Not got another thermometer out to check but I would guess................Perhaps I need to get a bit more scientific and compare to another source......
Guessing is not good.
You need to adopt a clear experiment.
Buy a good quality thermometer.
Over the next year year take daily readings, preferably at the same time each day and hourly, recording:
(a) The temperature shown on the thermometer
(b) The temperature shown on your bike's read out
(c) Repeat both (a) and (b) on on the move and at rest. I would suggest a wait of at least 10 minutes when arriving at rest before taking the readings.
This will build into an excellent database, comparing your bike's readout against a known and accurate control. From this data it should then be reasonably easy to establish:
(1) The accuracy of your bike's readout against a known constant control point.
Of course this will only be relevant to your bike, so of little real use to anyone else. You could of course repeat the whole process each day and each time with another 1200 GS of similar vintage and, preferably, more than one. This will enable you to start building an accurate picture of the variance of not only your bike but others', too.
(2) Whether the error reading is constant as a fixed amount across the temperature range (for instance, always three degrees too high, which you feel is true) or whether it is a percentage deviation error (for instance, 3 degrees high at 10 = 30%. Whilst 30% high at 20 degrees = 6 degrees).
(3) How to then prepare a suitable formula to correct the errors found. This may well be as simple as the sums offered up in #2 or something more complicated.
Or of course you could just ignore it all and rely on your gut feelings of: It's bloody freezing, it's not that warm, it's quite pleasant, it's hot, it's bloody hot. Assisted by outside stimulation from your eyes, temperature sensitive nerve endings and the puddles of sweat (or ice) collecting in your shreddies; probably backed by reference to the local or national weather forecast.
Look forward to seeing your results next November
