Originally Posted by
Retro Grouch
I'm going to side with operator.
On brand new bikes a slightly loose left crankarm is way more common than it should be. The torque spec for that bolt is generally around 30 lb/ft. That's more than you are likely to achieve using a multi-tool or 6" long allen wrench. If that's the case, and you ride the bike without getting it fixed, you will hose your crank arm and it will have to be replaced.
I tried to tighten it with a 5/16 allen wrench socket bit on a 3/8" socket wrench. It was so tight I could barely loosen it to try to re-tighten it again. It is all the way in so I do not think it is cross threaded either.