Topic: Where's my jets?

[mycb750k6]

The picture of the K1 head shows the cam tower squirter jets in the center of the head. The K0 head doesn't show any jets per se, just holes that angle down to the main oil feed. Am I SOL??

[MCRider]

The early heads did not have the removable oil orifices, just holes. But the holes had stand ups that would support an Oring. Yours appear flush.

 The later heads had removable (though difficult) oil orifices which are unavailable from Honda so don't lose them.

BUT, I though the removable orifices didn't come out till K3. I'll have to check some microfishies.

Not much help eh?  Other than to say, that area went thru some changes.

[mycb750k6]

No actually a big help. Yes the K0 holes appear flush - just enough room for an O-ring but no stand up. Just a hole where the oil would come in at what looks like a 45 degree angle. The K1 has stand-ups it looks like. The H-man book shows pictures of the big orifices that fall out but there's no room in the K0 head for anything like that. Now I'm wondering if I can use this K0 head with the holes coming in at such an angle. What does it matter anyway as long as the towers get lubed?

[Whaleman]

My K2 has removeable jets. Dan

[mycb750k6]

OK here's a picture I took of a friends sand cast as he was assembling it. Looks like my K0 head. No stand-ups - just holes. Mystery solved???

[MCRider]

Well... I checked the fishies at Motogrid.com and they show the removable oil orifices (unavailable) on all 750s K0,1,2,etc. This is not true, but exactly where the changeup occurred I cannot confirm.

I looked thru HMs book and he acknowledges the before and after of the removable oil orifices and that different size Orings are used.

On another note, while reading the HM CB750 book, I confirmed that stock pistons were indeed flycut from the factory, with the twin flycuts on the exhaust side.

[mycb750k6]

I contacted H-man last night on the issue and this is his response as he's commented before that this K0 head appeared to be a sand cast:

"The very early sandcast heads had the jets in the cam bearings (metering holes, really), and only one side (the "inner" side) of each bearing was drilled to receive oil. This made them "left" and "right" bearings, which became the hermaphroditic versions we all know, even before the summer of 1969 was over. That is one early head! These leaked oil pretty badly around the O-ring seat that you can still see: the oil would push past the O-ring and polish the surface, leaving those shiny "seats".
Then they wouldn't seal for beans unless you installed a thicker O-ring.
I think the originals were 1.9x5.9mm, we used the 2x6 or 2.1x5.9 (hard to get today) instead, to pack it a little tighter.

If you try to install later cam bearings on that head, it will cause the crankshaft to starve for oil and the whole top of the engine will overfill and make a real mess..."

So I'm going to look this morning to see if I can see the jets in the cam bearings.