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Old 03-13-2011, 08:42 PM   #31
squish
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There's a funny thing that happens with collectible stuff.

The less there is of something and the earlier of something, often the higher it's value is.

Look at the Honda CB750 K0 sandcast bikes these in very good nick go for nearly $20k Where as even a later non sandcast or even a K1 goes for much much less.

And some would argue that the later bike is better.


Same deal with the BMW's
The R90S was a special bike when it came out. and it's been special ever since.
The R100S and CS, well they were just another bike in BMW's line up
Nothing really special.

Most if not all people who are buying a R90s today are not buying it for it's performance. They are buying them simply because it is in fact an R90S.
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Old 03-13-2011, 08:56 PM   #32
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Quote:
Originally Posted by Lornce View Post
If you can figure this one out maybe you can tackle why an R80G/S is worth more than an R100GS? While an R100GS is a superior motorcycle in every measureable way.


Well...for this zippy, I will take a R80G/S over a R100GS any day.

Guess which one left me stranded in the middle of freakin' nowhere Australia for 3 days?

I dumped the R100GS for $5000 and bought 2 R80G/S and that started a real love affair that lasted for nigh on a decade and some.

Das Beast is R100RS based, but it is as field strippable as any R80G/S by design. Mine :) Oil bath drive shaft, twin shocks. It will carry a load, and do it zippy fast too. New Battleaxes are not really dual sport spec, but methinks it will get me about anywhere I choose to go.
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Old 03-13-2011, 08:59 PM   #33
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Quote:
Originally Posted by bmwloco View Post
Guess which one lett me stranded in the middle of freakin' nowhere Australia for 3 days?


Yeah, my R100GSPD is down with a wucked driveshaft, too.

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Old 03-14-2011, 02:15 AM   #34
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I've had a 900Z back in days, frame braced with a lot of Godier Geroud braces and a Martin swing arm etc.
Engine (Bored to 1135cc) was fantastic, but my 90S had a much better frame and my 80 G/S a better frame than the 90S !
For me the 80 G/S could be the best bike with a six speed gear box.
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Old 03-14-2011, 07:40 AM   #35
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Quote:
Originally Posted by Lornce View Post
R90S and R100S both ran 9.5:1cr.

R90S was rated at 67hp while R100S was rated at 65hp. 100cc advantage, bigger valves and slightly less power. I think it's fairly well established the power difference was credited to the DellOrto carbs.
R100S was rated at 65hp only for the '77 as I understand -
from '78 - 70hp (40mm headers and ?)
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Old 03-14-2011, 10:01 AM   #36
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The best handling and quickest airhead I've owned was my 1991 R100GS bone stock motor except for a 336 cam....revvy mutha.
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Old 03-14-2011, 11:03 AM   #37
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Quote:
Originally Posted by Rapid Dog View Post
The best handling and quickest airhead I've owned was my 1991 R100GS bone stock motor except for a 336 cam....revvy mutha.
You can't do that! You have to increase the compression! You have to machine the piston's valve cutouts! You have to run steel push rods! You have to put bigger carbs on and modify the exhaust! You have to modify the whole engine since one thing effects another! The 336 is a duration cam that has no bottom end and midrange! It won't idle below 2000rpm! They are just no good unless you are building a race bike for long, open courses!

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Old 03-14-2011, 01:01 PM   #38
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I had a 1974 CB750K, a 75 CB750 F1, and a 77 CB750 F2. I'm pretty sure the F series stock was faster than the R90 (didn't handle as well for sure) and the K model (I thought) would pull the BMW in a drag race, but mine (and everybody else that I knew) had a Kerker 4-1 and rejetted carbs which made a big difference.
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Old 03-14-2011, 02:41 PM   #39
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I forgot that the F came out in '75. I think you are right in that they probably would outrun a R90S. They run a lot stronger than a single cam. Besides the Elsinore, the F was the first Honda that ever impressed me much. They still weighed a ton. Up until the 900RR, I can't think of a Honda besides the Elsinores that didn't weigh a ton?

I was just thinking, the first Japanese four stroke street bike that ever caught my attention was the GSXR. Mostly because they didn't weigh a ton! At least at first!

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Old 03-14-2011, 02:56 PM   #40
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R90S Information/R80GS Information/Highest Airhead Horsepower

Responding to several emails in this thread:

The highest horsepower airhead BMW ever produced for the
US market was the '77 R100S and R100RS as they had 40 mm exhaust pipes. You can tell if a bike has 40 mm pipes and heads by looking closely at the exhaust clamp that connects the header to the muffler; if it is stamped with a 42, it is for a 40 mm pipe, however if it is stamped with a 40 mm it is connecting a 38 mm pipe.

These 40 mm US '77 bikes had 70 horsepower, the highest of any airhead produced for the US market.

BMW continued to produce 40 mm piped bikes for other markets after '77, just not for the US.

The R90S was rated at 67 horsepower.


The R90S model was a big first for BMW in many ways; first 900 cc engine, first disc braked bike, first smoked paint, it was designed by a designer, not engineers, and had a great many designer parts. For appearance sake, it did not have front fender stays, the '74s had the ribbing on the front cover polished, there were several chromed nuts and bolts, including the lower right shock bolt being a chromed acorn nut, at least in initial production. The speedo and tack had a white surround in the instruements for '74, the fairing was the first one for BMW as was the seat cowling, the clock and volt meter was a first, first exposed forks (for looks), it was the only BMW to have Dell'Orto carbs, the list goes on.

FYI all R90Ss are entirely painted silver and then either the TT Silver Smoke is made by adding a smoke color that has brown and green in the paint; it is not black. The Daytona Orange color is made by adding the orange color.

The smoke color is added by controlled over spray, not air brushing.

