Topic: Who knows CB750 K0 cylinder head vagiaries?

[Terry in Australia]

Well I'm about to kick off an engine build project. This came about because I sold my 1969 CB750K0 resto project bike and had a few left over parts lying around including most of another (earlier) 1969 K0 diecast engine, which I may use to power another "Bitsa" ("Bits of this, bits of that") bike.

I got lucky and managed to score a K0 cylinder head on Ebay with only minor damage (one busted fin) for the bargain price of $91, which arrived today:

Terry's Bargain K0 head 1 by terry prendergast, on Flickr

Terry's Bargain K0 head 2 by terry prendergast, on Flickr

Terry's Bargain K0 head by terry prendergast, on Flickr

Terry's Bargain K0 head 5 by terry prendergast, on Flickr

Of course it's absolutely filthy, but otherwise in good condition, so with a bit of elbow grease and some welding and machining, it should come up like new, or at least, good enough for me. Of course, after not seeing any reasonably priced K0 heads on ebay for the last several years, "when it rains it pours" and I did the "buy it now" thing for this head yesterday.

Terry's newest K0 head bought 19 Feb 18 by terry prendergast, on Flickr

Terry's newest K0 head bought 19 Feb 18.jpg 6 by terry prendergast, on Flickr

Terry's newest K0 head bought 19 Feb 18.jpg 7 by terry prendergast, on Flickr

Terry's newest K0 head bought 19 Feb 18.jpg 5 by terry prendergast, on Flickr

Terry's newest K0 head bought 19 Feb 18.jpg 4 by terry prendergast, on Flickr

Terry's newest K0 head bought 19 Feb 18.jpg 8 by terry prendergast, on Flickr

Terry's newest K0 head bought 19 Feb 18.jpg 10 by terry prendergast, on Flickr

Now looking at the pics, it appears that the second head is a much rougher casting than the first, and this reminded me of a comment made by one of the guys who were looking at the K0 project bike when I was selling it on Ebay, he said that with such a low engine number (1012XXX) "it should have a Sandcast head". (that head was one I bought on Ebay years ago, definitely K0 but a smoother casting than the new one I've just bought, in the lower group of pics) I thought at the time that all the heads were sand cast, but now I'm wondering if he meant that the low number diecast K0 engine should have had the same head as a sandcast K0 engine?

The engine I'm building is a lower number again (1010XXX) and having the luxury of owning two heads, I want to make sure I use the appropriate head when I build it, can anyone who knows the difference between K0 heads (if there really is a difference) educate me? Cheers, Terry.

[BPellerine]

Terry,I would clean them both off and see if there is any diff casting wise,but I dont know if you will find the answer,I have a 71 top end that is rough and dark grey compared to some others that are shiny,it also has raised circles beside each valve spring area,only seen one other,were they using a diff process for some parts?both diecast heads I have personally seen have been dark,did they even make a head using the sandcasting method,this ko stuff is like going down a never ending rabbit hole?bill

[Swoop]

Hi Tery,
There are some casting differences noted here.

http://cb750sandcastonly.com/support09.htm

Steve

[kmb69]

I would say that is an early version head based on the Sandcast Only info.
Thanks for posting that Steve.

[BPellerine]

so it looks like the top head in terrys post has no depressions and the bottom one does,so diff in that respect,but bottom one is smoother.

[Jerry Rxman Griffin aka MuthaF'er]

I don't know sandcast #$%* but I do know your second one seems to have some porting and a cracked spigot. 

[Terry in Australia]

Thanks men, some good info there, I'll wait for #2 to arrive and do some side by side comparisons. I hope it has had some porting Jerry, I found some high comp 836cc Pistons and a lumpy cam out in my garage, so this might be one quick K0!

[754]

How much was #2 ? I also have a set of 10,××× cases without topend.
 #2 looks painted,  I suspect its later than the other.
 And I am pretty sure they are both  made by sandcasting.

[754]

The raised letter are scratched intonthe sand core, I suspect.
 In the can tunnel pic of #2 you can see where a corner of the sand core broke off, showingbtye lump left behind.
 That can cause huge amounts of extra work when machining,  though not in this case.

[Terry in Australia]

Thanks Frank, #2 was also a bargain @ $200 "Buy it now" although the shipping was $93 more than the $75 it cost to send #1, so I'm hoping to get some of that back. That article that Swoop posted said that all the K0 heads were sand casted, but there are some differences between the early ones and later ones.

