In my younger days I used to work on car engines and used carb cleaner for many of the parts and especially carbs. You can buy a gallon from the auto parts store with a small basket and soak your engine parts overnight in it and then wash with water and air dry and looks like factory new. Always break the engine all the way down before cleaning.

For the extra hard to clean you can use stronger chemicals, but carb cleaner will clean most anything on the RC engines. Sometimes I will use a paint stripper on the hard to clean parts then once that is removed I will drop it in the carb cleaner overnight.

Also, you can polish the componants with 3M ScotchBrite and make that puppy shineola sparkly and you will need sunglasses just to look at it! [8D] Just keep in mind when using automotive carb cleaner to remove any rubber o rings, plastics, and gasket material because the carb cleaner will soften or eat those materials up.