 Speedometer not accurate
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Joined: Jun 2012
Posts: 9
Complete Newb
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OP
Complete Newb
Joined: Jun 2012
Posts: 9 |
I have noticed my Speedometer is out by about 8-10mph and bounces around a bit at slower speeds. Is this a common issue and is it fixable
cheers
Rob
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Re: Speedometer not accurate
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Joined: Mar 2009
Posts: 12,964
Stickman Yogi
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Stickman Yogi
Joined: Mar 2009
Posts: 12,964 |
Our speedo's exaggerate... all of them. Some have been known to bounce around to the point of distraction or even uselessness. Had to turf my malfunctioning speedo.
Live to love, love to live.
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 4,073 Likes: 82
Loquacious
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Loquacious
Joined: Jan 2005
Posts: 4,073 Likes: 82 |
They are all off a bit but if it bounces at low speeds you might try lubing your cable.
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Re: Speedometer not accurate
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Joined: Sep 2010
Posts: 8,393 Likes: 1
Second Wind
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Second Wind
Joined: Sep 2010
Posts: 8,393 Likes: 1 |
Lube, it up babe. Graphite cable lube. 
I have no faith in human perfectability. I think that human exertion will have no appreciable effect upon humanity. Man is now only more active - not more happy - nor more wise, than he was 6000 years ago.
Edgar Allan Poe
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Re: Speedometer not accurate
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Joined: Sep 2006
Posts: 231
Adjunct
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Adjunct
Joined: Sep 2006
Posts: 231 |
My experience has been if it starts bouncing and the cable is OK, you are gonna need a new one. Happened to me at 8k on my America.
I was not happy to part with $250 for a part that should last basically forever.
Send lawyers, guns and money, cause the sh*t has hit the fan!
-W. Zevon
2020 Bud Ekins T100
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Re: Speedometer not accurate
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Joined: Jul 2006
Posts: 853
3/4 Throttle
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3/4 Throttle
Joined: Jul 2006
Posts: 853 |
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 6,821
Bar Shake
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Bar Shake
Joined: Jan 2005
Posts: 6,821 |
Quote:
Our speedo's exaggerate... all of them. Some have been known to bounce around to the point of distraction or even uselessness. Had to turf my malfunctioning speedo.
They don't exaggerate. They're just optimistic, that's all.
Contra todo mal, mezcal; contra todo bien, también
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Re: Speedometer not accurate
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Joined: Aug 2007
Posts: 10,730 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
Posts: 10,730 Likes: 5 |
Quote:
my Speedometer bounces around a bit at slower speeds. is it fixable
Rob
go fast 
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Speedometer not accurate
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Joined: Apr 2007
Posts: 3,063 Likes: 8
Loquacious
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Loquacious
Joined: Apr 2007
Posts: 3,063 Likes: 8 |
Quote:
$250 for a cable?...they are only $33 here:
http://www.bikebandit.com/2006-triumph-speedmaster/o/m17654#sch569270
I think he was talking about the speedo itself.
12 Rocket Roadster
03 Bonneville America
69 BSA Firebird Scrambler
73 Yamaha TX 750
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Re: Speedometer not accurate
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Joined: Jun 2012
Posts: 9
Complete Newb
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OP
Complete Newb
Joined: Jun 2012
Posts: 9 |
thanks for the replies - I'll learn to live with it :-)
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 11,126 Likes: 13
Should be Riding
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Should be Riding
Joined: Jan 2005
Posts: 11,126 Likes: 13 |
If you have a tachometer use that to judge your speed. Cinnamon Girl's speedo reads 5mph at rest.  And reads 15 mph too high when under way. With an 18 tooth front sprocket, here are the rough speed baselines all at 3K rpm 3rd gear 30mph 4th gear 40 mph 5th gear 50 mph Each 500rpm is a change of 10 mph. Say you are in 5th gear at 3500 rpms. You are going 60mph. If you have a 17 tooth front sprocket subtract 5mph from the baseline above. I too have learned to live with it! The only reason I still have the bad speedo on Cinnamon Girl is that she records mileage accurately.
Last edited by moe; 07/26/2012 6:51 AM.
Blowing gravel off rural roads
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Re: Speedometer not accurate
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Joined: Aug 2007
Posts: 10,730 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
Posts: 10,730 Likes: 5 |
Quote:
Say you are in 5th gear at 5500 rpms. You are going 60mph.
I'm running 70 mph at 4000 rpm with an 18 tooth in 5th gear 
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Speedometer not accurate
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Joined: Sep 2006
Posts: 231
Adjunct
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Adjunct
Joined: Sep 2006
Posts: 231 |
I was speaking of the speedo. First thing I checked was the cable. They are cheap, and should wear out faster. Isn't that correct Triumph, Inc? 
Send lawyers, guns and money, cause the sh*t has hit the fan!
-W. Zevon
2020 Bud Ekins T100
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 6,821
Bar Shake
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Bar Shake
Joined: Jan 2005
Posts: 6,821 |
Quote:
Quote:
Say you are in 5th gear at 5500 rpms. You are going 60mph.
I'm running 70 mph at 4000 rpm with an 18 tooth in 5th gear
At 5500 in 5th I'm going a tad over 80 with a 16/44.
Contra todo mal, mezcal; contra todo bien, también
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 11,126 Likes: 13
Should be Riding
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Should be Riding
Joined: Jan 2005
Posts: 11,126 Likes: 13 |
Quote:
Quote:
Say you are in 5th gear at 5500 rpms. You are going 60mph.
