Hi Norm.
I recollect hearing unkind comments about the quality of the Iron Horse

The Pot Metal Horse??
Still, might be worth the punt.
The original Suzi M120X weighs the same as the full-crank Victa (150 gm less on my scales).
Worth pursuing fixing your original? If the bore/piston scored from straight fuelling, nah.
So fuelling is mostly their weak area.
Not just the difficulty of ultrasonic cleaning of the original gummed up Mikuni carb, the throttle spindle can wear the carb body too.
The Carbie Doctor is selling Mikuni substitutes on eBay for $40 (eBay item number:331786948199), free postage.
Pricey, yes, but maybe worth a go?
It might be cheaper in the long run than fiddling about adapting Chonda carbs as some folk have attempted in the states.
Just a thought.