Having a bunch of trouble with my crankset coming loose this year. It's an FSA omega crank and just has a bolt in the left arm. Tried using locktyte and it still came loose but the bolt head was some what stripped so I thought maybe I wasn't tightening it enough. Bought a new bolt and the problem isn't gone so I'm assuming the problem is in the crank shaft. Anything else I should try before buying a new crankset? I'm assuming it's pretty trashed now because it's been ridden a bit with the crank loose. My BB bearings seem to be fine and my front derailer doesn't appear to have damage from this. Will a shimano crankset hold up better? Saw this problem show up a decent amount in forums when it first started happening and I searched online.

I'm on the larger side for a rider 6'1 195 so I'm slightly worried at this might a continuous problem after X miles on a crankset. Maybe this crankset just isn't all that great though.

If you do decide you're going to get a new crank, you'll also need a new bottom bracket or adapter. You either have Omega MegaExo 19mm or BB30, neither of which is compatible with Shimano 24mm, although from your description I'm guessing it's the BB30 one.

Is the non-drive side arm wobbling on the spindle, or is there play in the crank-to-bearing interface that allows the whole crankset to move relative to the bottom bracket?

The whole crankset moves relative to the bottom bracket.

Thanks. Hadn't checked yet if I needed a new BB too if I switched.

If SkyDog75's suspicious is right, the issue is that it could be missing a wave washer, or something is out of spec causing the wave washer to not take up play effectively.

2lo8 knew where I was going with that line of questioning. If the whole crankset moves relative to the bottom bracket, the problem might not be that your crank arm is coming loose, but rather you've got play between the crankset and bottom bracket. One of the most likely causes for that would be something like a missing wave washer.

The linked PDF has an exploded diagram of an FSA Omega MegaExo crankset and bottom bracket. (Not sure if it's your exact crankset.) The wave washer is #6 on the diagram.

https://www.fullspeedahead.com/wp-con...0110401_v6.pdf

Even if the bolt in the left arm is coming loose every time?

It likely stripped when over tightened. One needs to be 'very' cautious when pulling
or replacing both cranks & pedals. A cross-threaded quarter turn can become a real
nightmare, especially in aluminum. As for your problem, I am not optimistic. 'Possibly'
a self tapping bolt a mm larger might miraculously work.

Another reason to invest in a torque wrench and appropriate adapters, here an allen wrench to socket. My first experience with
this was with an FSA crank in 2005, sans torque wrench. First ride L crank loosened up, bolt disappeared somewhere in the
first 8 miles of the ride. Had to one leg it back to the car. IME it would be REALLY HARD to cross thread the oversized crank
fixing bolt. Stripping same would require a lot more torque than FSA suggests. Loktite should have worked also. And of course
neither the bolt or the axle are aluminum. The crank is and the hazard there is mis-fitting the splines and slicing off the splines
while tightening up the bolt.