I was checking out this thread on the SOHC4 site, http://forums.sohc4.net/index.php/topic,162483.0.html
and ended up discovering something surprising (at least it surprised me).
Back when I was working on E100 I decided not to use the original cylinders. They had been bored to 1mm oversize and had a broken fin. I compared them to E1789 and found them to be identical. The engine wasnít going to be completely original anyway so I decided to use the E1789 cylinders. At least it would be correct.
Since I was using the E1789 cylinders I decided to use the matching head. It was in better condition than E100 and I found them to be identical too. So here comes the surprise. While looking at towers I happened to look at the E100 head (I saved it of course). Hereís pics.
Can you spot anything unusual?
Ding, ding, ding, ding. It is missing the outside spot faced holes that are under the towers! I canít believe I didnít catch that. According to the CB750-K2 parts manual only two of the small o-rings were required up to engine number 563. I know I had seen that before but I didnít know why. Now itís plenty obvious. I did a search and checked the distinctions and couldnít find anything about it. So here is one to add.
Obviously there are a few engines under 563 around and I canít believe Iíve never seen anything about this. The last thing I want to do is pull out E100. But you all probably know me by now and know that I canít let this go. When I get 97 back the engineís coming out. Iíll probably re-sleeve and repair the fin and use the cylinders too. Itís still at the Petersen until February 28 so I have plenty of time to get them both ready.