Like I was saying earlier...I bought this spare head some months back. Found it at a friends shop in the yard. A pile of XS650 parts. Bought the whole pile. I recently disassembled the head starting with the valves. Seats and valves are in great shape. This head had very little wear since it was rebuilt. The rust was just on the surface and easily cleaned up. Dirt in the ducts was easily removed. Oxidation of the aluminum was tougher but not deep. Emery paper cleaned it right up.
Modifications
On XSCafe, I read about the 0 72 racing heads and they did not have the raised rings around the valves. They were ground off. I never liked them anyway. I imagine they were there to swirl the intake charge and promote a more complete burn. In my eyes, they also restricted the flow into the head. Out came the Dremel with a bead cutter head flattened that area out. I won't say it's all gone but most of it is. Wasn't hard to do. I practiced on a beater head I have.
On the exhaust end, where the pipes attached, There is a "lip" where the end of the pipe would be but, only about 1/2 of the way around. Both sides have this. Maybe this is to protect the end of the exhaust pipe from the flame of the exhaust stroke on that side of that side and not needed on the other or ??? Is this needed or can it be opened up for better flow. It's not a sealing joint. That's down the pipe on the outside of the tubes on the land where the studs are. The exhaust gasses would flow down duct and hit the pipe and have to go around the pipe end then down it. As it is now at least about 1/2 of the pipe end, there is a "guide" over it. I think I'll leave it alone. As for the lumps and bumps in the duct, I'm truing to flatten, smooth them over. Same in the intake duct. Just flatten/smooth them over. Nothing major. It's not to be a "Racing" head, just a city/back roads cruiser. Sometimes a "Spirited" run on the back roads. When needed. LOL.
Warning on the pics. The camera is not the best and worse so on the close ups.
