Bonneville America Forums Forums Technical Forums General Tech Speedo error

Anyone checked into correcting the speedo error on these bikes yet? I checked mine the other day and it is off approx
10 mph or maybe a little more. I did a search of the archives
but didn't find any fixes for it. Anyone ask the dealer
about the problem.

How did you "check it"? 10 mph, at what speed? Have not heard of any fixes, but have heard about an 'error', speed is so subjective.....

I just put 1K miles on mine this weekend with my GPS along for the ride. The speedo is about 10% off across the range. At 75 mph, for example, the GPS indicates actual speed of 66.5

I hate it but that's typical for all bikes except Harleys.

There are two ways to fix it. The easiest is to find a gear drive reduction like hot rod car builders use to mate a Chevy trans to a Ford engine.

Another option which I've seen used on other bikes is to permenantly modify the magnetic field of the speedo's ring magnet. This can be done using a magnet from an old hard drive (very powerful) but it requires extreme skill to not over do it.

I've been searching for the exact gear drive converter but have not yet found the right combination of thread size and reduction.

The speedometer error is really frustrating. The worst part is that it was probably built this way on purpose. I recently changed my speedo so now I don't worry about it anymore. The gear drive converter would also alter the odometer and trip meters. Although my speedometer was 10% out, my odometer and tripmeter were dead on. If I'm not mistaken other poeple have found the same thing, so the drive converter doesn't really sound like a great solution to me. Altering the magnets is probably the way to go if you can manage it without doing any damage. For $300 you can get a dakota digital unit that has speedo, tach, trip and odometer, 0-60 and quarter mile times, and a buch of other features.

http://www.dakotadigital.com/Detail.cfm/-/Category=66/PartNumber=HLY-3016/product.htm

Or for $20 you could use a sigma BC-800.

On the bright side; when the Office asks "DO YOU KNOW HOW FAST YOU WERE GOING" you can truthfully answer, "heck if I know." He will then give you the info needed to do mental calculations in the future.

Older speedos had an adjustable connecting point for the needle return spring. Just move that till you get a proper reading.

Of course, the hard part is getting the speedo head apart. There is a gauge rebuilding company on the west coast, which does older Triumph speedos and tachs. They might be able to help with this.

If a guy had an "old" speedo to play with, I'll be he could determine where to drill an access hole so he could get at the needle return spring anchor. Then, using a dental pick or o-ring pick, move that anchor point to give a proper reading.

To finish, install a small, black rubber plug in the just-drilled hole.

Do older Triumph models use somewhat the same speedo? A fellow in a "big city", where there's bound to be a motorcycle junkyard, could get one to play with. Once he figured it out, he could do this mod for others (and maybe do ignition box rev limiter mods, too).

Greybeard, Dinqua, Grump, Sal Maglie, Arsenalfan, I hear destiny calling one of you....

I would pay big money to anyone that could calibrate my speedo. I hate it being off.

I just pretend that my speedo is correct. It makes me feel like I'm really fast.

I'm with you nuthin, I can hit the ton in 3rd gear right before the rev limiter kicks in.

Mine is spot on at 0. From there on, it seems to increase in error to about + 10 mph at an indicated 40, and seems to hold that to as fast as I'll go. Once, I passed a radar wagon that has a huge display showing your speed. It said 42 and my speedometer said 52. I wish I could use the tach to determine my speed, but it's off the other way, showing 6800 when I hit the rev limit.

Finding a way to recalibrate would be great I'll have
to start searching out something. I don't even know
exactly how far off I am. They put radar warning signs up
all the time here but nowhere that I can get a run at one
doing 60 mph. I just got beside my buddy in his truck to
get a rough idea. In the mean time I can be a tough guy
and tell people "Yeah I do 80 in school zones on my bike."