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Smiths Speedometer reads 2X actual speed #614296
08/23/15 10:45 pm
08/23/15 10:45 pm
Joined: Aug 2015
Posts: 20
MASSACHUSETTS
E
Eric Costa Offline OP
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Eric Costa  Offline OP
BritBike Forum member
E
Joined: Aug 2015
Posts: 20
MASSACHUSETTS
Hello all,
First post here after lurking for a while. I recently purchased a 1965 Lightning from a gentleman who restored the bike partially. The speedometer reads twice the speed I am actually riding at (IE. I ride at 20mph, speedo reads 40mph) Upon purchase I was told the drive gear from the motor for the speedometer was the improper gear. However, the only gears I know of are 1:1 and 1:1.25 ratio, which wouldn't cause the speedo to read 2X, or possibly the speedo is not calibrated right - so with both errors are adding up its causing it to read 2x? Or the other possibility, it has the wrong speedometer. It is a Smiths, the face reads SSM5001/05 1000. Any help is appreciated, just trying to fix all the little bugs to make the bike better. smile
-Eric

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Re: Smiths Speedometer reads 2X actual speed [Re: Eric Costa] #614302
08/23/15 11:38 pm
08/23/15 11:38 pm
Joined: Oct 2008
Posts: 1,684
Canada
L
LarryLebel Offline
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LarryLebel  Offline
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L
Joined: Oct 2008
Posts: 1,684
Canada
Actually the 2 drives available are 1.25:1 (15/12) and 2:1. The 1.25:1 drive requires a 1000 turns/mile speedo and the 2:1 drive requires a 1600 turns/mile speedo. These numbers are on the face of the speedo after the serial number. You could change the drive to match the speedo you have or vice versa.

Re: Smiths Speedometer reads 2X actual speed [Re: Eric Costa] #614315
08/24/15 3:30 am
08/24/15 3:30 am
Joined: May 2013
Posts: 4,946
Rotherham - S. Yorkshire
Allan Gill Offline

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Allan Gill  Offline

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Joined: May 2013
Posts: 4,946
Rotherham - S. Yorkshire
Is your speedo drive off the gearbox or back wheel?
On the speedo drive within the gearbox there are different parts which are changed to suit different gearing.

You could also have the wrong speedo or it be out of adjustment


beerchug
Re: Smiths Speedometer reads 2X actual speed [Re: LarryLebel] #614332
08/24/15 9:32 am
08/24/15 9:32 am
Joined: Aug 2015
Posts: 20
MASSACHUSETTS
E
Eric Costa Offline OP
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Eric Costa  Offline OP
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Joined: Aug 2015
Posts: 20
MASSACHUSETTS
well that was easy, I have the 1000 turns Speedo, so I must have the 2:1 drive gear in the bike now. Just need to get my hands on a 1.25:1 gear then. Thanks!

Re: Smiths Speedometer reads 2X actual speed [Re: Eric Costa] #739875
06/25/18 9:53 pm
06/25/18 9:53 pm
Joined: Apr 2017
Posts: 42
Sheffield UK
S
semprini Offline
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semprini  Offline
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Joined: Apr 2017
Posts: 42
Sheffield UK
Wonder if anyone could throw some light on my speedo problem. The unit on the bike (A65S from Germany) is a km/hr one which flutters badly, so bought a repro grey-faced one from a classic bike company . Checking with my phone gps, it seriously under-read the speed. He sent a second one out, this one reads 24mph at an actual 30mph. My original is SSM 5000/04A 1000. The gearbox is stamped 2:1, the rear tyre is a newish 4.00 x 18. A new cable has been fitted. A sticker on the base of the repro says M=2.0.


a
Re: Smiths Speedometer reads 2X actual speed [Re: Eric Costa] #739908
06/26/18 3:05 am
06/26/18 3:05 am
Joined: Jan 2006
Posts: 1,973
Maryland
JD Offline

Moto-Amish
JD  Offline

Moto-Amish
Joined: Jan 2006
Posts: 1,973
Maryland
Assuming it's the correct ratio and if it's like the originals, there is an adjustment screw underneath. It's been a decade since I rebuilt my gray faced speedo, but if I remember correctly rotating this screw will adjust what the speedometer reads. Way easier than trying to adjust the speedo on my '73 BMW.


Josh
Re: Smiths Speedometer reads 2X actual speed [Re: JD] #739973
06/26/18 9:00 pm
06/26/18 9:00 pm
Joined: Apr 2017
Posts: 42
Sheffield UK
S
semprini Offline
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semprini  Offline
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Joined: Apr 2017
Posts: 42
Sheffield UK
Thanks for the tip Josh, but on this Indian repo there doesn't seem to be any adjustment. They have a smooth needle action though and the tacho version works fine, so it's puzzling as to why there should be such a large under-read.


a
Re: Smiths Speedometer reads 2X actual speed [Re: semprini] #740070
06/27/18 7:39 pm
06/27/18 7:39 pm
Joined: Jun 2002
Posts: 10,174
Scotland
S
Stuart Offline
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Stuart  Offline
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S
Joined: Jun 2002
Posts: 10,174
Scotland
Hi,

Originally Posted by semprini
My original is SSM 5000/04A 1000. The gearbox is stamped 2:1,

Wrong gearbox for the the speedo.

In easier terms, the original Smiths speedo. you're looking at reads to "240" (kph, 150 mph)? The 2:1 'box is for speedos. that read only to 190 kph or 120 mph.

Hth.

Regards,

Re: Smiths Speedometer reads 2X actual speed [Re: Stuart] #740077
06/27/18 8:54 pm
06/27/18 8:54 pm
Joined: Apr 2017
Posts: 42
Sheffield UK
S
semprini Offline
BritBike Forum member
semprini  Offline
BritBike Forum member
S
Joined: Apr 2017
Posts: 42
Sheffield UK
Hth, yes, it's a 190km dial. The seller assured me that the repro (120mph) is correct for a 2:1 gearbox.

It may be that I've been unlucky and had 2 faulty units.

Last edited by semprini; 06/28/18 7:23 am.

a

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