1981 XS1100H Speedometer Info

[JosephM]

I am replacing the speedo on my bike with a smaller gauge. I had previously asked about finding one that would work and I was referred to Mike's XS. Unfortunately, I did not see any there. However, ETB Instruments custom makes speedos for $100. The need to know:

Differential / final drive ratio (e.g. 3.92:1)
Speedometer cable worm and drive gear ratio inside the gearbox (e.g. 3.43:1)

Several folks on the forums told me that the ratio is 2.93:1. Is that the Differential/final drive ratio or the speedometer cable worm and drive gear ratio inside the gearbox? What is the other value that I need?

[Nightengale]

aftermarket speedo

I am replacing the speedo on my bike with a smaller gauge. I had previously asked about finding one that would work and I was referred to Mike's XS. Unfortunately, I did not see any there. However, ETB Instruments custom makes speedos for $100. The need to know:

Differential / final drive ratio (e.g. 3.92:1)
Speedometer cable worm and drive gear ratio inside the gearbox (e.g. 3.43:1)

Several folks on the forums told me that the ratio is 2.93:1. Is that the Differential/final drive ratio or the speedometer cable worm and drive gear ratio inside the gearbox? What is the other value that I need?

I have looked alot foor my project and i think that a small gauge for a 21inch front tire has the same ratio as the xs 1100 (60mph/2240rpm) i think, and they are on ebay for about 60 bucks

[crazy steve]

I am replacing the speedo on my bike with a smaller gauge. I had previously asked about finding one that would work and I was referred to Mike's XS. Unfortunately, I did not see any there. However, ETB Instruments custom makes speedos for $100.

Several folks on the forums told me that the ratio is 2.93:1. Is that the Differential/final drive ratio or the speedometer cable worm and drive gear ratio inside the gearbox? What is the other value that I need?

The XS/XJ speedo is driven off the front wheel, and the ratio is 2.93:1. For each turn of the wheel, the cable turns 2.93 times. There's nothing inside the motor/transmission/final drive that has anything to do with the speedo. For more info, read this thread: http://www.xs11.com/forum/showthread...t=speedo+ratio

I'll also note that a 21" and 19" front tire have very nearly the same rolling diameter, so there's no 'ratio' difference there...

[cywelchjr]

The XS/XJ speedo is driven off the front wheel, and the ratio is 2.93:1. For each turn of the wheel, the cable turns 2.93 times. There's nothing inside the motor/transmission/final drive that has anything to do with the speedo. For more info, read this thread: http://www.xs11.com/forum/showthread...t=speedo+ratio

I'll also note that a 21" and 19" front tire have very nearly the same rolling diameter, so there's no 'ratio' difference there...

I guess maybe they are assuming that the speedometer runs off the rear wheel through the transmission like a car? Then those other things would all play into things, but with it driven off the front wheel nothing matters but the cable drive ratio.

[crazy steve]

Yeah, some of the older Harleys were cable-driven off the transmission, and that method has made a comeback although with electronics now. But no help here....

[TopCatGr58]

Hey Joseph,

You must not have looked in the right place on Mikes.net.... see this link:

http://www.mikesxs.net/products-46.html#products

They are in the Accessories/gauges section.

BTW, our tachs are electronic, not mechanical, but they read a signal from the ALT...1 leg of the 3 phases, not ignition spark pulses. Mikes has electronic units, but you'll need to connect a tap to one of the ignition coils for the right signal....and IIRC, you'll need to select 2 cylinder mode on the gauge for it to count the signals correctly for the proper RPM readout.

T.C.

[crazy steve]

TC, Mikes hasn't got a single speedo listed with the right ratio for a XS11 (or for a 650 for that matter, if they share the same ratio), in spite of what they say.

Here's the math....

A typical 100/90-19 tire has a diameter of about 25.8". Circumference is about 81", or 6.75 feet. Divide that into 5280 feet (one mile) and you get 782; that's how many revolutions the tire makes in one mile. So if the tire turns that many, plugging in your ratios tells you how many revolutions the cable makes in one mile...

2.9:1 ratio, 2.9 x 782 = 2268
2:1 ratio, 2 x 782 = 1564
1.5:1 ratio, 1.5 x 782 = 1173

So if you're going 60 mph, the 2268, 1564, etc is cable rpm.

Mikes lists one speedo (03-0760) as having '60MPH=2240RPM' which would be a good number, but lower in the description says its a 2:1 ratio. That defies the math, sorry. Any of these will hook up and read, but the 2:1 versions will read about 1/3 fast, the 1.5:1 versions about double...

A 21" tire differs in circumference by less than 3 inches from a 19", so you won't see any help from that either. That will get you cable rpm numbers of 2190, 1510, and 1133 at a true 60 mph.

[JosephM]

Thanks

Hey, folks. Thanks for all of the advice - good stuff to know. But a real pain. I am seriously considering scrapping the speedo and going with an electronic tach. I just didn't like how big the stock instrument cluster is.