If you want to get your carbs clean then you could use Autosolvol paste, you can put some in a container then add water & mix till it's runny then use a tooth brush to apply to the fiddly bits that are hard to clean, the only thing is that carbs are not meant to be shiny they are matt finish aluminium so getting them to shine is near impossible. As for the other engine parts like the casing there is no other way than elbow grease and time I'm afraid, even with an electric drill or polisher it takes time and patience, for those greasy bits use GUNK both tin and spray and just wash off the crud but it will never be factory fresh unless you strip it and start again. For cleaning and restoring plastics you could use T-CUT and polish when you get the worst of the fade out of it, someone else may know of other products that do a similar job but really it's down to hard work and time.