting. Press the cover down firmly against the load of the main bi-metal loading spring and hold in position.
Fit two long screws with spring washers and tighten.
14. Fit air inlet pipe as illustrated then secure with clamp and screws.
15. Adjust main valve and jet needle lift. Operation N/Q 22A.
                                       
Top cover replacement, Stage II and air inlet pipe
A—Screw and washer fixing top cover
B—Top cover
C—Air inlet pipe correctly positioned
D—Clamp and fixing screw for air inlet pipe