by Mike Miller 7-28-2004

Note: Figures listed refer to figures in section 6M of the X7425 maintenance manual.


1. Remove air cleaner assembly and mounting stud.

2. Remove upper choke lever from the end of choke shaft by removing retaining screw (figure 11). Then remove the upper choke lever from the end of choke rod and choke rod from lower lever inside the float bowl casting.

NOTE: Remove rod by holding lower lever outward with small screwdriver and twisting rod counterclockwise.

3. Remove vacuum break hose, remove vacuum break bracket attaching screws. The diaphragm assembly may now be removed from the dashpot rod and the dashpot rod from the air valve lever.

4. Remove secondary metering rods by removing the small screw in the top of the metering rod hanger. Lift upward on metering rod hanger until the secondary metering rods are completely out of the air horn. Metering rods may be disassembled from the hanger by rotating ends out of the holes in the end of the hanger (See figure 12).

5. Remove two forward carburetor mounting bolts (1/2") loosen two rear bolts.

6. Remove nine air horn to bowl attaching screws; two attaching screws are located next to the primary venturi. (Two long screws, five short screws, two countersunk screws.) See Figure 13.

7. The air horn assembly may now be removed from the float bowl by opening the throttle valve wide open (use the throttle return spring) and lifting up on the air horn and turning sideways until the pump rod disengages from the upper pump lever as shown in Figure 14.

CAUTION: Care must be taken not to bend the small bleed tubes and accelerating tubes in air horn casting. These are permanently pressed into casting. Do Not Remove.

CAUTION: The pump return spring may jump out if pump plunger stays with the air horn. (Do not ask me how I know.)

8. Remove pump plunger from pump well. See Figure 15.

9. Remove air horn gasket from float bowl. You may need to use a small screwdriver to keep from damaging the gasket.

10. Remove pump return spring from pump well.

11. Remove plastic filler over float valve.

12. Remove power piston and primary metering rods by depressing piston stem and allowing it to snap free. Remove power piston spring from well.

13. If desired remove metering rods from power piston by disconnecting tension spring from top of each rod then rotating rod to remove from hanger as shown in Figure 16.

NOTE: If desired you may check the size of the main jets by removing the float and looking at the jets. The marking is very small and you may have to remove them and look with a magnifying glass. When done put everything back where you found it.


1. Install power piston spring into power piston well. If primary main metering rods were removed from hanger, reinstall making sure that tension spring is connected to top of each rod (figure 16). Install power piston assembly in well with metering rods properly positioned in metering jets. Press down firmly on plastic power piston retainer to make sure the retainer is seated in recess in bowl and the top is flush with the top of the bowl casting.

2. Install plastic filler block over float needle, pressing downward until properly seated.

3. Install pump return spring in pump well.

4. Install air horn gasket around primary main metering rods and piston. Position gasket over two dowels on secondary side of bowl.

5. Install pump plunger in pump well.

6. Holding the primary throttle valves wide open, (use the throttle return spring) rotate the air horn assembly so that the pump rod slides into hole in pump lever and then carefully lower air horn assembly onto the float bowl. Make sure that the bleed tubes and accelerating well tubes are positioned properly through the holes in the air horn gasket. Do not force the air horn assembly onto the bowl, but rather lightly lower in place. Close throttle valves.

7. Install two long air horn screws, five short screws, and two countersunk screws into primary venturi area. All screws must be tightened evenly and securely. See Figure 27.

8. Check for proper power valve movement with small screwdriver through float bowl vent.

9. Install two forward carburetor mounting bolts. Torque four attaching bolts to 15 ft. lbs. evenly and securely.

10. Install vacuum break diaphragm combination rod into the slot in lever on the end of the air valve shaft. Then install the other end of rod into hole in the vacuum diaphragm plunger. Install vacuum diaphragm assembly to float bowl using two retaining screws through bracket. Tighten securely.

11. Install rubber hose between the vacuum diaphragm and vacuum tube on float bowl.

12. Install the secondary metering rods to the secondary metering rod hanger. The ends of the secondary metering rods point inward. Lower secondary metering rods into float bowl cavity and place hanger on actuating lever. Install small retaining screw and tighten lightly and securely.

13. Connect choke rod into lower choke lever inside bowl cavity; then install upper end of rod into upper choke lever and retain the choke lever to the end of choke shaft with attaching screw. Tighten securely.

NOTE: Make sure that the flats on the end of the choke shaft align with flats in the choke lever.

14. Reinstall air cleaner stud and assembly.