Topic: 750 heads

[fritzer_108]

The head on my 1973 cb750 is toasted...warped, cracked, and leaking oil everywhere. I found a $90 head  in great condition from a 1977 cb750...will this fit my bike?

[bryanj]

Whats a 90 head? And the later 750 had a different oil return path

[fritzer_108]

Sorry for the typo...that was meant to read $90.

[Don R]

Avoid the 77 f head for sure, I'd try to stay 73-76.   Cycle X does a mod to make late heads not leak oil I'm not sure what it's about.

[Medyo Bastos]

Frankie runs a late f head running external oil lines


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[madmtnmotors]

The 77/78 CB750K heads use a bigger combustion chamber with slightly domed pistons. The 77/78 CB750K head with early flat top pistons will drop compression just a little but it will work. The 77/78 CB750F heads will give you heartburn unless you run it with the 77/78 CB750F cylinders or have the heads worked to deal with the two exposed cylinder studs.

EZPZ 

[PeWe]

I found a 392 head that had chamber sizes 22.5 - 22.9 cc.
I had expected more.
392 is upside down. I had a thought that it could have come from an Auto or K7.

It looked crappy, but mechanically sound except bad ex guides as used CB750 heads often have.
http://forums.sohc4.net/index.php/topic,180468.msg2128689.html#msg2128689

This is the head my K6 has now after restore this year. All guides  replaced, stock guides adapted for higher lift. Ported, new valves, springs etc.

If bores are tired, bore +0.5mm, use K7 pistons with a 392 head. Work fine with stock K6 head too (300), better compression.
www.cruzinimage.net sell a complete K7 piston kit for $120US + shipping.