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Thread: K75RT Heat Control: Is it possible?

  1. #1
    JohnWC
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    K75RT Heat Control: Is it possible?

    Finally got my K75RT back on the road. Great bike, runs well, but.... the heat on my legs is ridiculous. Exactly like one of the main reasons I sold my R80RT: it was like having two space heaters trained on my lower legs going full blast. I read the posts on this. Apparently it is a well known problem, although BMW engineers seemed to have missed it when they designed and tested the bike. My question: can anything be done to fix this? Can you block off, from inside, the three slots in the long rubber pieces that come up against your legs? Can you do as one person said, get 1 1/2" foam pipe insulation and fit it in around the top of the hollow tube that is that last air chamber near your legs?( the one the rubber pieces fit into) I already have the heat blanket under the tank, and I don't notice a problem under the seat or on the tank. If you block off all this stuff, can it affect the engine cooling? Will removing the lowers solve the problem, but if so, don't you need to fabricate parts to support the main fairing, and the radiator cowling?

    I am mystified how BMW ever sold more than a handful of these bikes, unless it was to Eskimos.
    I'd like to put the guys who designed these bikes on them and make them ride through the Arizona dessert for three days in the summer.
    "Ooh mah God! Deeze deeesiine eezz terreeble! Back to Berlin!"

  2. #2
    I've owned my K75RT since 1996 and have ridden about 77,000 miles with it. I've seen a lot of heat "solutions" through the years. I had K100 heat shields for a while, if you can find a set they work well.



    I find if I move my knees (rdalland air wings) out from behind the fairing I get a lot of cooling air. In warm weather I find myself riding with my kneecap resting on the edge of the fairing. The turbulence keeps things cool behind the fairing. When I ride in a more spirited fashion, I stay tucked in behind the fairing and don't really feel the heat. I also have a summer windshield, a stock shield cut down to allow air to hit my chest and shoulders. With the vents of my jacket open, I stay relatively cool while moving. In traffic, all bets are off - you are going to sweat.

    ride what you've got; enjoy the ride!

    Turbo Fluffy Motoclub - IBA 50182 - BMW MOA 69187

  3. #3
    Dum vivimus vivamus ted's Avatar
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    They do get hot at times. When was the last time you changed your coolant? A gallon of the BMW purple stuff and crush washers (and might as well rebuild the radiator cap while you are at it) will run under $30 or so. Some folks have added a manual fan override button to switch the fan on earlier and keep it running longer (and cooler), others have modified the bike to make the fan come on at a lower temp. I just cleaned the road grime out of the radiator (along with the remnants of a dead bird there was a lot of crap in there - nothing simple green, a toothbrush and wet vac couldn't handle) and changed the coolant, seemed much more bearable afterward.
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  4. #4
    JohnWC
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    I'm trying to imagine where the k100 heat shields would go. When I put the lowers back on, I carefully glued and refitted 1/2' round backing rod, slit down the middle to the edges where there was some old foam. I just finished changing the coolant, although I used regular Prestone with the recommended 60 water/40 coolant (for supposedly better cooling). I can't tell if the fan is coming on at all while riding. I know the shaft turns freely by hand. I don't know about riding with my knees out. I'll give it a try. I have a very tall windscreen on this bike, and a very low Corbin seat. Great wind protection, but no breeze.

    I can't really tell where all the heat on the legs is coming from. I would think most of it would be at the radiator and being blown out the side vents. A lot of the engine seems to be below your legs, actually hanging in the wind. It's a mystery.

  5. #5
    A bozo on the bus deilenberger's Avatar
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    The heat shields go right behind the engine in the triangular areas of the frame. One covers the alternator, the other side replaces the coil cover.

    I found the real answer to K100RT and K75S (less hot - but still hot) heat. A boxer twin. There are no heat problems on my '07 R1200R. I've ridden it in temps up to 100F, and unless I'm stuck in traffic - the heat off the engine really isn't noticeable. It's also MUCH more powerful (torque is your friend) and for me - much better handling (less weight up high.)

    But - that's a major expenditure.

    One or two thoughts - some of the KxxRT's came with rubber boots sealing off the fork tubes to the fairing. These were to keep rain and such from getting up in the under-fairing bits. These were later replaced with scoops designed to catch air as you're moving and guide it up around the instrument cluster. These helped. As did removing the Y shaped center plastic bit that forms part of the holes for the fork tubes. It can be removed by taking out a few screws and reinstalled for winter riding. It makes a MUCH bigger opening in the front of the fairing.

    This all helped a bit - but the RT was still like an oven, so.. I moved on. I wanted to ride not cook.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders
    '12 R1200R - I love this bike!

  6. #6
    Rally Rat
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    Quote Originally Posted by deilenberger View Post
    This all helped a bit - but the RT was still like an oven, so.. I moved on. I wanted to ride not cook.
    With the radiator on the new Wetheads, I wonder if the K-bike heat issue will migrate to the new R's

  7. #7
    Registered User
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    Google JOHNNY BLANKET and K75 HOT LEGS.

    I use a johnny blanket and Baker wind wings. Also insulated the fuel lines and stuffed foam insulation in the spaces where hot air blows in near the lowers. I can ride year round in central TX now.
    Ron

    91 K75RT ABS

  8. #8
    Mars needs women! 35634's Avatar
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    johnny blanket works well http://www.motobrick.com/index.php/t....html#msg20030

    My S only gets sizzling in slooooow traffic or stoplights.


