Topic: 1973 cb750k rebuild

[73greenmachine]

Hello. This is the second time I’m attacking my 73 cb750. The first time I put in a new electronic ignition, cleaned and rebuilt carbs. After it sat for ten years this was enough to get it going. Was running but not smooth. If I went over 100km/h it would spew oil out a breather hose and onto my back tire. Cruising around town was good. It then only fired on one cylinder. I ended up buying a new bike so I could have a reliable ride. After getting married and having a kid I’m in the garage attacking this thing again. I’ve removed the top end and I am going to do a full seal replacement, new cylinder heads for a nice new fit. What else should I be looking at to do? I’d prefer not to get into the bottom end if not needed. The gears and shifting worked fine when it was running. Any help is much appreciated

[ekpent]

 Engine top end might be shot but when I had oil spewing on my back tire on a 750 project it simply turned out to be some insects had built nests etc. in my valve cover breather hose and totally plugged it up. Cleaned out the plug and was good to go.Hopefully you checked the breather components first. Here's a pic of some of the chud in the line,maybe a paper wasp or something.

[bochnak]

I have a bottom end video. See sig.