only do smuggling of new stuff from US
, but always have everything as checked-in luggage except for lipo batteries that i carry in my laptop bag.
Last time I had Venom race bag full of RC goodies including couple radios and it survived without single scratch (Phoenix to London to Prague). To save space I had most of the stuff unpacked and just thrown into the bag.
If you clean the motor well and rinse the tank you should not have any problems.
btw once i got back home i found can of soda in my laptop bag that travelled with me from London to Phoenix and back without single TSA guy complaining