A few months ago, I ordered the two timing gears from Amazon. Unfortunately they did not carry the 30 tooth gear with a 5/8-inch bore, or key-way. Since I was using a 5/8-inch diameter crank shaft, I had to bore it out , and then cut a 1/8-inch key-way. Both operations went surprisingly smoothly, though I did have a bit of trouble with a dull 5/8-inch drill bit, which I promptly tossed away. Below is some photos of the gear being modified.