Topic: 750 vs 550 gauges

[Shtonecb500]

I just took apart what i think is a larger 500/550 tach to practice removing the ring to replace the face. I want to replace the faces of my 750 instruments, currently a blue 750ss set with a green face patina set. Before I take the instruments off my bike and dissemble them, i noticed the 750 faces two screw mounting holes are a shorter distance apart than the 500 tach face i was practicing on. Is that the case? is the difference only between 550/750? I'm asking because I'm running 750 SS instruments on my 750 and was going to reface them with earlier green patina faces, the ones that don't have the jewels in the faces. I'm under the impression the motor had heavier springs so the red line on the 750ss tach is higher, replacing the faces would put me back in line with my k4 motor.

Do i need to just get an earlier set of gauges and reface those?

[grcamna2]

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[TwoTired]

The early CB500s in the US had small dials.  They went to larger dials in 1973, and continued as large dials for the 550.
I know the tach ratio for the CB550 is different than the 750, as I purchased dials to replace the wrecked ones that came with my 74 CB550.  Thereafter, I could never get the engine to rev to indicated redline.  ...Until I eventually replaced them with actual 550 Gauges.  While I haven't actually tried it, I would expect a CB550 gauge on and Cb750 would read higher indicated than actual RPM, because of the wrong ratio.  I believe the Speedometer ratio is the same for 750 and 550 though, as long as you don't change the front wheel size.  I know the 76 gauges were light green on both these USA models and darker on all others years with some differences in marking style.

Red lines for the CB550 remained the same throughout at 9200.

Red lines for the 750 varied somewhat.  I know the F bikes of 77-78 had higher red lines than K model due to the changes in valve train.  I'm not sure about earlier 750s, as I don't have any.

[Shtonecb500]

ill crack open one of mine tonight and see if the faces fit.

[Shtonecb500]

The early face and SS 750 faces have the same width between their set screws. I swapped my patina faces in, used a dremel to carve both ends of the opening for the odometer to fit all digits, you can see before and after below. I rolled my odometer back to zeros as well just to give it a shot. The two spoons to pop the needle worked a treat. Used silicon adhesive around the seal and those chrome covers hold everything together snug.

[Shtonecb500]

my odo isnt free spinning so i think i have the little C clip jammed.

[Little_Phil]

if I reset the ODO I set it a couple of miles below 00000. Then check it with a power drill when still apart. Hope it's something simple and you haven't stripped a gear.

[Shtonecb500]

if I reset the ODO I set it a couple of miles below 00000. Then check it with a power drill when still apart. Hope it's something simple and you haven't stripped a gear.

it started working today lol.