When a bike is tuned the information is stored in the ECU in so-called 'Maps', these are just tables of numbers related to functions on the bike like fuel supply or ignition timing.  Bikes can be tuned in different ways to achieve different goals, for example to achieve more power or to achieve better fuel efficiency and lower emissions.  

Some ECUs allow you to store multiple sets of maps and switch between them while riding.  One map might be tuned for riding on the road (ie. normal conditions) and another might be for the race track (ie. performance mode).  These two maps are often referred to as MS0 and MS1 (MS = Map Select).

Map switching while riding is made possible by installing an electrical switch on the bike and connecting this to a specific pin of the ECU.  The exact pin to use depends on the specific model/year of the bike. 

The switching between maps is done by installing a toggle switch to ground onto a specific ECU pin (see below). One map will be selected when the pin is grounded, and another set will be selected when the pin is not grounded. You will need to test which maps are active for a particular switch position.

The following table lists known values for the map select pin of some common bikes, if you have information on other models that it not listed here please feel free to share:

2002-2007 Hayabusa: pin 21 (larger plug)
2003-2004 GSXR 1000: pin 21 (larger plug)
2006-2010 GSR 600: pin 53
2004-2005 GSX-R 600: pin 19 (smaller plug)
2004-2005 GSX-R 750: pin 19 (smaller plug)
2005-2006 GSX-R 1000: pin 57
2006-2007 GSX-R 600: pin 58
2007-2016 GSX-R 1000 : pin 66
2008-2019 GSX-R 600 : pin 66
2008-2019 GSX-R 750 : pin 66
2008-2019 GSX1300R Hayabusa: pin 58
2008-2012 GSX1300BK B-King: pin 58
2005-2008 SV 1000: pin 44 (small plug pin 10)
2009-2019 ZX6R (600): pin 51
2004-2010 ZX10R: Light Green/Black wire in KDS Diagnostic Plug
2006-2011 ZX14: Light Green/Black wire in KDS Diagnostic Plug
2006-2008 ER-6N: pin 46
2009-2015 ER-6N: pin 38 Green/Black wire in KDS Diagnostic Plug
2013-2015 EX-300: pin 38 Green/Black wire in KDS Diagnostic Plug