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Thread: How fast is too fast?

  1. #1
    Registered User R75_7's Avatar
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    How fast is too fast?

    A couple of weeks ago I was riding my R75/7 at 75mph and 5000rpm for a little over 1000 miles. Is that a safe speed for the bike? Am I over revving the engine or can I give it more?
    I would like to do a Bun Burner Gold, but if I can't ride faster I'm afraid I won't make it.
    Thanks.

  2. #2
    Blocking the slow lane
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    Assuming most of the basic mechanicals are in good shape, there's no reason you can't run it up there all day. The bigger problem on a BBG is going to be the fuel stops you are going to have to make every 125-150 miles from riding WFO.
    Jon Diaz
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    BMWMOA Ambassador

  3. #3
    Registered User R75_7's Avatar
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    Thanks for the quick reply. What is WFO? I think I can get about 200 miles a tank but when riding long distances I stop between 150 and 200 miles due to limited fuel sources. Also when I'm passing on the Interstate and there may be people behind I kick it up a little. Is it safe on the bike to exceed 5000rpm? Thanks.

  4. #4
    Blocking the slow lane
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    WFO is how we small bike people have to ride with the big bike folks.....Wide F*cking Open.

    I would not worry about cruising beyond 5000rpm for days on end unless the air temp was very hot. And even then I wouldn't worry that much.
    Jon Diaz
    BMW K75/K12GT
    BMWMOA Ambassador

  5. #5
    riding the bike(s) grasslander's Avatar
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    Safe for the bike? Heck yes. At RPM, Oil pressure is up and air flow around the heads is up. Do it all day, just check the oil every 1500mi or so.
    Jim Doyle
    Expert M/C road racer and crew chief
    Owner G-Baby Racing endurance team
    2013 ASRA/AMA Team Challenge GTL National Champions

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    Registered User PeoriaMac's Avatar
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    gunning the R75

    Depending on loading/saddlebags etc, you may get some instability around 85. I do, anyway. Of course, you could always scout around for a Heinrich and other larger tank...or go the fuel cell route.
    As always, YMMV.
    Mac
    Mac
    1986 R80RT, 2005 R1200GS
    Livin' Large On The Lake

  7. #7
    Loose Cannon flash412's Avatar
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    Do you see the area on your tachometer painted red? That is the no-no zone. Stay out of there and you can run the full distance between oil changes without any problems whatsoever. In Europe, it is easy to ride 100 miles in an hour on the autobahn. That is precisely where these bikes were designed to do what they do. I run WFO for long distances. There's a whole lot of nothing in Wyoming which is not far from where I live.

  8. #8
    Registered User lkchris's Avatar
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    Originally posted by jimdoyle
    Safe for the bike? Heck yes. At RPM, Oil pressure is up and air flow around the heads is up. Do it all day, just check the oil every 1500mi or so.
    These sort of sustained engine speeds create the most heat. An oil cooler is recommended.
    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

  9. #9
    Has the GS-Lust The_Veg's Avatar
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    Since we're on the subject then, what would be a too-low RPM to cruise at? Am I correct to presume that the Airhead engine is pretty much okay as long as it's not lugging?

  10. #10
    Registered User R75_7's Avatar
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    Veg,
    I cn only speak for my own bike. I usually shift up between 3800rpm and 5000rpm. I shift down at around 3500rpm. When I'm shifting up I've got more time and a larger cushion in front, so I can pay more attention to the rpms. When I shift down I go by sound because I live in L.A.,lots of traffic, and I usually don't have the luxury of looking too carefully at the tach. I got those numbers from some threads I've read in the past and what fellow riders have told me then used them as guidelines and played it by ear and how it felt as far as the strength of the pulling power and the wind of the engine. The problem with not having any owners manual(and it's my first BMW) is that it's all opinion or heresay and nothing concrete from the people that built the machine. I hope I helped you(and didn't put you to sleep). Also congradulations on your new purchase. It looks really beautiful!

