Main valve and jet needle lift, to set—Operation N/Q-22A

        
                               
 
Workshop hand tools:
Screwdriver, small
Special tools:
Setting screwdriver and the alignment tool, Part No. 605999;
Setting probe for main valve and needle lift, Part No. 606001; Thermometer

NOTE: If the setting operation is to be done with the Unit installed it is of paramount importance to ensure that the engine is at ambient room temperature before any adjustment is attempted. Failure to observe this rule will give incorrect setting.

Main valve and jet needle lift, to set
1. If unit is being set after overhaul, hold securely in upright position.
2. Remove polypropylene heat insulation cover from the unit and prise out the three aluminium blanking plugs using penknife or thin bladed screwdriver.

    
                               
      Heat insulation cover removal
A—Heat insulation cover
B-Aluminium blanking plugs
C—Hollow grub screw position, jet needle lift adjustment
D—Grub screw position adjacent to probe hole, main valve adjustment
E—Probe hole, centre of top cover		      
                               
  3. To measure jet needle lift insert probe through hollow grub screw. With knurled portion held firmly on top cover and sliding member of probe abutting the knurled portion, press probe down firmly to stop and release. Continue to hold knurled portion of probe firmly against top cover, then tighten lock screw.
4. Remove setting probe and measure gap between knurled portion of probe and sliding member.
Then refer to chart ‘A’ and check that gap is correct in relation to ambient room temperature.
    
                               
      Setting probe in position
A—Probe inserted at hollow grub screw position, needle lift adjustment
B—Sliding member
C—Knurled portion of probe
D—Probe hole for main valve
E—Main valve adjustment position
F—Lockscrew
G—Probe removed
H—Feeler gauge		        
                               
 
Gap for setting probe for Ambient room temperature of  
.050 in. (1,25 mm)
.040 In. (1,00 mm)
.031 in. (0,80 mm)
.022 in. (0,60 mm)		 50F (10C)
60F (15.5C)
70F (21C)
80F (26.5C)		  
Chart ‘A’—Probe gap and room temperature for jet needle lift setting  
     
                               
  5. If gap is incorrect use screwdriver end of alignment bar, Part No. 605999 to adjust hollow grub screw up or down to achieve the correct gap on the probe.
6. To measure the main valve opening insert the probe through the hole in the middle of the top cover and operate probe as previously described. This time the gap indicates the distance the valve is off its seating.
7. Now refer to chart ‘B’ and check that gap is correct in relation to the ambient air temperature.
If the gap is incorrect adjust as previously but this time use the grub screw adjacent to the centre probe hole.
    
  Setting main valve and jet needle lift
A—Probe hole, for main valve
B—Main valve adjustment
C—Alignment bar and screwdriver, Part No. 605999
D—Hollow grub screw and probe hole for jet needle lift adjustment
               
Gap for setting probe for Ambient room temperature of
.045 in. (1,15 mm)
.038 In. (0,95 mm)
.030 in. (0,75 mm)
.023 in. (0,58 mm)		 50F (10C)
60F (15.5C)
70F (21C)
80F (26.5C)
Chart ‘B’—Probe gap and room temperature for main valve setting
   

8. When setting has been completed seal all three recesses in top cover using new aluminium plugs.

Replace polypropylene heat insulation cover. It is important that the plugs are a good air-tight fit in the top cover.