Topic: Same speedo ratio but different drives?

[Scott S]

 This recently came to my attention and has me going 

 All the SOHC4's use the same 2240:60 speedo ratio (I'm specifically talking about 550 and 750 here, though).

 The 550 generally has a 120 MPH speedo.
 The 750 generally has a 140 MPH speedo.

 The speedometer drives have different part #'s.

 750 = 44800-300-030
 550 = 44800-323-000

 Are the drives different? Is that what makes the speedo face accurate to 140 MPH vs. the 120 MPH?
 I'm having a bit of a head scratcher moment wrapping my mind around a speedo that uses the same ratio but different drives.
 If you bolted a 750 speedo onto a 550, what would happen? Would it be off? And vice versa.

[seanbarney41]

This is a  head scratcher.

I am sure I have used a 750 wheel on a 550 before, but I don't remember clearly if I swapped the speedo drives over or not.  I am leaning towards not, I think I left the 750 drive on the 750 wheel, threw it all on the 550, and had no issues with the speedo.

We know that Honda will create new part numbers for some pretty insignificant reasons sometimes.

[scottly]

The 2240:60 ratio means that when the speedo cable is turning 2240 RPM, the speed is 60 MPH. This also means that for each mile traveled, the cable rotates 2240 times. This ratio is common to many Honda models.
The drives on different models have different ratios to allow for different diameter tires. As long as you use a drive matched to the tire size it was designed for, any speedo should read accurately, or at least as accurate as Honda speedos go.

[Scott S]

Weren't the 550 and 750 front wheels the same? Did they use different tire diameters?

[seanbarney41]

they are the same

[scottly]

Tire sizes, too? I have compared a 400 drive (with an 18" front wheel) to a 750 drive, and there is a difference in the gearing.