Quick Fuel Technology 4500 Shaft Kits - Manual

Installation Instructions for Model 4500 Shaft Kits
1. First step in the process is to remove the original throttle shafts. This is a fairly simple mechanical
procedure, however there are a number of precautions that will be noted in these instructions to alert you to
potential problem areas. After removing the carburetor from the engine be certain to drain all the fuel from
the bowls.
2. Back out both idle mixture speed screws. These are located on the main body directly behind the throttle
lever 90 degree tab.
3. CAUTION: The original throttle plate screws are staked into place to prevent loosening. This staking
compresses the threads protruding beyond the throttle shaft. The safest process is to remove all of the
threads until almost flush with the shaft. This can be accomplished with a small hand file. These screws
are brass so it doesn’t take very long to remove the excess threads. The easiest way to remove these
threads is to hold the throttle wide open making it easier to keep the file parallel to the shaft. Other
methods can be used to remove the threads, such as an air sander, however, these remove the threads very
quickly so precede with due caution to prevent making contact with the shaft.
4. Turn the carburetor upside down, securing the air horn to prevent damage to the vent tubes.
5. Remove the Allen Head screws securing the intermediate linkage components on both throttle shafts. This
Allen Head is 5/32” and may be difficult to remove as the thread may have a thread lock coating. If the
resistance is too great to loosen the screw by hand, use a small propane torch or similar heat source to
liquefy the thread lock coating. Once heated it should be fairly easy to remove the screws. Set these
screws aside for re-use. Once the intermediate linkage screws are removed the throttle shafts will work
independently of each other.
6. Using the correct size Phillips head screwdriver, remove the throttle plate screws. When removing the
screws you will feel a little bit of resistance as the end of the threads begin to enter the throttle shaft. This
is normal. If, however, you feel a great deal of resistance do not attempt to “force” the screw out, file the
threads a little more as all the staking has not been removed.
7. With the throttle plate screws removed, you can now remove the throttle plates. Since the original throttle
shaft “sandwiches” the throttle plate, it takes some patience to pull the plates out of the shaft. With the
throttle wide open, attempt to pull the throttle plate from the bottom of the shaft. NOTE: The throttle
plates have a flat cut on each side of the plate that align with the shaft. It is important to pull the plate
straight as the flats reduce the plate diameter. If the plate turns, that is does not remain perpendicular to the
shaft, the diameter becomes greater, making removal more difficult.
8. If the plates cannot be pulled because they are too tight, try lightly tapping the top of the plate with a small
screwdriver handle or similar piece you can maneuver through the top side of the carburetor. We
emphasize lightly because the throttle plates have a beveled edge which can be distorted with too much
force. With time and patience the throttle plates can eventually be removed from the shaft.
9. Once the plates have been removed, locate the throttle shaft return spring. The spring has a 90 degree bend
that keeps tension on the spring. When removing the throttle shaft lift this tab so the spring doesn’t snap
back as it disengages the main body.
10. Transfer the spring from the original shaft to the new throttle shaft, note the hole location where the
original spring tab is positioned. Remove the original pump cam and set aside for installation later.
11. As you install the new throttle shaft be certain to feed the shaft through the intermediate linkage which may
have fallen out of place once the original shaft was removed. You can position the intermediate linkage
collar with a small screw driver or needle nose pliers. Push the spring tab forward as the throttle shaft is
close to its final position. Gently release the spring once it has cleared the pad on the main body.
12. With the throttle shaft in position, rotate the shaft to wide open, insert the throttle plate into the relief cut in
the shaft for the plate. NOTE: Position the throttle plate so the number stamped into the plate is up
(toward the top of the carburetor) and on the metering block side of the main body. If you look at the plate
from the top of the carburetor you can see the number stamped in the plate and it will be forward of the
shaft. It is easier to do one shaft at a time in this process.
13. Using the new throttle plate screws provided, use a #15 Torx screwdriver to position the screw into the
throttle plate hole and engage the threads in the throttle shaft. Start each screw into the shaft but do not
tighten.