The temp sensor will limit the rpm's that your engine's "computer" will allow to just over idle. The only sound that you would hear should come from a buzzer under the dash. It wouldn't make any different sounds from the engine though. It would keep your engine from turning more rpm's than the setting from the factory. Suzuki does the same thing and I assume that those two aren't the only manufacturers that do that.
As for the molasses type stuff, that's probably oil that was inside your power pack to allow for cooling and corrosion protection. Calling a dealer or someone who works on these engines regularly would be your best bet for finding the parts.