[Columbia13]

Hi
The speedometer on my 350 iron ci bullet reads too fast, for example when I am doing 30mph it is reading nearly 40mph.
I have checked this with a speed app on my phone.
Is there an easy fix?
Cheers
Michael

[tooseevee]

Hi
The speedometer on my 350 iron ci bullet reads too fast, for example when I am doing 30mph it is reading nearly 40mph.
I have checked this with a speed app on my phone.
Is there an easy fix?
Cheers
Michael

           You'll soon get paragraph after paragraph of answers to this question.

            My answer is No. There is no easy fix. They're all wrong. There are just too many variables in a cable driven speedometer. None of them are/is correct.

            We never worried about it much until telephones became speedometers.

[Adrian II]

Is there an easy fix?

A genuine Smiths chronometric speedometer, not an Indian replica, properly calibrated for whatever size of tire which you're using - 3.25" x 19" front?

The speedo drive position was changed from its traditional home on the rear wheel to the front wheel some years ago, but the factory kept the same 2:1 drive gears.

A.

[Karl Childers]

Luck of the draw maybe? My inexpensive replacement speedometer from H's seems to be right on. There are several radar activated speed warning signs in my area and my new speedometer reads the same as their display. My other bikes and trucks with known accurate speedos read the same,  + or minus - 1mph. Not entirely helpful but it seems at least some of the repops are good.

[Columbia13]

It's not bugging me enough to buy a new clock (which still might not work anyway) so I think I'll just live with it. I know exactly where 30mph is on the dial and the protests from the bike tell me when I get anywhere near 60!
Cheers Michael

[Karl Childers]

It's not bugging me enough to buy a new clock (which still might not work anyway) so I think I'll just live with it. I know exactly where 30mph is on the dial and the protests from the bike tell me when I get anywhere near 60!
Cheers Michael

I understand that, mine wasn't working at all and I mainly wanted a replacement for the odometer to keep track of the miles, as you mention if you are familiar with the motorcycle by sense and feel you pretty much no the speed you are going.

[AzCal Retred]

My speedo reads differently depending on air temperature, the spinning cup/magnet assembly inside either changes position or the grease drag changes. The engine will tell you what speed it's happy at on the open road, traffic will determine in town speed. It's an 18 HP machine designed in the 1940's for 60 octane war-era fuel that likes to comfortably run 45-55 mph in 4th, depending on prevailing wind & road grade. Speed wasn't a big issue then, they were just glad they weren't walking. Let your machine talk to you and enjoy the ride! 

[mrunderhill1975a]

I have always assumed that the optimistic speedometer reading was a design feature to encourage the rider to slow down before the rod breaks through the case.

[Richard230]

I thought it was RE's way to make the rider think they were going faster than they really were.    Cheap horsepower. 

[zimmemr]

I don't know if this is still accurate but it might be one way to go: https://www.motorcycleclassics.com/classic-motorcycle-repair/install-a-smiths-digital-speedometer/ And he uses a Bullet to demo the install.

I've also seen Smith's replica's that use a sensor mounted on the rim and recently I ran across a BSA with a speedo that used an internal GPS to monitor the speed. According to the bikes owner it was expensive but dead accurate. It had a more modern look to it that you might not like but it didn't look out of place on his A65 Lightening.

[AzCal Retred]

For $10 - $20 the wacky world of consumer bicycle electronics will solve all speed/distance measuring issues with clinical accuracy....just program in the wheel rolling circumference and you are on your way. Put the read out in an inconspicuous place (steering stem?) and most will think it's a clock. Or the real thing, between $200 - $500, plus calibration costs, plus proper interconnecting cables....   I dunno, but the 0-80 MPH Hitchcocks drop-in unit for about $50 USD looks pretty good to me! 
https://accessories.hitchcocksmotorcycles.com/accessory-shop/Speedometer-Old-Style/37813
PART No. SM1006 ; SPEEDOMETER 80 MPH, BLACK FACE ; £38.50
This is an Indian made speedo that is similar in appearance to the old Smiths Chronometrics fitted to a range of British bikes in the 1940, 50's and 60's.
3.1/8" (80mm) diameter and can be fitted in a cowl or platform mounted. It has a single illumination bulb but no provision for any other warning lights and a chrome rim.
Dimensions: 80mm diameter of main body ; 50mm deep (measuring under the rim to the base of the body) ; 65mm stud centres

https://www.amazon.com/SY-Bicycle-Speedometer-Waterproof-Multi-Functions/dp/B01HL0B5AU/ref=sr_1_5?dchild=1&keywords=Wireless+Mountain+Bike+Computer&qid=1630643626&sr=8-5

https://www.amazon.com/DINOKA-Speedometer-Waterproof-Automatic-Multi-Function/dp/B07XD2TGPQ/ref=pd_sbs_3/137-4872847-0397733?pd_rd_w=5OeIf&pf_rd_p=0a3ad226-8a77-4898-9a99-63ffeb1aef90&pf_rd_r=F0ZCSKPZYFD6DAZK5K17&pd_rd_r=b26308ed-6e88-4050-9342-8de28cb9fe10&pd_rd_wg=Hrqbu&pd_rd_i=B07XD2TGPQ&psc=1

https://www.ebay.com/itm/185023980125?hash=item2b1449e25d:g:TZ8AAOSwwMRfkZxX
Smiths Chronometric Motorcycle 125 MPH Speedometer with Brass Bezel
Condition:New
Time left:Time left:3d 06h  |  Monday, 4:28AM
Starting bid: ; GBP 89.00

[tooseevee]

For $10 - $20 the wacky world of consumer bicycle electronics will solve all speed/distance measuring issues with clinical accuracy....just program in the wheel rolling circumference and you are on your way. Put the read out in an inconspicuous place (steering stem?) and most will think it's a clock.

           I put one of those little bicycle computers on my last garage-built bike in the early 2000s & they work very well on motorcycles. Sigma-Omega something was the brand. Just J-B Weld the trigger to a spoke, mount the sender carefully & you're all set.

           I've mounted one on the Enfield, but have yet to calibrate it. I've got too many irons in the fire for my own good 

           The most important thing is measuring your tire circumference accurately. On the harley in 2002 or 3 I measured three full tire rotations on the driveway with chalk then divided that number by 3. From there it's a simple matter to program that number into the unit.

[Richard230]

           I put one of those little bicycle computers on my last garage-built bike in the early 2000s & they work very well on motorcycles. Sigma-Omega something was the brand. Just J-B Weld the trigger to a spoke, mount the sender carefully & you're all set.

           I've mounted one on the Enfield, but have yet to calibrate it. I've got too many irons in the fire for my own good 

           The most important thing is measuring your tire circumference accurately. On the harley in 2002 or 3 I measured three full tire rotations on the driveway with chalk then divided that number by 3. From there it's a simple matter to program that number into the unit.

I have done the same thing on my 2011 Bullet. A cheap accessory and once adjusted correctly, it is very accurate. But it does show how inaccurate the stock speedometer is. Not only its speed indication, but also the odometer.