K1200GT Overheating Problem - K-Bikes.com - Excellence in Motion
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post #1 of 5 (permalink) Old Mar 8th, 2011, 6:46 pm Thread Starter
Join Date: Feb 2011
Location: Stockton on Tees, , UK
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K1200GT Overheating Problem

Has anyone else out there had this problem? I met it last summer whilst negotiating congestion round Lille due to roadworks, and later in Schaffausen. I originally thought it was possibly due to a fan problem, but the service report on my return told me the air passages were blocked by three and a half years of flies and mud. They would fit me a new radiator (at around £500 uk) or I could take the radiator off, soak it for 2 days in the bath and refit it after suitably careful cleaning of the fins. So I did that, and boy was it filthy. I used a combination of soaking in hot soapy water and Muckoff followed by spraying water through it from the back. Eventually I could see the fins again. Phew! (Thinking about avoiding a £500 bill). Then I came to refitting it. Well my workshop info tells me the coolant is replaced under pressre (reminids me of a Queen song) but I was assured it could be refilled without resorting to that (good job 'cos I aint got the necessary kit anyway) because there is a bleed screw on the lhs as part of the water pump housing. So I set to and carefully refilled it, and kept my fingers crossed as I started the beast up and let it reach operating temperature. The bleed screw allowed loads of steam to escape so it was out on the road before putting the panels back on. Oh dear, there was the temperature going way up again, so back to my garage where I bled the system some more then let it cool. A couple of hours later I checked the level and set off to road test it again, and surprise surprise it all worked.
I do think that BMW aervicing should include a rad clean when they do the valves and spark plugs, it would have saved me a load of hassle. i suspect that the 'S' modls and the 1300 will suffer from the same problem. Oh, I fitted a fender extender as well to try to reduce the amount of mud getting thrwon thrown the plastic guard.
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post #2 of 5 (permalink) Old Mar 9th, 2011, 4:05 pm
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The radiator surface area is minimum anyway on all the K bikes. They have to run the system at 16psi to squeeze any overhead they can.

I have been careful to run a spacer through the fins as they can get distorted and fold across the airflow. You can also get them aligned with fine needle pliers. A thin spray coat of lamp black paint also helps.

First thing most say when somebody has an overheat problem is check and clean the rad fins, the second thing is make sure the pressure cap is sealing good.

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post #3 of 5 (permalink) Old Mar 10th, 2011, 12:50 am
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The cooling system on these bikes is far more critical than most.
Because these are high compression engines. Bumping up the compression gives us more power AND more efficiency. But one of the costs is that they produce a lot of heat. While a lower compression engine might tolerate some clogged up cooling fins, it's much more of an issue on a high compression engine. That heat needs to be shed.
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post #4 of 5 (permalink) Old Mar 10th, 2011, 11:06 am
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My car has a high compression engine, more bhp and sheds its heat ok. It rarely moves off the engine stat temperature and when the fans come on, is still controlled at the engine stat. temperature very quickly. In fact you can see how quickly by watching the gauge dropping.

K bikes have no decent sealed shrouds around the fan housing, just right angle ducting which is very airflow lossy. The radiators need more surface area, but this is not practical unless you do what the Japs do and design the rads as a wrap around.

In Winter, the temperature you see on the gauge is the engine stat. temperature. When the gauge reads higher than this, the cooling system has lost control as there is either insufficient airflow from the fans at low mph, or insufficient radiator area to bring down the temperature at 50 mph plus.

Motorcycle designers started with airflow cooling and met all the problems of city riding as engine sizes got bigger. But they know that engines (especially oil) can take a certain amount of peak heat overload and unless you are the city despatch rider sort, you will soon be moving with enough airflow to bring the temperature down.So the K bikes can take some extreme temperature cycles - but that doesn't mean it's a good thing.

K bikes are Sport Tourers, which kinda lets them off the hook if you are a heavy city commute rider with average speeds in hot Summer less than 50 mph, or ride in city tunnels a lot.

The issue of compression ratio is not the main factor, it's also the amount of ignition advance used to get performance. If you retard the static ignition timing, even by a couple of degrees, there is less heat produced at the low rpm end.

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post #5 of 5 (permalink) Old Oct 31st, 2016, 3:13 pm
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Location: Luleċ, , Sweden
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Removed the side panels and front panel in front of the cooler and the fan. Little tricky with upper right bolt of the fan but not impossible,
Sprayed anti bug cleaning both in front of cooler and back. Then sprayed the cooler with low pressure water from the rear and out came a lot of sand and remains of mosquito’s ( very common on our area ) Was possible to clean the cooler w/o taking it out and refilling coolant fluid and underpressure bleeding and,,,,'
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