1974 BMW R-Series, in Black

1974 BMW R90S.
I have decided to sell my very special 1974 R90S.
This bike has been the subject of a no-expense spared restoration. My intention was to create a “stock appearing” bike, but significantly upgraded with an emphasis on performance and reliability. In the process the bike was entirely disassembled. Every casting was then vapor-blasted before being reassembled with new bearings, seals, and fasteners, the great majority being stainless steel.
I have used only top quality or NOS parts throughout.
The bike starts, idles, shifts, runs beautifully, and its performance is very significantly improved. This is an extraordinarily clean and well sorted machine. I ride this bike regularly, and have put on about 800 miles since the restoration. It is a delightfully smooth and swift beast! I ride it aggressively, and am not afraid to give her the beans!

A quick note about me: This is the 18th motorcycle I have owned. By day, I am product development executive, and I regularly work with a large network of highly qualified craftspeople with specialized tools and machines. I place no time or financial limits on my builds, but rather prioritize technical excellence and quality of execution. I work on them for the sheer pleasure of it. I strive for museum quality. I've included a few pictures of the build, and you can decide for yourself. Why am I selling? For me, the fun is in the building, and I have other old BMW's which are demanding my attention.
Originally, this bike was purchased from Bob's BMW as one of their project bikes. It was not running, and looked as if it had been stored for at least 30 years. The fairing was missing, but it was an original bike that had not been abused.
The odometer shows about 22,000 miles, and I have no reason to believe that is inaccurate.
The serial number is 4071086 (matching engine, frame, and build plate) giving it a build date in November of 1973. This is a very early bike, and the SN is officially that of a European bike. As far as I can tell, this is number 1086 of 5072 units produced in 1974, the first 968 being Europe only. That would put it the first 100 units brought to the US. It's a little hard to tell exactly, but it has all the unique hallmarks of the first gen bikes, which were finished to a higher standard and slightly different specification than the later, somewhat cost-reduced bikes. Here is a quick list of 1974 peculiarities:

● Smoke-silver paint only. The Daytona orange color was introduced the following year.
● Polished aluminum turn signal housings. Later years were black plastic.
● Polished aluminum gas cap.
● Black-anodized levers with finger grooves.
● White circles around the speedometer and tachometer gauges
● Switchgear similar to the outgoing /5 motorcycles
● Unique pattern to the seat vinyl.
● Chrome acorn-nut on the rear drive.
● Undrilled front brake disks, 38mm calipers (this bike upgraded to 40mm)
● Chrome plated horn
● Curved mirror stalks (Impossible to find. This bike has later mirrors)
● Gold stripes applied via tape rather than paint