  11. #11
    Has the GS-Lust The_Veg's Avatar
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    Thanks R75, that's actually pretty close to what I've been doing. I pretty much go by the sound and feel of it- keeping it in the ranges in which it sounds "happiest." I'm stumped to define that, but it seems to work really well anyway.
    And thanks for the compliment on the bike too!

  12. #12
    riding the bike(s) grasslander's Avatar
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    Originally posted by lkchris
    These sort of sustained engine speeds create the most heat. An oil cooler is recommended.
    Actually, lugging around at 2500 RPM, 2 up, with a full load of gear or setting in bumper to bumper trafiic creates the most heat. I remember BMW told me that the only reason my old '90 R100GSPD had an oil cooler was for low speed offroad conditions.

    JD, 25646
    Jim Doyle
    Expert M/C road racer and crew chief
    Owner G-Baby Racing endurance team
    2013 ASRA/AMA Team Challenge GTL National Champions

  13. #13
    Registered User lkchris's Avatar
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    Originally posted by jimdoyle
    Actually, lugging around at 2500 RPM, 2 up, with a full load of gear or setting in bumper to bumper trafiic creates the most heat. I remember BMW told me that the only reason my old '90 R100GSPD had an oil cooler was for low speed offroad conditions.

    JD, 25646
    Sorry, heat produced is directly proportional to fuel burned. The higher the rpm, the more fuel burned for a given time. GS are bikes more likely to be run at sustained high rpm in lower gears.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  14. #14
    dlearl476
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    Re: How fast is too fast?

    Originally posted by 1977 R75/7
    I would like to do a Bun Burner Gold, but if I can't ride faster I'm afraid I won't make it.
    Thanks.
    A quick trip around the IBA website will net you this little gem of knowledge: "It's not how fast you go, it's how little time you spend stopped that matters". Planning is everthing.

    "Sorry, heat produced is directly proportional to fuel burned. The higher the rpm, the more fuel burned for a given time. GS are bikes more likely to be run at sustained high rpm in lower gears".

    Kent, might I ask where you came by this information. I buy the "directly proportional...." bit, but many years of experience in vehicles with GAUGES instead of idiot lights has taught me that the quickest way to overheat a vehicle, especially an aircooled one, is to attempt a grade or to pull a load at too low an RPM. In MY experience, motors run coolest ~75% of their max torque, regardless of speed. For example, my F650 gets hot off road when the airflow is poor and I'm expecting it to pull around in 1st gear at 2000-2500rpm. It also gets hot (250+)above 5K, but will cruise all day at 4.8K and never get above 200 degrees. My '72 2002 would overheat going up I-70 to Vail at 3500 rpm in 4th, and cool right down at 5200 rpm in 3rd.

  15. #15
    riding the bike(s) grasslander's Avatar
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    Originally posted by lkchris
    Sorry, heat produced is directly proportional to fuel burned. The higher the rpm, the more fuel burned for a given time. GS are bikes more likely to be run at sustained high rpm in lower gears.
    I will also buy "directly proportional". But it's really about heat management.

    High RPM + low speed = hot engine.
    Lugging (load + low RPM) = hot engine.
    Over idle = hot engine.

    The first 2 situations tie back to "dp"
    The third to a heat management issue. All three can be minimized with heat management techniques.

    It's an air cooled motor with some cooling from oil lubing.
    No airflow = high head, cylinder, and oil temp. At 75 MPH you have outstanding AIRFLOW (cooling).

    In the GS example BMW addressed low speed operation, to some degree, with a basic non-thermostat oil cooler. At higher RPM you have excellent airflow to transport heat away. This is why on all of my airheads I can can run at speed, sustained, and be able to hold my hand on the valve covers without discomfort. Heck, my 77R100RS did 1150 August miles in a 16 hour stretch around the Kansas 4 corners in the mid '80s. Didn't even need any oil added + it got 46 MPG.

    Properly loaded, driven, maintained, it'll go all day at speed by design.
    Jim Doyle
    Expert M/C road racer and crew chief
    Owner G-Baby Racing endurance team
    2013 ASRA/AMA Team Challenge GTL National Champions

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