Airhead on the Interstate

[bc1100s]

I recommend an "Italian Tune Up". A tried and true method of blowing out any carbon built up from years of meekly shying away from any confrontations with an S .

Step 1. Make sure bike is warmed up properly.
Step 2. Find lightly travelled interstate with straight-access on ramp.
Step 3. Accelerate briskly (WFO) to redline in every gear.
Result: A fine running machine.

Disclaimer: Launched con rods and floating valves are not the responsibility of this poster.

 

[69ZEFF65]

I remember the /2 rally runs up I 75

Down here in the Florida flats (all of Florida) we used to have rallies four or five times a year. We would leave Naples at about 3 pm and a lot of times we would run up I 75 just to get there and crack a beer before dark. The one thing about the /2's I ride is they don't have a tachometer, so you have to rely on a clackometer (first Rev limiter on a bike). If the valves float they will clack so back off on the throttle a little. Despite all the hard running up the interstate to & from rallies and other adventures I never had the clackometer (first rev limiter on a bike) kick in and advise me to back off. I still take the /2's out for a good ringing out to keep them fresh and I still run them up to Wide F-ing open and hold it but still no Clackometer, at this point in time I think a tach would scare me into not riding and enjoying my old German boxers. I gearing up to unleash several freshened up /5's and 6's from my stable and have thought about disconnecting the tach just to relive the shift by clackometer and audible rev limiter feature I have gotten used to.

 

[AntonLargiader]

The first R75/5 bikes came with a 2.91 (32/11) final drive. Mine early bike has this, and 70 MPH is something like 4400 RPM. The 2.91 makes 1st gear a pretty tall pull-away gear.

Later (maybe for MY71 or even during the MY70 production) they switched to a 3.20, which is a pretty big change (3 steps). Nearly all of the bikes I see have the 3.20. That explains about 10% difference in speed or RPM.

I tell you, that 2.91 is wonderful on the highway because the engine is really in a sweet spot. You pay for it by feeling like there is a pretty big gap between gears, though, The 4-speed is that way naturally but the taller FD accentuates the feeling. I also have a 5-speed in mine, but with the tall FD I find that I hardly ever use 5th.

 

[bluehole]

I recommend an "Italian Tune Up". A tried and true method of blowing out any carbon built up from years of meekly shying away from any confrontations with an S

Is there no haven from these crazy S riders?


Anton, interesting information. Thanks.

 

[james.a]

If you do not run low on oil, you can't hardly hurt an R75. I rode my 1973 R75/5 from Peoria IL to Minneapolis for the rally a few years back, on the interstate, wide open, as fast as it would go. No injury. It still runs great to this day and I expect it to for a very long time. It has been in my garage since 1989, and it will be the very last thing to leave.

 

[8ninety8]

Can't ride my S wide open in high gear, the speed scares me. Wide open in third is as far as I'll go.

Got pulled over many years ago coming over a bridge. Said I was going 65. I said impossible I was still in second!

IIRC, a 3.00/1 rear gear with standard rubber will yield 16.8 mph per 1000rpm in high gear. So calibrated speedo should show around 67 mph at 4K. 4.5 K, 75 mph, and so forth. Gotta know the ratios, don't know what other gears will pull, but a good math person could figure it out quickly.

 

[DonTom]

The R75/5 feels busy on the interstate.

You can ride it all day 6,000 RPMs without any problem. Sometimes I am at WOT for a long time on mine, which is usually in the 90's (as shown on a GPS). I have a habit of riding my 71 BMW R/75/5 rather hard. Nevada deserts with no traffic makes me do it.

IMO, the airheads don't like to be babied! Ride it and ride it hard!

-Don- Reno, NV

 

[DonTom]

I still have my original 1971 R/75/5 Owner's Manual. Still like new.

Page 56, "Technical Data".

Maximum RPM: 7,000
Permissible Cruising: 6,300 RPM (6500 on the R50/5 and R60/5).

So BMW says you can ride it all day and all night at a continuous 6,300 RPMs.

That is if it's yet broken in!

