I noticed that the timing belt in my Timing Belt Motion kit from Radio Shack was riding on top of the teeth on the 90 tooth pulley. I measured its outside diameter as 2.292 inches. Stock Drive Products give the correct dimension as 2.272 inches. http://www.sdp-si.com/D265/PDF/D265T016.pdf . Perhaps your tool maker misread the dimension. The pitch diameter is 2.292 inches. The 18 tooth and 62 tooth pulleys in the kit are correct.
Can you supply correctly made 90 tooth pulley?