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Old 03-13-2011, 12:16 PM   #16
supershaft
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I don't think it is too objective at all to say that if you put Dellorto carbs on a R100S you have got a bike that is at least a little bit better than a R90s in so many aspects. A lot of the R90S's performance gains came from those carbs. The same thing can be had again and on top the stock R100S IF they had the same carbs as a R90S. Put dell's on the R100S and the contest is over IMO. Especially if you are comparing '74's to '77's. I think the R90S has a bit higher CR than the R100S? I know the R90S has a lot smaller ports. If the compression is higher, that comparatively probably helps lower rpm power more along with the smaller ports. I suspect many riders that never rev their engines much mike like the smaller ports/higher CR combo? But then again, nothing helps power across the board like more cubic centimeters.
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Old 03-13-2011, 12:24 PM   #17
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Quote:
Originally Posted by supershaft View Post
I don't think it is too objective at all to say that if you put Dellorto carbs on a R100S you have got a bike that is at least a little bit better than a R90s in so many aspects. A lot of the R90S's performance gains came from those carbs. The same thing can be had again and on top the stock R100S IF they had the same carbs as a R90S. Put dell's on the R100S and the contest is over IMO. Especially if you are comparing '74's to '77's. I think the R90S has a bit higher CR than the R100S? I know the R90S has a lot smaller ports. If the compression is higher, that comparatively probably helps lower rpm power more along with the smaller ports. I suspect many riders that never rev their engines much mike like the smaller ports/higher CR combo? But then again, nothing helps power across the board like more cubic centimeters.
Is the R100S also not the large valve engine? I think the Bings on the R100S are 40mm and while maybe were not as responsive as Delortos they sucked more air?
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Old 03-13-2011, 12:51 PM   #18
supershaft
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Big port heads have bigger intake valves as well. 44mm versus 42mm. They also have much larger ports. Most people call them big valve heads versus small valve heads. I call them big port heads versus small port heads. Why? Because it is very easy to put 44mm valves in in small valve heads AND they work very well. IMO, the main difference in the heads is not the size of the intake valves but rather the size of the ports!

Sure the 40mm bings flow more air than the 32mm Bings but the Dellorto's are much better performing carbs in almost every performance aspect. I think it is safe to say that the 40mm Bings just get you more of what the 32mm Bings are. Many, many tuners do not like where that takes them.

supershaft screwed with this post 03-13-2011 at 12:57 PM
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Old 03-13-2011, 01:59 PM   #19
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Originally Posted by chazbird View Post
No pictures of this, so I guess it doesn't exist on the internet, but my friend who has his own shop I've been going to for 20+ years is a real air-header and over the years has had many of them. About 4 years ago he finished a little over a year build of a R90S entirely from NOS BMW parts. The only thing that wasn't from Germany were replica new Bing carbs from Poland, although they may actually be licensed from BMW, I 'dunno. He sourced the parts from his friend who owns a BMW dealership; interesting you can still get all this stuff. He wouldn't admit to saying how much more than 15k he had in it. Its smoke gray, and obviously it came out perfect. It now has about 20,000 miles on it.

???????
Bings?
Why is it "obviously" perfect?
Pictures, or the factor is gonna get deeper and deeper around here
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Old 03-13-2011, 02:19 PM   #20
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And I really liked the way his post started off. That had me laughing.
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Old 03-13-2011, 02:26 PM   #21
Caddy82rats
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I've got a 74 90S All engine rebuild, brand new Dell.
My 77RS doesn't accelerat as hard as the RS
My old 79RS with 82 fly whell and 40 mm Dell was accelerating harder than the 90S
All this 3 bikes had 9,5 CR

So : 100 and 90S accelerate praticly the same and you can't compare driving feeling from CV carbs to bing, thats for me the main difference.

In 74 90S was one of the best bikes, if you compare it to a 84 R100S, it's a non sense for me.
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Old 03-13-2011, 05:56 PM   #22
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A good friend of mine ordered an R90S in Baton Rouge, La. He said the one he got was the made for Europe model with a different cam.
I think it was the 1974 model, silver smoke.

Years later I bought it from him and experienced the "kick in the butt" as it accelerated over 85mph! He said it was the different "cam."

