Topic: CB750 Engine year identification

[Rob M]

I have an engine that has had the engine number ground off by some previous owner, I have to get a head due to a thoroughly botched attempt to drill out an exhaust mounting screw again by said previous owner.  So I was wondering if anyone could help me identify year by any other identifable features.  I had heard that certain oil passages changed around 76 or so switching heads had to be pretty year specific. Oh and frame is titled as a 1972 k2.

Thanks rob.

[Old Scrambler]

If the head has exhaust spigots and multiple posts in the fins on either end, as well as a notable curve in the fins above #1 and #4...........its a probably the original motor to the frame. The posts changed to a single and the curves changed to a slight bend in the early K3 series.

[754]

Yes on what OS said.
73 has all straight lines on front edge of top fin..and looking from side of motor..3 rectangular struts between fins, 72 & edown has 4 or more round ones..

[Rob M]

Thanks guys.  Well it looks like it is after 72 because it has no curve in the top fin over 1 and 4.  Is there any way that I could tell if it is before 76 when I think it would be a different head gasket?

[Rob M]

It has spigots though, like the 72.  Any other hints?

[Rob M]

Looking at the parts fische agin this evening it looks like it may be later than 76, it has a straight top fin and a smoother base for the cylinder cover on cylinder 4.  The fische shows a slight bump there for the cover mounting bolt.  Which sucks because I just ordered an earlier gasket set today.  Haste makes waste, i guess. 

[754]

Maybe 74,  and 75 and later have the "shift pattern" cast into the shifter cover.

[Rob M]

Thank you guys for narrowing this down for me. 

Today has been a nightmare of previous-ownerness for me.