Originally Posted by
Turtle Speed
Am I right in understanding that the cause of this problem is an exaggerated case of a chainring that isn't perfectly circular? Is there any reasonably easy way to fix the issue without swapping over a crank/chainring from another bike?
Yup.
I've seen a lot of that with cheaper bolt-on rings made for the single-speed/fixie set, too. And I imagine it exists with many derailleur equipped bikes, too, except we don't see it because of the rear derailleur.
On a kid's bike I wouldn't worry about it as long as it isn't dropping the chain. Just pull the rear wheel tight, and if it binds when you spin the cranks, loosen it a bit.