Topic: What’s the difference between these cylinders??

[CB750R]

I keep reading on compatibility of heads/cylinders etc… I have my parts bike F2 motor torn down as well as my “K5” I built with Random EBay’d head and cylinders many years ago. I have both sets of cylinders cleaned up. And I can’t see why these can’t be swapped. The F2 cylinders have a cracked fin which is why I want to swap parts.

[70CB750]

78F cylinders have stud holes are open in front - two of them I believe.

I quess it depends what year is the F2. 

[CB750R]

Here is a clear answer to the question. It turns out in my case I’ve been using a set of f2 cylinders in my k engine for 12+ years.

Link to the answer is below:

https://www.cb750.com/threads/f2-750-head-and-barrell-identification.3419/?fbclid=IwAR0sM0Ap14TAzOS10w21jQByjeJuuEV_S39S8D8C6lrJ9HNFR4kJODzLYb4

[CB750R]

From that post above the head differences:

[Don R]

 I think to use the k cylinder between an F crankcase and F head will just leave the extra oil passage sitting unused. A K head and K cylinder may require the oil passage in the top of the F crankcase to be opened up to allow both oil returns to drain. 
 

[34barab]

Reason being so there's more oil longer on the valve train?

[HondaMan]

Reason being so there's more oil longer on the valve train?

Over the years, some have argued that be the point.
Personally, I think Honda was trying hard to save the last Yen on the castings, as the F2/3 was their riskiest build of the 750 and it was not at all certain that it would sell very well, given the track record of the F0/1 bikes. So, it was a stepchild in the Engineering Group. I believe some of the original 750K0 designers were called in to help work on it, and their designs were 'overruled' in the top end springs' retainers (which would have been custom parts) in favor of some common stamped-steel automotive retainers, suitable for 6300 RPM top speed. That became the Achilles' Heel of the whole F2/3 design in the end, and how many of them died.