Most racers have multiple engines but most cars and boats have only room for 1 engine.
That means that 1 or more engines are stored somewhere in the racing gear.

The plastic bag where the engine comes in when brought new gives some good protection but it is not dust & oil proof.
With these 3 plastic 'safe storage plugs' which can be placed over the carburetor, fuel nipple and exhaust port to close them fully and keeping dust and debris outside the engine, and oil inside the engine.

These 'safe storage plugs' are sold in a package of 3 plugs covering all openings on the engine and are available for both 3,5cc/ 4,66cc engines and 2,10cc/2,5cc engines (NOVA/REX/TOP)

partnr 29065 is for the 3,5cc/4,66cc set;
partnr 29064 is for the 2,10cc/2,5cc set.