My speedo has always been off a bit but when I changed out the transmission output pulley to a 31 tooth it was out by 5-6 mph over 60mph. This didn't bother me as much as the odometer being off 12 miles in 200. I purchased the SIM -1 Digital Dakota calibration unit. The web site ( which now has been up dated) said it wouldn't work with 07's and above but after speaking with one of the the techs he told me the only difference was in the plugs and it just need to be soldered in after removing the plugs. I got the unit and did the install per the instructions. I adjusted the unit going down the road and was able to get it right on the money, milage wise as well as speed based off of my GPS. After stopping and re starting I found out that my 6th speed indicator light and my cruise control didn't work. I checked all the fuses and all was well. I called Dakota Digital and basically was told that to adjust it back down to where the Harley spec is 3-5% deviation and the indicator light and the cruise would work again. I tell the tech this was not conveyed to me during the purchase. He told me if the calibration was off before or at least in spec this unit will not make it any better. So I adjust it just to where the cruise now operates and the indicator for 6th comes on but I am back up to 3-4 miles an hour over and about 12 miles in 200. The installation process requires you to cut off the plugs that come on the unit off. When I told the tech once again that now that I have cut the plugs off I can't return it he goes and checks and tells me I can.... so I will. The web site has been changed to say that you will only be able to adjust the calibration to with in 3-5% of correct on 07's and later bikes. Does any one on the forum know of a re-calibrator that will work with out the cruise and the 6th gear indicator light going out......By the time I go to sell this bike when ever that maybe I will have driven only only 95% of the miles shown on the odometer!!!!!!!!

 

You might try this company in Australia that makes the "Yellow Box".

http://www.yellr.com/

I have had an older model of their devices on a Suzuki sport bike for over 10 years and it works like a charm. It uses a series of binary switch settings to calibrate to the exact mph.

I know they make one that works for HD, because I exchanged emails with them. I just have not gotten around to doing it yet. I don't know if it is plug and play or has to be spliced into wires....you could ask them. Also, I have no idea if their device works the same as Dakota Digitals, so the 3-5% variance / cruise / 6th-gear indicator is something you should ask them.

I am very interested in what you find....I was sure I was going to go with a yellow-box in the near future, but would not want to give up the cruise / 6th-gear lights (I have an 08 RKC btw). PM me with what you find out, I would like to follow this one.

 

I ran into the same thing on my 08 Ultra! I went with that Dakota that someone else was retrofitting the correct pins to the wiring. (the plug is not available)
What I did before I discovered that it wouldn't work was cut the factory wiring and install a small Deutsch Connector so it was a plug-in installation after I put the mating plugs on the Dakota unit.
What I will eventually is fix the calibration when buy the TTS mastertune.
http://www.mastertune.net/index.html
MasterTune-HD includes the following key features:

* Save and restore the original factory calibration
* Optional multi-vehicle interface
* Allows changing of factory speedometer calibration
* Preset limits to prevent adjusting values beyond reasonable settings
* Stores original and the last table saved edits so tuner can return to previous configuration
* Comparison functions quickly identify changed regions in tables
* Adjustment of front and rear cylinder spark advance
* Adjustment of front and rear cylinder volumetric efficiency
* Allows changing factory RPM limit
* Adjust for different fuel injector flow rates
* 2-D and 3-D graphing of tables to help visualize tuning maps
* Ability to print table graphs and table values