[Lostboy Steve]

Id like to think I know a lot about vagiaries.

BTW, I have absolutely nothing good to co tribute here.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

[BPellerine]

How much was #2 ? I also have a set of 10,××× cases without topend.
 #2 looks painted,  I suspect its later than the other.
 And I am pretty sure they are both  made by sandcasting.

so I wonder how long they made parts by the sandcast method,my 71 top end barrels and cyl look sandcast,not smooth and shiny like other heads I have.bill

[Don R]

 It's no help here but there is a type that has the pins between the fins cast as part of the fin, they are smooth on the bottom fin under the pins, There is also a type where the pins appear to be an insert put in the mold, on these you can feel the pin protrude through the bottom fin. I've found both types on early and later engines.
 Some are soft metal where a bent fin may be easily straightened and some are as brittle as glass. This might be due to annealing while in use. 
 I have an extremely early head and a couple later ones, I'll watch to see if I can help figure it out.

[Terry in Australia]

Thanks Don, feel free to post some pics of your heads!

[Terry in Australia]

Well the second K0 head arrived last week, so I degreased them both and the differences are a bit more obvious. All I need to know now, is which one is the correct one for my engine?

Degreased K0 Head 4 by terry prendergast, on Flickr

Degreased K0 Head 5 by terry prendergast, on Flickr

Degreased K0 Head 6 by terry prendergast, on Flickr

That cracked inlet spigot is more of a problem than I thought, I'd hoped that I could just remove one from an old buggared K1 head, but it turns out that the K0 spigots are around 4mm shorter? Poop!

Degreased K0 Head 7 by terry prendergast, on Flickr

[754]

Dont take it out, just get it welded..

[BPellerine]

the top head looks more like the diecast heads I have seen,with the triangle like recesss between 1 and 2 and 3 and 4,101xxxx engines.bill

[94thman]

Speaking of early heads, does anyone know when honda replaced the tiny oil jets with the kind you can actually remove from the head. The small holes are easy to plug, and I believe have cost me a cam and lifters in the past.

[BPellerine]

after 1972,they went to the more common ones you see,before that they had pressed in disc type with a screen on them,and on the heads above there is just a drilled hole.

[Terry in Australia]

the top head looks more like the diecast heads I have seen,with the triangle like recesss between 1 and 2 and 3 and 4,101xxxx engines.bill

Thanks Bill, I went back and re-read Swoops link, and in fact its the opposite, the one with the "Depression" between the inlet valves is the earlier casting, and the one without is the later casting, I presume (and that's dangerous) used on the later diecasts. I've sent an email to the Ebay expert who told me that I should have had a "Sandcast" head on the 1969 K0 (1012XXX) I had for sale a few weeks ago, hopefully he'll confirm. Cheers, Terry.

[Terry in Australia]

Dontvtake itbout, just get it welded..

Thanks Frank, I bought a fancy Chinese TIG welder with all the bells and whistles for my 50th birthday (I'm 58 on Sunday) and I never taught myself how to use it, so I better brush the dust off and give it a crack! (on something else less rare until I'm confidant enough to attack this thing)

[BPellerine]

hi terry,those depressions are on my 71 head also,while my 72 head does not have them,so on to a 74 head that does have them,so there were many diff moulds it seems,my 71 head looks like it was made with the sandcast process,but with front bolt.so what came first the chicken or the egg?haha,if you want a match,look at your cyls and see if they are rough or smooth,and match the head to the cyls.I have said this before,someone can tell you what came on their bike when it was new,but the next one down the line may be diff,swoops info says they started using diecast process at one time during ko.if you have a known org ko then you know what is org,if not we are only guessing is my thought.I will leave it at that.haha bill

[Terry in Australia]

No worries Bill, the EBay expert got back to me overnight, and yep, as per Swoops link, the heads with those depressions are the earlier heads, and were used on the first 15000 CB750's and K0's, so that one will go on my engine. (1010XXX) Cheers, Terry.

[BPellerine]

well at least you got an answer,still leaves me wondering about all the diff castings,including all the kos,glad I am not doing a 100pt resto!

[Terry in Australia]

Ha ha, I think I'll just put this engine together and sell it Bill, to finance my next CB750 build!