Topic: Black motors -- Help me idenify the picture; Possible new F2 big-bore option!

[fang]

OK I forget.... Which of the motors were black from the factory?  Was it only the 1977+1978 F2 bikes?   I found an (ugly,old,dirty) black CB750 SOHC head online, and am trying to narrow down the choices of what it came off of.  The seller doesn't seem to know.  Here are the pics.  Can anyone tell me with some authority what these look like?






The reason I am asking is that I am fishing for a F2 cylinder head for an odd project.  I have been hunting for a big-bore replacement Piston, and I think the 1980's Kawasaki GPZ pistons (non-turbo) might be a perfect fit.  However those pistons look like their domes might be a tad tall.  So I am looking for some big-valve F2 heads to see if I might have found a match made in heaven...

Thanks!
-fang

[754]

72 or earlier.

When you view that head from the side there will be 4 round bars going vertucally through the fins.

[fang]

I see that it has the old-style exhaust spigots, but thought they might have been added later.... 
So, you are pretty sure the head is not a '78 F2?

-fang

[754]

look at the line formed by the front edge of the top fin, and compare to 73 & later, and the end of the fins.

[upperlake04]

Fang - the 77/78F motors were black. They have 31 and 34mm valves.

[fang]

Thanks for all the quick replies.  That pic was helpful.

Yes, I knew the motors were black with big valves, but I was not sure if other motors also were black, and I could not identify that head from the pictures.  I really appreciate your help.

peace and grease.
-fang

[fang]

Any other opinions?  The seller assured me that he really believes this head is off a 1978 CB750.  Heck it is even written right there in yellow grease pencil....   My first indicator is the presence of those exhaust spigots instead of studs.....  I just sold a trailer-load of old CB750 parts.  It kind of figures that I would wish I had them for comparison as soon as they were gone!

I do not know how the F2 and F3 heads are similar and different. Upperlake, is that a pic of a F2 head?

Ok.  Thanks for taking one more pass at this thing.

[NitroHunter]

Also, the '77 & '78 (F-2) heads are marked '410'.
I don't know about the K models from those years.
 
But if it's written in yellow marker, ya gotta wonder... 

[upperlake04]

 Yes Fang, that's an F2/3 head. As NitroHunter says, the '77F & '78F heads are marked '410'.  The cast characters on the top fin between 2 + 3 intakes on my 78 750F reads HM inside a horizontally elongated oval and 410 to the right of that. The 410 is is in line with the camchain tunnel.

An F3 head,  arrow points to one difference

[754]

The one fang posted, Is a 72 and down, look at the top fin...front edge..


Heyy, it only been a bit over a Third of a Century that I have been able to tell if a 750 head  9from 40 feet away) is before or after 72, but you need not take my word for it...