Re: za50 mods: 20 tooth and oil nub grinding
buy one, try putting it on, and just grind away at it until it, with a chain on it, fits. if you have a dremel, or even better, a die grinder, just grind away at the material. simple as that.
i've been able to fit 20 tooth sprockets with chain onto e50s with no modifications. 21 is a stretch. dont know if theres more or less room on a za50 case.