    BMW's rational was probably that only old people would buy an RT, and they always complain about the cold.
    1987 K75S
    Original litter
    Original owner
    2012 Ural Gear Up

  9. #9
    Quote Originally Posted by roncooper View Post
    Google JOHNNY BLANKET and K75 HOT LEGS.
    Interesting, like heat shields on steroids.







    ride what you've got; enjoy the ride!

    Turbo Fluffy Motoclub - IBA 50182 - BMW MOA 69187

  10. #10
    MOA #24991 Pauls1150's Avatar
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    Dunno if the K75 is similar (I'd think so), but a friend installed a little cooler in the fuel return line back to the tank on his K100 - the excess/returned fuel is quite warm (understatement). I forget if it is a power-steering cooler or an automatic transmission cooler, but it's about 2" by 6", and he says it helped a bunch.

  11. #11
    A bozo on the bus deilenberger's Avatar
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    Quote Originally Posted by Pauls1150 View Post
    Dunno if the K75 is similar (I'd think so), but a friend installed a little cooler in the fuel return line back to the tank on his K100 - the excess/returned fuel is quite warm (understatement). I forget if it is a power-steering cooler or an automatic transmission cooler, but it's about 2" by 6", and he says it helped a bunch.
    I'd forgotten how hot the tank could get as the fuel heated up. There is supposed to be foam insulation on the fuel lines under the tank, especially the front one going down to the fuel rail. If that's missing - it can make a sizeable difference in how fast you're cooked since the hot air from the radiator blows right on that fuel line. I also seem to remember seeing once or twice what looked like factory insulation (rubber molded foam) on the actual fuel rail. Same reason. You do have the fuel pressure regulator (and it's lines) right behind the throttle bodies, so some work at insulating them might help.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders
    '12 R1200R - I love this bike!

  12. #12
    Registered User jcj78's Avatar
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    I hacked the fan relay with a switch on the Stormtrooper so I can turn it on as soon as I get rolling. The thermostat takes its sweetass time about kicking the fan on. This way it starts cooling off before it gets so hot. Keeps her reasonable in TN/AL, and I ride in jeans and New Balance's more than I should.
    http://www.motobrick.com/index.php?topic=2337.0

    https://www.google.com/search?q=k75+...F&ved=0CF8QsAQ

    You might also find this interesting.
    http://www.motobrick.com/index.php?topic=5640.0

    She's also pretty naked, so I don't know how much of a difference that makes about being able to shed heat, but I can feel it when I kick the fan on if I'm not geared out. If I'm really irresponsible and riding in shorts, sometimes I'll wait till I hit the 4 lane to cut on the fan so I have a heater. Works pretty good to up around 60-65, which is all I'm good for in such a case.






    edit-
    This might help understand what you're looking at, too, if you are interested in the fan relay switch.
    http://ibmwr.org/ktech/fan-diagnosis.shtml

  13. #13
    RK Ryder
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    For me on my K100RT, the Johnny Blanket made the heat far more noticeable.
    Paul F. Ruffell
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Knights of the Roundel #333

  14. #14
    Quote Originally Posted by jconway607 View Post
    Finally got my K75RT back on the road. Great bike, runs well, but.... the heat on my legs is ridiculous. Exactly like one of the main reasons I sold my R80RT: it was like having two space heaters trained on my lower legs going full blast. I read the posts on this. Apparently it is a well known problem, although BMW engineers seemed to have missed it when they designed and tested the bike. My question: can anything be done to fix this? Can you block off, from inside, the three slots in the long rubber pieces that come up against your legs? Can you do as one person said, get 1 1/2" foam pipe insulation and fit it in around the top of the hollow tube that is that last air chamber near your legs?( the one the rubber pieces fit into) I already have the heat blanket under the tank, and I don't notice a problem under the seat or on the tank. If you block off all this stuff, can it affect the engine cooling? Will removing the lowers solve the problem, but if so, don't you need to fabricate parts to support the main fairing, and the radiator cowling?

    I am mystified how BMW ever sold more than a handful of these bikes, unless it was to Eskimos.
    I'd like to put the guys who designed these bikes on them and make them ride through the Arizona dessert for three days in the summer.
    "Ooh mah God! Deeze deeesiine eezz terreeble! Back to Berlin!"
    Being up here in Edmonton Canada ( home of the Edmonton Eskimos Hockey team) I don't seem to have the problem of the heat.. And since Only vaxed people can leave Canada there's not much chance I'll be riding through any deserts .. LOL.

  15. #15
    Registered User
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    K75RT Heat Control: Is it possible?

    Quote Originally Posted by jconway607 View Post

    I am mystified how BMW ever sold more than a handful of these bikes, unless it was to Eskimos.
    I'd like to put the guys who designed these bikes on them and make them ride through the Arizona dessert for three days in the summer.
    "Ooh mah God! Deeze deeesiine eezz terreeble! Back to Berlin!"
    3 days is not enough!! A month in July is better.

    After trying to keep things cool in the AZ desert for over 50 years, the K bike took some doing. Insulating the fuel lines, bottom of the tank and removing the baffles that direct the heat out the lower fairings helps. But at 112f blowing in your face at speed, a little heat on the legs is kind of a non issue. By removing the baffles it sends the heat under the seat area. It lets a bit more air flow through and makes it a little more bearable. It also sends less heat out the side.
    Also removing the center section of the fairing, under the nose helps too.
    Just an old guy here. Killin' bugs at a rapid pace since '68. Desert dweller.
    Current force: '77 R100/7 ,'85 K100RS-Aug84, '85K100RS-Aug84, '85 K100RS-June85, '93K1100LTSE, '93 K75LTP, '98 R1100GS, '08K1200GT, (2)'72 CB 750s, '76 Honda CB500,

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