Remove the carburettor or throttle valve assembly, as applicable, which involves removing the throttle valve assembly on fuel injection models. For carburettor models, disconnect and plug the coolant and vacuum hoses, and disconnect the wiring from the preheater. In fuel injection models, remove the auxiliary air valve and cold start valve. Unbolt the intake manifold from the cylinder head and exhaust manifold on all models, and remove the gasket. Refitting is a reversal of removal, ensuring that the mating faces are clean and always fitting new gaskets. Top up the cooling system if necessary.