So I have a question for you guys. I have one of the original R100RS bikes, a 1977 model year built in November 1976: Silver Blue, 40mm, pinstriped wire wheels etc. Supposedly there were only around a thousand produced for the US market, mine's 6180272 which I think makes it the 272nd R100RS shipped to the US. I'm the second owner, I got it through a friend who knew the original owner who got rid of it for health reasons. Basically he couldn't ride so he offered it to my friend (a Harley guy) who in turn offered it to me (a BMW guy). Though I never met him the previous owner claimed it was all original, just as he got it new. I certainly looks all original, except for one thing, it has dual plug heads. I've heard that these original bikes had a higher compression and needed the second plug in order to deal with lesser quality US fuel. My question is was that an option direct from BMW, that was done before it was shipped, or was it done here in the US and if so by whom?
probably done by the dealer or some other shop. as far as I know, no airhead ever came from the factory with dual plugged heads.
Here's a link to lots of great airhead stuff, including period correct accessories (farkles of the day). Cannot see anything that looks like dual plugs, nor can I see anything in the 1976-1977 text that indicates that dual plugging was an option. Ignore the date in the URL. Click any of the pages to enlarge: http://www.omnilex.com/public/bmw78/ Lots to read BTW- you are correct, best I can tell, with your build date information, according to :http://bmbikes.co.uk/chassispages/enginechassis1000.htm
I also have a 77 RS. I didn't know anything about the 77 being special when I bought the bike - I just wanted a project bike. I had a photo of the bike on my laptop as the desktop image and a colleague saw the picture. He was quite interested and told me a lot about the 77RS. Subsequently, I discovered the registry for the 77RS and "met" the owner of the bike assembled next to mine at the factory -seems like a lot of the 77RS bikes are still going strong. Of course, I had to get the obligatory 77RS coffee cup - other 77RS do-dads are also available. See links below - http://www.ibmwr.org/rs77/ http://www.cafepress.com/rs77 My 77RS after a bit of a re-do
I do wish BMW HAD produced dual plugged airheads. That would have been a huge step in the right direction!
Dual plugging airheads started in the US around the time that unleaded gas was introduced and high test gas got more difficult to obtain, the idea was to help high compression airheads run unleaded without pinging. This was never a factory option and I agree with SS that if BMW had gone down the dual plugging route BMW could have maintained the power of airheads into the 80s rather than gradually detuning them. The lower spark plugs on your bike might well have a smaller diameter and or shorter thread length than the standard upper plugs, better not to mix them up. The ignition timing will be different from stock. At full advance you should be looking for 28 degrees, rather than the stock 32 degrees. Timing at tickover should be the same as stock. If your bike uses the original points plate, it may have been adapted to give you this timing. If this is not done properly then you won't get the best results from your dual plugging. Today you can buy various a types of aftermarket electronic ignitions that have the correct ignition curve for your engine. Good luck with the bike, it is a classic and keeping it stock will maintain its status and value.
I went down the dual plug route a few years ago. I couldn't see any benefit to it at all and spent hours messing with bean cans and different ignitions to try and see an improvement. I gave up in the end and just put the standard ignition back in and sold it.
Had a friend who bought a new one when they came out here in UK. ...to sit alongside his 90/S and 90/6 ( yes he had a few $$$$ )...and I am 99.9% certain..only single plug heads ....as I looked at purchasing one also at the time I bought a CBX 1000/6 instead ...
BMW did not dual plug heads of any Airhead engine, ever. Dual plugging is an improvement on the original design. It works better than the way BMW built it. You can't have this both ways. It's either how BMW did it or it's the way it should have been built. It is never both.
I avoided it for years and now wish I had done it a long time ago. Of course, I didn't just dual plug my heads. I went from 8.5:1 pistons to 9.5:1 pistons and had .025" milled off the heads. I spent about ten minutes remapping my advance curve in my bean can and about an hour neatly installing and wiring my .7 ohm Dyna coils with BMW /2 bulk solid woven copper spark plug wire and 5k NGK caps. That and hours and hours of reshaping my ports, going up from 42 to 44mm intakes valves, and installing custom made 4130 push rods made a huge difference. The thing was already running pretty good and now it hauls with big gains all through the rev range with the biggest gains in midrange power! Except for moorespeed, most all airhead tuners and tuners of many other types of two valve hemi head engines dual plug for performance. For instance, for decades now all competitive HD XR750's are dual plugged that I have seen. Same story with top fuel dragsters. The list can go on and on. Why? It works!