I'm running 70 mph at 4000 rpm with an 18 tooth in 5th gear
Where was my mind? Try 5th gear at 3500rpms = 60mph per table above.
5500 rpms in 5th gear is close to a ton. I'll edit my post...
Blowing gravel off rural roads
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Re: Speedometer not accurate
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Joined: May 2008
Posts: 740
Adjunct
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Adjunct
Joined: May 2008
Posts: 740 |
Try loosening the knurled connector on the back of the speedo about a 1/2 turn. When I had mine too tight it made a grinding noise and the needle bounced around too.
Putting a slightly larger front tire on helps make the speedo a little more accurate.
Bill.
"I spent a lot of money on booze, birds and fast cars. The rest I just squandered."
-George Best
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Re: Speedometer not accurate
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Joined: May 2010
Posts: 5,720
Check Pants
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Check Pants
Joined: May 2010
Posts: 5,720 |
"Putting a slightly larger front tire on helps make the speedo a little more accurate."
#1, A 120/70 dialed in my speedo on my '06 to almost an exact reading per police radar, don't ask me how I know this..
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Re: Speedometer not accurate
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
Quote:
Putting a slightly larger front tire on helps make the speedo a little more accurate.
That's funny. My speedo was always perfectly accurate, and seemingly the only one on here. But I mounted a bigger tire (per the advice given here) and now it is 5 mph too slow. I kinda miss my accurate speedo cause I get tired of constantly doing the math in my head. 
Fidelis et Fortis
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Re: Speedometer not accurate
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
And further about speedo's..., It's weird how so many people have such different speedo readings. It seems like a speedo should be a fairly simple instrument to get right and uniform. I guess I really don't know how they work, but it must be something more complicated than a simple gear drive mechanism. And one more thing. The OLD trumpets had REALLY crummy speedo's, and worse drive units. The drive unit worked off the REAR wheel, and traveled a cable all the way across the frame and up to the speedo. The drive units were a cheesy tin composition, and I never had one last more than about 10 K. And when I restored/built my old Triumph, I bought a "repro" rear drive unit which lasted all of 4 K. I finally gave up on speedo's on my old stuff. You ever have any better luck, Ian?
Fidelis et Fortis
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Re: Speedometer not accurate
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Joined: May 2010
Posts: 5,720
Check Pants
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Check Pants
Joined: May 2010
Posts: 5,720 |
The needle is moved through its range by a permanent magnet pushing it up the scale and a fixed/regulated amount of resistance to hold it steady, the faster the internals are spun, the more the magnet over comes the resistance. Must be hard to calibrate them consistently on a mass production scale? I guess if you need/want an exact speed reading, get an Acewell.
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Re: Speedometer not accurate
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Joined: Aug 2009
Posts: 2,580
Loquacious
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Loquacious
Joined: Aug 2009
Posts: 2,580 |
There's a road near here with an electronic gizmo that tells you your exact speed. Whenever I've gone past it, my speedo has agreed with the gizmo, so I guess mine must be accurate. 
Too old to die young, too ugly to leave a good looking corpse
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Re: Speedometer not accurate
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
Quote:
The needle is moved through its range by a permanent magnet pushing it up the scale and a fixed/regulated amount of resistance to hold it steady, the faster the internals are spun, the more the magnet over comes the resistance. Must be hard to calibrate them consistently on a mass production scale? I guess if you need/want an exact speed reading, get an Acewell.
Thanks for the technical info. I had no idea.
Fidelis et Fortis
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 11,126 Likes: 13
Should be Riding
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Should be Riding
Joined: Jan 2005
Posts: 11,126 Likes: 13 |
That explains why the odometer remains accurate when the speedo goes funky.
Blowing gravel off rural roads
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Re: Speedometer not accurate
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Joined: Aug 2007
Posts: 10,730 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
Posts: 10,730 Likes: 5 |
My speedo is spot on now with a 120/90 front tire, but my odometer is short by just under 3 miles per 100 since I went with the bigger tire. I figure it has probably shorted me around 600 miles at this point, but I don't mind.
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Speedometer not accurate
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Joined: May 2010
Posts: 5,720
Check Pants
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Check Pants
Joined: May 2010
Posts: 5,720 |
Quote:
That explains why the odometer remains accurate when the speedo goes funky.
So, I guess we can assume our odo s. are gear to gear and that would be why they read consistently, and as the speedo is a slipper clutch type mechanism, explains all the variations noted. BTW, after market speedos with the correct ratio and the 12mm cable attach are readily available and reasonably priced. Same config. as most '70-80 s Jap. bikes, if one decided to go with a different one. I am running a 1-7/8ths" mini on my '05, it was advertised for a XS 650 Yammyha.
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Re: Speedometer not accurate
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Joined: Jan 2005
Posts: 7,630 Likes: 7
Monkey Butt
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Monkey Butt
Joined: Jan 2005
Posts: 7,630 Likes: 7 |
The cheapest alternative is to put a GPS on the bike and use it as your speedo. Another alternative is to send your speedo to these guys in San Diego, they fixed mine. http://foreignspeedoinc.com/
We all like to think of ourselves as rugged individualists. But when push comes to shove most of us are sheep who do what we are told. Worst of all, a lot of us become unpaid agents of whoever is controlling the agenda by enforcing the current dogma on the few rugged individualists who actually exist.
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