3. The TQ phenolic bowl is hated by some, but it actually helps keep the fuel cooler, whic
Similar to the earlier AFB and AVS, the ThermoQuad is configured in a stacked arrangement of main body, which contains the integral bowls, an upper airhorn assembly. Unlike its earlier brothers, the TQ features a separate lower throttle plate assembly. These three main assemblies are held together by ten bolts at the top of the carb. Disassembly begins with the removal of all of the linkages, the secondary/choke dashpot, and any ancillary devices or solenoids. We like to remove the metering rod assembly before separating the major castings. Once inside, it is clear that the majority of the components are incorporated into the airhorn assembly. Lift the corner of the gasket, and pull the float pins, floats, and needle and seats. Pull the plastic accelerator pump transfer tube, and then the body gasket can be removed. The secondary jets have flats on their sides and can be removed with a 5⁄16-inch wrench. The accelerator pump plunger is knocked out from the top after the "S" link is removed, driving the plate and check valve assembly out of the bottom of the pump well. In front of the choke plate, you'll find the accelerator pump discharge nozzles, with a check-needle beneath.
The other two major castings have comparatively few parts. The main body contains the primary jets, a baffle plate in the secondary bores, and a pair of O-rings in the main wells. At the base plate, you'll find the metering rod step-up lever and pin, as well as the idle mixture and fast idle screws.
4. Note the huge proportion of the secondary versus the primary throttle butterflies. The
Disassembly Mistakes and Trouble Spots
Disassembly of a TQ is really pretty straightforward, though damage usually happens when it is forced apart. A common error is forgetting about the two body fasteners behind the choke in the primary barrels. Sometimes, even when all the fasteners are loose, the gaskets can stick, keeping the carb from coming apart. Never pry a TQ apart, since the phenolic bowl will crack or break. Usually, a few light hammer taps around the aluminum airhorn will free it. The fast idle link from the choke countershaft lever down to the throttle linkage is best freed by bending back the top lever just enough to release the link.
When removing the primary jets and inlet seats, use a correctly sized screwdriver with a slot wide enough to fully engage the part to avoid mangling the brass. The primary jets can sometimes be frozen in the body, and we have seen excessive force here rip the thread insert right out of the phenolic body, destroying it. Penetrating oil, or in extreme cases, an acidic solution can be applied to the backside of the jets via the main well transfer passages adjacent to the primary barrels. Carefully inspect the main body, especially for loose or leaking primary well buckets which are factory epoxied to the underside of the main body. Contrary to the popular myth, the main body is rarely warped, though it is subject to breakage and cracking, especially after becoming brittle over decades of use.