I learned to do it in Spanish class by saying "butter butter butter" over and over as fast as I could.
Here's another tip: you know the phlegmy gkch sound that's in German and such? Make that same sound, except put your tongue behind the top of your teeth and allow it to vibrate.
Oftentimes there's not enough air going past the tongue to make the tip of it trill - it's not a strength/muscle movement, but more like a flag flapping in the breeze.
Take a deep breath and sigh it out. As you exhale, keep your mouth slightly open, and bring your tongue up towards the roof of the mouth, with just the tip touching behind the top front teeth - not too loose, not too firm. You should get at least a little flutter.
Once you're happy with that, try vocalising as you do it, any noise will do.
With a bit of practice, you'll be able to do it tighter, with more control, and with far less air - then increase your dexterity with changes in pitch, and changes in mouth shape, and move onto actual words.
I used to think that I'd never be able to pronounce it. It took me a couple weeks of practice before I could actually pronounce it properly and easily. There's a video about it by someone with the YouTube channel called 'LatinTutorial'. That one is by far one of my favorites. Good luck!
One CAN (and sometimes does) name the fuel driving the motor, one can also name the vehicle (or other contraption) being driven by the motor. But even in English a motor and an engine are often the same thing, The devices you named are eksplodmotoro and elektramotoro
Steam engine = Vapormotoro
Gasoline engine (especially if one wishes to distinguish it from the internal combustion engine) = Benzinmotoro
Diesel engine (this one is different) = Dizelo
Locomotive (train engine) = Lokomotivo
Engine room = Maŝinejo
I hear a very distinct trill between sur and radoj. I hear a lighter, but still distinct trill in motoro.
R's are a bit tricky, partly because every language seems to have their own way of creating that sound. To many Europeans the American R sounds like a vowel, the Brits get accused of that too. The Germans have a very guttural R, while the Spanish and Italians usually just use a light trill. sounding, often, to American ears like a D. In this instance the trill was light on motoro and emphasized on the effectual double R between sur radoj.
But hey!, Good catch.