Rodeobob, you are correct in that you must let the cast cool down very slowly. Careful welding in short runs helps keep the temperature of the surrounding cast down therefore helping teh cooling process. The other problem is the weld material and the fact that 'normal' weld material will be very brittle after welding so will always be a weak point. Using stainless as the filler material helps as does brazing.
In my case iot was clear that the previous welding had not allowed a slow cooling process so cracks were evident around the weld and I was not happy about running it like that so I opted for making a new piece and bolted that to the cast iron pulley. I have to say that it works very well and unless you look very closely you wouldn't know that I had made it!
I'm going to scan the documents of the HD8 and will let you know when I've done that. They will be ideal for you as they match your model HD8 and do help me with mine even though they are not for my model!
I'm still trying to find out what engine I should have on mine, narrowed it down to a Fuji (Robin) but what model number. I was thinking EY18 but that has a 3/4" output shaft so maybe it was an EY20 as I think that had a 1" one.