Besides no pinstripes, the silver doesn't "look right"-- the RS sliver had a bluish tone. ANd BMW never used capnuts on the front fender-- only M6 Nylocs. Not to throw off on the ole girl-- she just ain't as untouched as she says. :huh She's been around the block a couple of times. --Bill
Thanks for that. I've been lurking here for years and have always appreciated the intelligent info people bring to the site, but it's great to experience it first hand. There's things there I knew and things I've not considered, and I always love learning new things. Well Wild Bill, you're making me blush. With 46K she aint no virgin but It don't dissuade me in the least Don't let the pic fool you, the bike is the standard Saintly 530 blue. That pic and my studio lighting just makes the blue look more silver then it is. The pinstripes are a darker blue, and it's striped on the tank, seat, fairing and both rims but oddly not on the front fender. I suppose this means that the front fenders been replaced or repainted but if it was they did a perfect job as it an exact paint match and flawless. You know there is stock and STOCK The owner said it was all original just as he bought it but he bought it from a dealer out here. I suppose the question is how original was it then. There are several things that are slightly different, dual pugs, some stainless hardware, the clock surrounds are black not silver, the windscreen has a smoke tint to it, the rear shocks are blue and black the rear fender and battery covers are blue.. Perhaps some of these things were options offered by BMW, perhaps some of them were options offered by the dealer that sold him the bike. There are other little things too. Take the tank for instance. Ignore the fact that the lighting makes the blue a little more silver, it's actually the right color what's interesting is the pin-striping. maybe it's just aged but it is definitely darker and finer the most of the pin-striping I've seen in other R100RS pictures. Fro instance look at this bike that is supposedly almost 99% original. That pin-striping is not only lighter in color it's also much fatter at the bottom at the tank. All the pin-striping on my bike is exactly the same color and scale, and it's really beautifully done. Now when I look at the 99% original bike above the striping on the tank is much larger then what's on the rest of the bike. Also the tank emblem looks brand new. I contrast all my striping matches, and my emblem looks original. That said even "The Saints" bike has fat striping on the tank, Looks like those fat stripes worked for him. So who really knows. I mean it's not that big of a deal to me if the shocks were changed, or he put a darker windshield on it. It's almost 40 years old and things do get replaced. I love the bike anyway. It just would be interesting to know what was done to it, by whom, and when. Great stuff thanks for all the info, Jim
The stripe colour does look too dark, if it really matters to you. I suppose if trying to sell it on to a "knowledgeable" airhead it would cause discussion. The way the stripes taper is also unusual and not how I've ever seen them done. I'm guessing at an aftermarket job. Are they painted stripes? Jon Lars fine example.
Hand painted and really well done. The taper for each line is unique, and at a angle you can see density changes which all suggest it was done freehand. Amazing work. It puts the striping on my other BMWs to shame. Just looking at your pics it looks like there is a second stripe on the fairing that's not usually there. There is the top one under the windshield but also a second set below that travels down past the signal lights then crosses under the headlights. I used to paint cars for a living, and I've looked for evidence of repainting on the fairing etc.. and can't find any. If he had the bike repainted and striped he must of laid our a lot cash for the quality, it's just beautiful work.
The pinstripes are definitely different than any other 77RS I've seen - and I've got one. My opinion is the stripes have been re-done - non stock. I'm not saying it's good or bad, but the question is if it came that way and I believe not. I know what you mean about not riding it - I've got the same problem!
I see that the main advantage of twin plugging is the ability to run high compression ratios on unleaded. The other advantages are easier starting and a smoother engine. If Alfa Romeo did it it has to be right! My Euro 82 RT engine stopped pinging after twin pluggiing and Seibenrock suggest that you incorporate Ito engines using their 1070 kit. It is easier to do nowadays what with optimized dual plug ignition curves available from Sachse and Silent Hektik.
