RE: How to get max rpm out of a tt 40
424 engine rules from the AMA:
1) Maximum displacement: 0.403 cubic inch.
2) Configuration: Stock, commercially available, front-intake, side-exhaust.
3) Intake: A single carburetor, as supplied by the manufacturer of the engine being used, with a maximum inner diameter of 0.325 inch. The carburetor shall be fully functional and shall be stock, except for longevity-enhancing modifications as follows:
(a) Adjustment screws and idle needle valves may be held in place with commercially available thread locker, epoxy, or other adhesives and safetied with rubber bands, wire, or plastic ties.
(b) Barrel retaining screws or pins may be replaced with commercially available screws or pins of harder material and may be held in place with commercially available adhesives. Barrels may be deburred for smoother movement and may be safetied with rubber bands, wire, or plastic ties.
(c) Throttle arms may be modified or replaced.
According to this, removing the spring from the carb and replacing it with fuel tubing might not be considered entirely legal, since the "fully functional and stock" would be violated. It looks like you can glue / loctite / all of the screws & such in place.
Is this what you're getting at, Dave? Just wondering.