Had that bike for years! Sold it to my brother in law for what it originally cost...about $3400.

I've had a lot of memorable bikes: 69 Triumph Tiger 650, Norton 850 Commando, BMW R/75, Honda 350 4 cylinder, Kawasaki ZRZ 1100 Eddie Lawson, Honda 1300 VTX, and finally, the Yamaha FZ1.

None of these bikes has inspired the pride of ownership and confidence of that old R90S. Put some Craven Arrow bags and full Avon fairing on it and went to Canada several times....from Louisiana. I popped a clutch cable in the Okenagan Valley....total problem with the bike!

Nostalgia is a great thing!
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Old 03-13-2011, 06:18 PM   #23
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Originally Posted by SDVET View Post
Ok all you historians, why is the 74 thru 76 R90s held in so much higher esteem than the 77, 78 R100S models? How do the two bikes compare in performance. A nice 90S seems to bring about twice the dollars as later models.
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.


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Old 03-13-2011, 06:30 PM   #24
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Nothing else was faster?

... I'm pretty sure that the Kawasaki 750 triple, 903Z1, and CB750 Honda were faster...
Agree on the Z1.

But I know a CB 750 wasn't faster than an R90S.

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Old 03-13-2011, 07:02 PM   #25
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Originally Posted by macbethandbanquo View Post
went to Canada several times....from Louisiana. I popped a clutch cable in the Okenagan Valley....
Louisiana to Canada via the Okanagan Valley in WA/BC? It sounds like you took the scenic route.
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Old 03-13-2011, 07:06 PM   #26
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Quote:
Originally Posted by supershaft View Post
I don't think it is too objective at all to say that if you put Dellorto carbs on a R100S you have got a bike that is at least a little bit better than a R90s in so many aspects. A lot of the R90S's performance gains came from those carbs. The same thing can be had again and on top the stock R100S IF they had the same carbs as a R90S. Put dell's on the R100S and the contest is over IMO. Especially if you are comparing '74's to '77's. I think the R90S has a bit higher CR than the R100S? I know the R90S has a lot smaller ports. If the compression is higher, that comparatively probably helps lower rpm power more along with the smaller ports. I suspect many riders that never rev their engines much mike like the smaller ports/higher CR combo? But then again, nothing helps power across the board like more cubic centimeters.
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.




















I still think a smoke red '78 R100S looks better.








Butler & Smith add from '78 (and the valve cover's are mixed up).
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Old 03-13-2011, 07:13 PM   #27
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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.


Not everyone considers bigger and heavier better.

I agree with you about CB750's. Some will say Guzzi's were faster. Ducati's were faster. Laverda's were faster. I wonder if MV's were? I suspect so. I think some would say a Commando is faster, at least for a while! Any other arguable suspects?
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Old 03-13-2011, 07:17 PM   #28
fishkens
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Originally Posted by Lornce View Post
Butler & Smith add from '78 (and the valve cover's are mixed up).
he he, even they got 'em backwards. Kinda like on the '88 GS when the ad showed the front fender in a low position that would have the tail catch the tire and roll up under itself.

p.s. I like the red smoke best too.
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Old 03-13-2011, 07:19 PM   #29
supershaft
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We had to rotate those smoke red R100S's so that all the sides got equal sunlight from the windows or one side would fade to a different color if we didn't sell them quick.
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Old 03-13-2011, 07:28 PM   #30
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Originally Posted by supershaft View Post
Not everyone considers bigger and heavier better.

I agree with you about CB750's. Some will say Guzzi's were faster. Ducati's were faster. Laverda's were faster. I wonder if MV's were? I suspect so. I think some would say a Commando is faster, at least for a while! Any other arguable suspects?
Norton Commando? Don't think so. Could prolly blow it up pretty good trying, though.

'76 Mk1 LeMans? Be pretty close.

'75 Ducati 900SS? Pretty even there, too. Unless it was ordered with optional and completely street illegal 40mm Dells and Conti megs. As most were.

Laverda's Jota (which was faster) didn't arrive until '78 iirc, while the pre-Jota Laverda 1000 3C was not faster than an R90S.

MV's street offerings were rare as hen's teeth and I don't think they were tuned very highly. Don't know for sure.

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