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Thread: 2003 K1200GT Temperature reading request for other K1200 2000-2004 bikes

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  1. #1
    Registered User
    Join Date
    Aug 2018
    Bolingbrook, IL

    2003 K1200GT Temperature reading request for other K1200 2000-2004 bikes

    I have a 2003 K1200GT with 27k miles on it. The gauge keeps reading a bit above the normal marking and did some readings.

    I wondered if a few of you would repeat my tests for comparisons on a similar GT or RS bike.

    Testing details: Bike on center stand idling from cold. Summer temperature here was 90s in the shade. I used a Harbor Frieght $26 Ames model with the factory default Emissivity setting of .95 . Not an expert on emissivity, but that was the factory default. I just pulled the trigger and it read out the digital number.

    I pointed the laser at the radiator top black metal curve both left and right sides. On the left side, just off to the side of the radiator cap. Right side, just on the curve. Reading is much different pointing to the hose, so stick to the black curved area.

    Instrument was resting on the plastic panels about 3 inches above the radiator.

    More definition: “midpoint” I am calling the normal center marking on the gauge. “3/4” is half way between the center marking and Red line. Red line is the Red line area.

    Per Clymer manual has “normal operating temps of 190F - 220F. Fans on at 221F and overheated light at 239F.

    My results to compare:

    Cold, reading was 90F both left and right sides. Gauge, no reading.
    After warm up idling - Left 200F, right 190F. Gauge at midpoint.
    Guage hits 3/4point - Left 220f, right 218F. Gauge at 3/4point.
    Fan on - Fans turn on with left side 224F, right 221F. Gauge 3/4 point.
    Fans on 3+ mins - Left 215, Right 205F. Gauge dropping below 3/4 point but not midpoint yet.

    Clymer spec and this infrared thermometer is telling me the bike is running in a normal temp range of 190 to 220 although the gauge is saying the bike is running on the hot side at the 3/4point. I wish the 220F on my bike was showing the midpoint on the gauge. For me, not happening.

    Let me know how your bike is showing. Much appreciaed.
    2003 K1200GT

  2. #2
    Registered User GTRider's Avatar
    Join Date
    Apr 2006
    Nibley, UT USA
    All of the RS/GT bikes of that vintage were at “normal” temp when the needle was somewhat above the white centermark. In stop and go traffic on a hot day the gauge would climb further, getting close to the red zone before the fans would kick in and cool the bike while heating the rider. In cold weather the gauge would read at or below the midline under normal riding use. It’s just the nature of these machines.

    There are a couple things to check, tho. First, let the bike idle while parked until the fans kick in, and verify that both are working. Secondly, check the radiators at every 12k service to make sure they aren’t packed full of bugs and such. And thirdly, replace the radiator pressure cap every few years as they do go slack over time. The caps are not overly expensive. And lastly, of course make sure the coolant level is correct in the catch tank and with a 50-50 mixture of the correct BMW coolant.

    My GT pulls a sidecar with two people and camping gear. Sometimes the needle is up, sometimes down, but never in the red when maintained as mentioned above. As to the exact temp it’s running—I don’t know and really don’t need to know; I just need to know that it’s not overheating.

    1983 R80ST — 1984 R80 G/S-PD — 2004 K1200GT w/Hannigan S/C — 2010 K1300GT — 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

  3. #3
    Registered User
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    Aug 2018
    Bolingbrook, IL
    My bike reaches 190 at the midpoint. It is barely warmed up. With the range of 190-220, 215F would be the proper normal midpoint. The gauge is messed up.

    I am wondering if other guys have the same reading. If everyone has the same 190F reading at midpoint, my chances of fixing this gauge are slim. Good to know though.

    I already did the coolant level check and using the proper 50-50 premixed coolant, no air. Radiator fins are clean and no leaks or loss of fluid.

    Parts changed or to change:

    1- Radiator cap changed ($20) No difference it temperature readings. Pressure seems to be the same as before and working.

    2- Thermostat not yet changed but with the Left/Right radiator temps being the same, odds are it won’t help. Mine is working ok as-is. This task is harder than expected to perform, so I will hold off on this. Everything I read is to leave it alone. I respect their opinions as correct thinking.

    3- Coolant temperature sensor ($27 part 62161459270) is an easy change. Not sure if that will help the gauge. If other guys are 190F at midpoint, Probably not a fix.

    4- Temperature sensor ($100 part 17111464985) is attached to the back of the engine block. Kirk Johnson has a video on replacing it. Might be a common problem. But again, if other guys are 190F at midpoint, Probably not a fix.

