Can the harmonic balance come loose?

Oh wow, that's the coolest right there!! Well, that reminds me of an engine I got in a package deal with a car. The engine was in pieces and I believe was mated to a 4-speed gearbox at one time. At any rate, there wasn't enough clutch pedal freeplay (my theory) and you should've seen how the crankshaft got shoved forward, right into the main thrust bearing! It looked like about a 1/4" got "hogged out" of the crank AND main saddle!

You're not running a stick shift, are you?