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Author Topic: Speedometer calibration  (Read 598 times)

AussieDave

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Speedometer calibration
« on: October 13, 2013, 06:56:41 AM »
It was raining today and I had the day off so naturally I decided to tinker with the Enfield . Some months ago I was whinging about my speedo being out . It used to read about 100 k at 60 and around 140 at 100 k . It's easy to remove as most of you probobly know, just remove the headlight, undo the drive , bracket and disconnect the loom and out she pops.
« Last Edit: October 13, 2013, 07:18:29 AM by AussieDave »
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

AussieDave

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Re: Speedometer calibration
« Reply #1 on: October 13, 2013, 07:03:34 AM »
 Getting into the unit was a bit more difficult . I ran a small flat head between the silver glass retaining ring and the housing and with a little persuasion the glass and rubber seals came off. Undoing the two Phillips head screws at the back releases the mechanism which can then be removed through the front of the housing.
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

AussieDave

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Re: Speedometer calibration
« Reply #2 on: October 13, 2013, 07:16:50 AM »
The speedo has a spindle that carrys the needlle at one end and a small solid magnetic wheel at the other, and rotates against a delicate coil spring. It's driven by a magnetic bell housing that rotates with the cable drive, the magnetic field rotates the wheel that sits inside against the tension of the spring. The speedo can be adjusted by relocating  its position on the spindle, as this sets the initial tension that the magnetic field drives against. I used a sharpie to mark the wheel at its resting point with the needle removed to provide a reference point.
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

AussieDave

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Re: Speedometer calibration
« Reply #3 on: October 13, 2013, 07:29:03 AM »
It took me three attempts to get it right, putting the disassembled mech back in the bike doing test runs . The needle is a push fit it , goes back on fairly solidly. Putting the unit back together was a bit fiddly , as you can see the back of the silver glass retaining ring carries a few marks from its deformation. I now have an accurate speedo. Thanks to whoever it was that suggested moving the needle was the way to go, all those months ago. You were right!
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

AussieDave

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Re: Speedometer calibration
« Reply #4 on: October 13, 2013, 07:32:58 AM »
Back in the bike , and alls well. Took it for a ride on the freeway and its spot on
  That's my workshop .
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

AussieDave

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Re: Speedometer calibration
« Reply #5 on: October 13, 2013, 07:38:51 AM »
Sorry about the punctuation .
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

Catbird

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Re: Speedometer calibration
« Reply #6 on: October 13, 2013, 08:08:43 AM »
Nice work -- I'm glad it worked out for you.  ;)

Since inaccurate speedometers are a widespread issue with our REs, it's rather surprising that the factory doesn't incorporate a fix.  And while they're at would it, I wish they would add a simple trip meter that we could use to help keep track of miles between fill ups. (Writing down the mileage on the handlebar clamp with a Sharpie works, but come on....).  ::)
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High On Octane

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Re: Speedometer calibration
« Reply #7 on: October 13, 2013, 08:50:23 AM »
Does anyone know if this procedure works on the old Vintage Smiths speedos?  Mine is grossly fast and it drives me nuts!

Great work and write up BTW.

Scottie


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singhg5

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Re: Speedometer calibration
« Reply #8 on: October 13, 2013, 10:56:58 AM »
That is good one.
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Royalista

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Re: Speedometer calibration
« Reply #9 on: October 13, 2013, 04:15:36 PM »
Excellent write up and well documented.

So, that's your workshop.
Next time I feel cramped I'll think of you and count my blessings.  ;D
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barenekd

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Re: Speedometer calibration
« Reply #10 on: October 13, 2013, 04:56:16 PM »
Quote
Does anyone know if this procedure works on the old Vintage Smiths speedos?

Take it apart and find out. They all work similarly, even if it's not exactly the same. I had a Yamaha one apart and instead of having the cup, it had an arm sticking up on opposite sides of the rotating magnet. You adjusted the speedo by the gap between the arms and the magnet. Closer increased the speed reading. The odos are mechanical, no adjustment.
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AussieDave

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Re: Speedometer calibration
« Reply #11 on: October 13, 2013, 05:08:36 PM »
Bare, that was the way I initially thought it would work too, as per the last time we talked about it. But I couldn't find any way to adjust the gap and the needle has to come off anyway to remove the faceplate. It's a bit hit and miss! There is about about a millimetre of play along the spindle axis which explains why it wobbles when I go over a bump .
 
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.

barenekd

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Re: Speedometer calibration
« Reply #12 on: October 14, 2013, 10:23:28 AM »
I saw in your photos that the RE one is different. The needle adjustment sounds right to me!
Bare
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Roeland

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Re: Speedometer calibration
« Reply #13 on: November 10, 2013, 06:05:18 AM »
I tried to calibrate a replica Smith's speedo. I have an electric 2 speed drill which runs at 2400 and 5800 rpm - worked out the gearing ratio - put a cable in the drill and speedo and adjusted accordingly. Spot on up 80 km per hour (checked with the GPS) - after that under calibrated - at 90 the GPS actually indicates 100 km per hour and at 100 the GPS indicates 120? The speedo also tends not to return to 0 and often hangs at either 10 or 20 when stationary? Did I do something wrong?

AussieDave

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Re: Speedometer calibration
« Reply #14 on: November 12, 2013, 12:05:12 AM »
I don't know Roaland . I think the initial tension needs to be set so the needle sit against the stop. I calibrated mine by riding and found that if I set it to read an accurate 60k it would read a little bit under at 100k . Thing is, the progressive spring tension needs to match the scale, and I don't think it ever does exactly.
"Glorious,stirring sight! The poetry of motion! The real way to travel! The only way to travel! ... O bliss ! O poop poop ! Oh my! Oh my!" - Toad of Toad Hall.