    My K1200GT is running great. Very satisfied and willing to keep polishing it up by replacing parts as needed. With the tempertature readings, I now know it just warmed up (190F) when at the midpoint. Go ahead and let her run. Hitting the 3/4point, the fans are cooling it down below 220F. The gauge is just messed up, nothing to worry about, well less stressful.

    Anyway, I am still interested if other K!200 are reading 190F at the midpoint.

    Thanks for the feedback. John
    2003 K1200GT

  4. #4
    My advice. Understand that gauges are relative and need to be used to observe changes and not to be seen as absolutes. As an aside, ditto this double or triple for tire pressure monitor systems.

    1. Look for changes in behavior, not numbers.

    2. Once a year spray the radiator with hydrogen peroxide and spray with hose water repeatedly to get rid of insulating bug guts and crud on the radiator fins. DO NOT use a pressure washer unless you wish to buy a new radiator.)

    3. Use quality coolant at the correct proportions and change per recommendations.

    (I put almost 400,000 miles on a K75 and the inside of the radiator was pristine after always using quality coolant. All of the crud was on the outside.)

    4. Ride the thing until unusual things happen.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell

  5. #5
    Registered User
    Join Date
    May 2008
    Western Massachusetts
    As said by others, look for a change in your bikes characteristics, not absolute numbers.

    My K-RS typically reads just below the mid-mark on the gauge, but I live in usually cool New England. Riding in traffic (a car in front of me) will automatically heat it up to just above the mid-point. Stop-and-go riding will get it up to 3/4 hot, with the fans coming on shortly there after.

    It has consistently behaved the same way for the ten years I've had the bike, so what those gauge reading translate to in actual temperatures is of no interest to me. It is obviously performing as designed. Should that change I'll get curious.

    BTW, if your interested is prompted by the amount of gauge movement, and its apparent sensitivity, you should know that it is largely a function of the engineering choices that BMW made back then. The more current thinking is to not both the rider/driver with too much unnecessary info. Most current gauges will move little or not at all despite real changes in actual coolant temperature, so long as the system is still operating within its design parameters.

  6. #6
    Registered User
    Join Date
    Sep 2019
    Silicon Valley

    Consider the source... of your temperature data


    I'll echo and amplify what others have said: It's all about RELATIVE temperatures. The other posts here have talked about the gauge readings being important as a relative (comparative) indication, not absolute. Well... the dirty little secret of IR (optical) temperature measuring devices is that the same is true of their output readings.

    Technical details:

    The emissivity has EVERYTHING to do with the actual number that it reads out. And emissivity is a notoriously difficult thing to pin down. It depends on the material whose temperature is being measured, that material's surface conditions and temperature, angle at which it is observed, among other things. The instrument, if decent, should give decent REPEATABILITY of its measured values, and give good indication of variations between things at different temperatures (which is hotter, and roughly by how much?) BUT... absolute numbers? Not so much, unless the instrument is pretty sophisticated AND has been recently calibrated, preferably on material(s) at least similar to those for which it is used to measure temperature.

    So, two things to keep in mind here:

    1) Consider the source of your temp readings. You're using a $26 instrument bought at Harbor Freight. Not so certain that that sucker is "precision" and has been calibrated beyond the barest basic in-factory tests.

    2) You're trying to discern temperature variations of 5-25 degrees Fahrenheit and draw therefrom conclusions about the validity of the indications of another relatively inexpensive gauge. You're probably asking the instrument to discern differences that are within the fuzzy-ness of what it can do. Suggest you take a look at any documentation that came with your instrument and see if it says anything about accuracy. Good chance that it won't, but if you do find something, that may give you grounding in what it can and can't do.

    Let me know if you dig anything up. The science and engineering behind these seemingly simple instruments gets complex in a hurry. (Not to throw rank, but I do know about this stuff: I have a doctorate in mechanical engineering and have worked with lasers for the past 23 years.) When you buy an el cheapo device that's supposed to do what a high-quality, high-complexity instrument MIGHT (or might not) be able to do, well... you get what you pay for!

    Moral of the story: don't be quick to conclude that your GT's temperature gauge is messed up. It may indeed be "inaccurate." But the chance of being able to verify that with the tool you've got at hand is, IMO, dubious at best.

    BTW, I consult my '04 K1200GT's temp gauge pretty much the way (and for the reasons) that other posters have mentioned. Nothing more.


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