The saw itself is a factory refurbished unit I bought for $60.00 The sprockets are just regular parts from the 'hub/sprocket/belt pulley 'you weld it' stuff that a lot of places sell, nothing fancy. I went with a #35 chain and sprockets because of the tight area I had to get through. Some of the big old honkin saws have enough clearance for a belt and pulleys. Don't try to cut and weld on an old chainsaw bar, I did, and it won't work. What ever the outer layers are, the alloy gets real brittle right beside the weld and breaks very easy. So, I used what I had on hand, a 'U' shaped steel piece in place of the bar, (it was from a set of shelves, about 9 or 8 gauge thick. A bit less than 1/8th thick.) The arbour, bearing and shield are from an old off shore chopsaw that fried the brushes. The hole in the sprocket at the driven end was just a bit less than the teeth diameter on the clutch drum. Chucked it in the lathe and turned the teeth down to size, slid on the sprocket where the cutter chain would have road, and spot welded to each tooth. Put that part back together. Using one of the 'you weld it' hubs, I made it fit the arbour spindle by boring it out to fit the metric shaft. Put a key way in it, welded the second sprocket to it and assembled the works. Drilled the required holes and made standoffs so the shield would be positioned properly for side to side clearence. Put in a new blade, gassed it up and give it a try. The only thing I have to make a change to, is the outer sprocket, it needs to be as big as the room I have will allow. This thing would go into orbit if you firewalled it and let it freewheel. By gearing it down I can run it wide open, and be in the power band of the engine while increasing the torque. It was a bit of 'guess and by golly' engineering so I'm off the mark a bit that way. But, other than that, it looks like it will work as planned. A bit of lathe work is required, where the rest is regular cut, weld, drill. I had to offset the 'bar' by half an inch from the sloted tang that bolts on the saw so the outer hub/sprocket would line up, this would likely be different on other saws. With home brew stuff, no two are going to be quite the same.