Hey Mark! Thank you for reaching out to me on this question!
#219 denotes the type of chain ‘pitch,’ basically the spacing from center-center of the ‘valleys’ between the teeth on the sprocket where the chain will sit / turn. Different sprockets match different chains, which have different chain pitches. For karting in general the #219 chain pitch and #35 chain pitch are the most popular.
Regarding bending over the axle, you should be able to bend the sprocket over the axle and it should return back to form once you do this. It takes a little force, but it is do-able. A handful of sprockets out there won’t return back to form, but these are not the case for most racers / sprocket types. If your axle seems too wide, you may have a 50mm axle, and I know it seems intimidating, but the sprocket will flex and return over these axles.