If the kart and, consequently, its components have been out of use for some time, it’s good to dedicate some attention to the engine as well. Again, the real difference depends on what was done before the break: if the gas and water weren’t removed from the fuel and cooling systems, they need to be refreshed; especially the fuel system, which will likely be corroded by the gas.
The radiator shouldn’t present particular problems, apart from micro-blockages caused by mineral deposits. Even a float-type carburettor doesn’t require any particular inspection, but, if any gas remained inside, you need to empty it and replace the internal components.
You certainly need to inspect the fuel pump and replaces the filters and membranes: the operation is very simple; all you need is a screwdriver and a few minutes.
But if your engine has a membrane carburettor, you also need to replace the membranes which may have been damaged by the corrosiveness of the gas.
The gas lines will probably have yellowed, but it isn’t a problem: they lose transparency, but not their ability to transport fuel. You do need to check, however, that they haven’t been crushed or deformed.
These operations are not fundamental to the kart’s basic functioning, but they certainly matter if you want it to perform at its best.