I have been working on a Necchi Mira BU for the past several days and it has a Wonder Wheel attachment for it that has been giving me fits. Parts are hard to find for it and I did my research on how to replace the tire on it. It is large. 2" across with a 1" ID hole inside. I tried the fix that the Necchi Yahoo group suggested and had very disappointing results. I did it how I thought, and had excellent results. This is how it looks now.
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If you would like a kit, PM me, I have them.
~Grant~