Just got my son a MX650 and he already busted the rear sprocket. Razor is sending a new one under warranty. What mods or aftermarket part can be used to increase the strength and reliability of this item? He only weighs 50 lbs. I know this is sort of a common problem so just looking for some real world solutions. I don't really want to have to purchase a $50 wheel every couple of weeks, especially since my son is upset can't ride it till its fixed.