Looking at the outer end of the head fins, do the vertical bars joining them look round or oval/rectangle ?
Do the carbs have cables coming out of the top?
Is there a shift pattern cast into the left engine cover, the shifter comes out of ?
My 73 has blank cases, they come as a pair.
The carbs do not have cables, there are linkages and the expected 'butterfly' 2-cable pulley that each carb linkage connects to.
Not only is the engine number missing -- the gearshift pattern is also not there.
I have a '71 head in the garage -- the '71 head has 5 (well it looks like 4 at an angle, but there's actually 5) vertical rods at each end of the head.
On this 'mystery' cb750, there are three verticals at each end of the head, not 5, and they are not rod-shaped -- the verticals are oval shaped.
Also:
- the clutch cover has 9 bolts
- it has hm341s
- the speedo and tach guages are not the later aqua/light green, they're the same darkish color as the early guages
- the speedo is incremented in 10s (10mph, 20mph, 30mph) whereas the earlier cb750s were incremented in 20s? I believe, but not 100% on this point........
- the ignition is under the gas tank on the left side -- it is flat, not sunken in.
I'm thinking this probably is, in fact, a '72 or a '73.
Didn't the ignition switch go up top in '74?