The TT in TT Silver Smoke stood for the Isle of Mann "Tourist Trophy" races.

BMW employees referred to the Daytona Orange color as "egg yolk" as it was not well received

I started an internet discussion group for the R90S model that is entitled "R90sWorldnet"; a Google search will bring you to it. There are almost 1100 R90S enthusiasts on this list from all over the world and it is a fabulous resource for all things "R90S". Come join us if you wish.

I helped write the book "BMW R90S" by Ian Falloon, it is still available and in production. I was fortunate to be pictured on the front cover of this book. If you like the R90S model it is worth buying. My R90Ss are pictured throughout this book.
I completely restored an R90S about 2 years ago and put 10,000 miles on it last year.

The Daytona Orange color was named after the races in Daytona Beach, Florida and the color was meant to mimic the sun rising at Daytona Beach.

BMW won the first Superbike races for '76 with the R90S, with Reg Pridmore at the helm. The first race at Daytona in '76 was won by Steve Mclaughlin as Steve drafted by Reg and won by a smidgen; at first Reg was declared the winner but a check of the photo as they were crossing the finish line showed Steve had won.

The R90S was produced for only 3 model years, '74, '75 and '76 for total production of about 17,300 units.

If you know your car history you have likely heard of Bob Lutz. He is a car enthusiast's enthusiast. About 1973 he worked for BMW and the R90S had been designed but not released for sale to the public, as many at BMW did not think the R90S should be released as it was too radical. Bob Lutz convinced BMW management to release the R90S for sale, and for this reason he is considered to be the father of the R90S model. Bob retired for about the 5th time just last year as a VP for GM. He is very popular.

A very nice '74 R90S sold on eBay last night, 3/13/11 for about $12,300 which is a very good price for such a nice machine as that one was. The highest price I have seen paid for an R90S was just under $25,000 a few years ago at an auction, and several have sold in the range of $18 to $20K but they had extremely low miles, such as less than 200 miles.

The R80GS is such a popular model due to it's overall solid performance and it will not trash its driveshaft as the R100GS will. The R80GS is also lower in seat height than the R100GS. All you have to do to make an R80GS reliable is to add an aftermarket diode board and higher output alternator such as from Motorrad Electrik. They are true cult bikes and a good one will bring upward of $8000 and more.

I also helped Bill Stermer with pictures of my R100RSs and information for the book "BMW R100RS".

Thanks for reading

If anyone wants to "talk R90S", email me at drbeemer@snip.net

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Old 03-14-2011, 03:17 PM   #41
bmwloco
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20 years ago, I wanted an R90S bad... real bad.

My R75/7 had and "S" faring and gauges. Two into one Luftmeister pipe. I wanted it to be an R90S.

Fast forward to now... if I could find a bog stock R75/7 in reasonable shape, I would buy it before an R90S.
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Old 03-14-2011, 03:49 PM   #42
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Quote:
Originally Posted by drbeemer View Post

FYI all R90Ss are entirely painted silver and then either the TT Silver Smoke is made by adding a smoke color that has brown and green in the paint; it is not black. The Daytona Orange color is made by adding the orange color.

If you know your car history you have likely heard of Bob Lutz. He is a car enthusiast's enthusiast. About 1973 he worked for BMW and the R90S had been designed but not released for sale to the public, as many at BMW did not think the R90S should be released as it was too radical. Bob Lutz convinced BMW management to release the R90S for sale, and for this reason he is considered to be the father of the R90S model. Bob retired for about the 5th time just last year as a VP for GM. He is very popular.
Mac Kirkpatrick
Mac -

That was a treat. Thanks for sharing. The similarities between the TT Silver Smoke and Daytona Orange make so much sense now but I had never put 2 + 2 together before.

The story about Bob Lutz is a big surprise. I just assumed that he was always a GM lug (although a charismatic and visionary lug ).

Do you know if any 40mm R100S exhausts were delivered as 78 models? I know my 78S had 40 mm carbs and thought it had 40 mm pipes but it's been over 20 years. Regardless, I loved that red smoke bike.

Cheers.
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Old 03-14-2011, 06:28 PM   #43
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Quote:
Originally Posted by drbeemer View Post
The highest horsepower airhead BMW ever produced for the
US market was the '77 R100S and R100RS as they had 40 mm exhaust pipes.
Mac Kirkpatrick

BMW never sold an R100S with 40mm exhaust pipes in the North American market. Not sure they sold one in Europe, either, but I could be wrong about that.

North American R100S's had 38mm exhausts while a lot of early '77 R100RS's were fitted with 40mm exhausts.
R100S rated at 65hp R100RS rated at 70hp.

fwiw,
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Old 03-14-2011, 07:19 PM   #44
supershaft
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I was thinking that the R100S had 9.0:1. I would trust what an owner's manual says. If the compression is the same, isn't the only difference between a RS and a S is the headers. 5hp at the crank? I wonder what got the '78 S googled hp up to 70 while the '77 S googles at 65? It couldn't have been the advanced cam timing or the 2mm larger headers since it didn't have them. Sorry, I have never payed much attention to the claimed hp ratings since I think they pulled all of them out of their ass. They are good for comparison in some cases IMO and BMW doesn't exaggerate the figures near as much as most companies but . . . .
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Old 03-14-2011, 09:07 PM   #45
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I never pay much attention to the HP figures either. As a matter of fact, the HP figures seem really low for the kind of power delivered.

Another difference you've got to take into account between later RSs and the 90/100S besides exhaust and dellortos/bings is the final drive ratio. The later RSs have a 32/11 whereas the Ss had a step lower at 33/11.

But I totally agree - there's very little difference between a 90S and the 100S. They're both great, love the paint on them all, but lean just ever so slightly toward the smoke red as my favorite.
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