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.

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.

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.

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.

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.

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

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.

jimdoyle said:

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.

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These sort of sustained engine speeds create the most heat. An oil cooler is recommended.

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?

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!

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!

lkchris said:

These sort of sustained engine speeds create the most heat. An oil cooler is recommended.

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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

jimdoyle said:

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

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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.

1977 R75/7 said:

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.

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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.

lkchris said:

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.

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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.

Thanks for all of your replies. But how fast is too fast? The question still does not have a definitive answer. I see the red part on the tach. I do know and understand where the redline is. But I'm sure riding just below that line for 24 hours on a 1977 R75/7 is not good for the engine because of the heat created and the pressure on the heads for that duration of time. So in short I'm trying to have my cake and eat it too. Where is safe in speed and/or Rpm? Also I read the IBA website and I believe that proper planning is important but if you do the math you'll still need a certain speed to complete 1500 miles in 24 hours including fuel and eats. At 75 Mph without fuel and eating stops or change of speed limits to be considered it would take 20 hours to complete the BBG. That's why I asked this question. Is it possible to ride faster longer with no damage?
Thanks,
Michael