-Don- Reno, NV

 

[SCBuckeye]

1978 r100/7

My 1978 R100/7's "buzzy" range (as was my R90 before it) is from around 3,750 to 4,100 RPMs. At 5,000 it runs so smooth and quiet, almost to the point that I forget I am on it. Seems like it could go on like that all day. I wish I could say the same for me!

BTW, In my opinion, I would never run my bike up to redline on acceleration.

I do like cruising around 65 to 70 MPH.

 

[willhawks]

My 1 1/2 cents worth...

1. Listen to Paul Glaves and Matt Parkerhouse
2. Valves, Timing, Carbs (dead dirty last)
3. Having completed these steps, start by realizing that the boxer engine shares it's basic design with light aircraft engines
4. Said engines are designed to run at high speed for long distances
5. The concept of efficiency comes into play here, ergo efficiency = highest speed @ the best fuel consumption
6. Very often this setting is found to be 70% power
7. If memory serves, your redline is 7300 rpm
8. Ergo, 70% power for your engine is 5000-5100 rpm
9. Your engine produces it's maximum torque (43.4 ft lbs) @ 5000 rpm
10. This corresponds roughly with the 70% power setting for light aircraft.
11. Finally, in the words of the Late Great Keith Patchett (MOA#981); "Spin it or you'll fix it"

Best,

W.

 

[lmo1131]

If by "busy" you mean "squirrel-y" it may be because your '72 has a SWB (short wheel base) chassis. If is has any kind of fairing on it that is probably contributing to the sensation as well. Apply damper if you have it.

Pushing 80-85 (which is VERY seldom) my '73 LWB is solid with the steering damper slightly snugged. I've run the bike nekkid for the last fifteen years but it ran with the full Vetter load from '75 until then. Before the Windjammer it had a Bates windshield on it and never seemed to know the difference stability-wise.

And if this isn't what you mean by "busy"... never mind.

 

[bluehole]

I should have been more clear. She feels like she is revving pretty high. Based on the responses, I think the problem is me being used to riding an Oilhead on the interstate. I think I need to get used to running the Airhead on the interstate. Hope to get a few high speed miles in tomorrow.

 

[bob_m]

Just because she is breathing hard doesn't mean she is out of breath.

 

[dennisdarrow]

If by "busy" you mean "squirrel-y" it may be because your '72 has a SWB (short wheel base) chassis. If is has any kind of fairing on it that is probably contributing to the sensation as well. Apply damper if you have it.

Wait till you go into the infamous high speed wobble if you think just cruising along at 80+ is squirrely. lol.....after you clean your shorts you begin to wonder if you really need to do this 80+ stuff or not.......

It's real that this happens and spooky as can be. For me, my 72 had an Avon fairing and I had just put on Dunlop K81's if I remember right.....Duane Asherman discusses this and his cure for it back in the day.....Worth checking out if you plan on keeping this oh so fine machine and riding it hard and fast.........lol....is there any other way on these sweet machines at that speed:??....God bless....Dennis

 

[bluehole]

Over an hour at interstate speeds yesterday. There is indeed a sweet spot around 5,000 rpm. Thanks guys.

 

[lmo1131]

Just curious, why are you driving on the Interstate with the "parking" light on?

 

[james.a]

Just curious, why are you driving on the Interstate with the "parking" light on?

I was kinda wondering about that myself.

 

[barryg]

On my '71 R50/5, I run a halogen parking light bulb. I think it's bright enough to pass as a light in the daytime. It helps the marginal charging system. Anyway that's my story and I'm sticking to it.

 

[bikerfish1100]

i know it's not an exact comparison, but the motors were essentially the same...

the Owner's Manual for my '78 RS indicated "max top speed 7500 rpm", and "max sustained top speed 7250 rpm."

i wouldn't worry about it.

 

[lmo1131]

It helps the marginal charging system.

I, too, run the 4W parking light on when in town, but out on the freeway, it's 55W H4 the whole way (converted to H4); once I got the voltage regulator situation sorted out and back to 14.1 volts I don't have any problems.