A mate wants the same mower fixed , as he saw me working on it. He likewise has spent $200 from same shop getting his mower fixed, but it only a mow or two, then doesn't rev.
speedy
Maybe you have just found half your problem speedy - two identical mowers that won't rev - both have had fixes attempted by the same shop
Not to say that there aren't inherent problems with the plastic carbys, but maybe they have done something that has turned what would be a easy fix, into something more strange.