Restoration details by category:
Powertrain:
Carbs are the original Dell Orto PHM38 units, and have been disassembled, vapor blasted, fitted with all new brass, floats, springs, gaskets, jets, needles, gaskets and cables. The early R90S had a metal “bent tube” fitted to the carb tops. This was later eliminated due to regulatory reasons. The original parts are NLA, but I have gone to the trouble of fitting later tubes, which required the original carb tops to be welded and re-tapped for the new threads. I have gone through 4-5 jetting changes and have settled on its current close-to-stock setup.
The engine is fitted with a race-lightened flywheel from Motoren Israel in Germany. In addition, it has a Schrick 332 “sport” cam. As far as I can tell, this cam profile is identical to the famed BMW 336 cam fitted to the racers of the day. Cylinders and pistons are 1000cc Siebenrock 9.5:1 units. The Siebenrock pistons are of a more modern design, and are much lighter than the stock ones. I went to the trouble of ceramic coating the cylinders black to both mimic the original R90S look and provide higher heat shedding capabilities. Heads have new valves, 3 angle seats, and double springs in addition to lightened spring retainers. Head work performed by the very reputable Bombar's Beemers. The bike has a new EME starter, voltage regulator, and the EME crank-mounted electronic ignition, paired to new Bosch “super coils.” This engine likes to rev! Though it has adequate torque to chuff around at 25mph in top gear, things get interesting after about 4500rpm. It happily and oh-so smoothly builds power all the way to it's 7000rpm redline. Some folks would caution about combining a big cam and light flywheel for a street bike, citing concerns about difficulty in getting such an engine to idle. All I can say is this bike idles beautifully at a slightly higher than stock 1400RPM, and the faster you go, the more this engine seems to like it!
The clutch is entirely new. Splines on the transmission are in excellent shape and have fresh lube. I installed an EZ clutch device which both reduces lever effort and doubles the perceived clutch engagement range at the lever. The feel is light, fast, and precise.
So much has been written about airhead transmissions, it will boggle the mind. The 1974 5-speeds have a few known weakness, all of which have been addressed. In fact, for this bike, all possible upgrades have been installed. First the weaknesses—the kickstarter gear was too soft in 1974 and tended to deform un use. This has been replaced with a properly hardened one. The big weakness of BMW transmissions of this era are poorly machined shifting dogs which tend to break. Upon disassembly, sure enough, a broken shift dog was found, and I actually procured a needle-in-a-haystack replacement for the entire gearshaft assembly. While apart I installed the so-called “shift kit” which improves shifting positivity between gears and makes finding neutral easier. It also has the “ball bearing detent wheel” upgrade which improves shifter feel. For those extra-paranoid BMW guys, yes, this transmission has the circlip. All bearings and seals are new, and the unit is shimmed to the tight side of factory specification. It shifts smoothly and quietly, with far less effort and a lot less “clunk” than the four-speed in my /5.
Brakes:
I have put a lot of effort into getting the front brakes to perform well, and believe these are now fully optimized. BMWs of this era utilize an unusual cable-operated under-tank MC, and unique ATE “swinging” single piston calipers. Though considered adequate in the day, the stock brakes perform way below modern expectations. As a remedy, this bike has both higher specification components and improved geometry. The pads are upgraded to a modern Ferodo compound from Vintage Brake. Lines are stainless steel. Most importantly, the master cylinder has been re-sleeved (twice!) to a smaller diameter by Apple Hydraulics, and I have switched the calipers from the stock 38mm units to slightly larger 40mm units from a later model. Since very few people have bothered to go this route, getting the brakes right required two tries and more money than I like to think about. The new calipers were ceramic coated, and have new stainless pistons and all new seals and new hard lines installed. It was important to me to keep the original disks, as in 1974 only, they were undrilled. How does it work? Braking performance is now excellent, for a 50-year-old bike; they feel almost modern. While they could never compare to a new sportbike system, three fingers can easily lock the front wheel at speed. They are light-years better than stock.
Frame and Suspension:
The frame has been stripped bare and inspected. One minor crack on the right exhaust hangar was found and repaired, before being repainted by Precision Motorcycle Painting. New steering head and swingarm bearings installed.
The fork has been disassembled, vapor blasted, and fitted with all new seals and gaskets. Springs are new from Racetech, and calibrated to a 190lb rider. The original damping system has been upgraded with Racetech cartridge emulators. Upper triple clamp is from Toaster Tan, has been custom milled to fit the R90s binnacle support, and was painted along with the fame. A vintage fork brace has been fitted. I believe this one is from San Jose BMW.
Wheels have been fully renovated. Hubs were vapor blasted. New bearings fitted and properly pre-tensioned. Rims are NOS units procured from Meyer Bikes in Germany. They were brought over, re-polished, and then the wheels were built up with new stainless spokes by Woody's Wheel Works. Tires are new Michelin Road Classics. I even went to the trouble of finding vintage style wheel weights.
Rear Shocks are new IKONs with adjustable preload and damping. My last bike used YSS rear units, and I find the IKONs to be a little nicer.
Handling impressions? Firm, planted, and beautifully damped front end! A stock bike has a very long travel softly sprung fork, creating a lot of dive under braking. This bike feels much more modern. While one can still feel the 36mm tubes flex under hard braking, front end dive has been vastly reduced, while providing good absorption of bumps, and vastly improved damping. Handling is benign and predictable. Actually, it's way better than that—BMW airheads are legendary for their ability to cover great distances in great comfort. I find the riding position of this bike to be near-perfect.
Other things:
The front fairing is a NOS unit purchased from Meyer Bikes in Germany! The rest of the paint is 50 years old and original. There is a small ding on the front fender, and a few airhead-typical scratches and small dings on the tank. Honestly, they drive me crazy. I have thought long and hard about repainting it, but every single BMW guy I have spoken to seems to value the original paint more. The next owner will have to make the choice. All the badges are new, and the roundels are nicer-than-stock enamel units from Toaster Tan.
I removed sidestand and installed a Brown unit, because I found the stock unit borderline dangerous.
Headers are new Keihin stainless steel units and are just gorgeous. Mufflers are the original and have some light rust speckling. I would expect them to be replaced at some point. I have a set of bags installed which I consider to be included for free. They are very early Krauser units and are somewhat rough. Since I didn't consider them worth restoring, I simply covered them with stickers. Having said that I did clean them up and I replaced the locks with more modern ones. I use them regularly. The new owner can throw them away if desired. The clocks on these old things are sort of special. Originals have white numbers, have a mechanical movement, and are almost universally inoperable. The only real fix is to keep the original housing and replace the movement with a more modern quartz one from a later bike. I did this and the clock keeps good time! However, in re-crimping the bezel, I cracked the glass. I expect to repair this before the bike is sold.

It's a legendary model, and this is a fantastic example of one of the first off the line. Every issue with the bike has been addressed, and the modifications only enhance the innate goodness of the platform. It is meticulously constructed, and beautifully tuned. Premier examples of these bikes have recently hit record prices of $60,000. In terms of restoration quality, this bike is not much more than a paint job and a set of mufflers away from that standard. When you put it all together, this bike is a bargain at $20,000.