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Airheads

What's an "airhead"? In addition to the well-known blonde female stereotype, an Airhead is a BMW motorcycle of the type that was built from when they first were produced in 1923, until they were finally discontinued in 1995. Technically they are referred to as the "Type 247" family in BMW-speak. They are two cylinder aircooled motorcycles with the two cylinders opposed to each other, therefore the cylinders stick out from the sides of the motorcycle and are cooled by the passing air, which is where the airhead moniker came from.

BMW makes two other major series of motorcycles. The Oilhead, or Type 259, was introduced in 1994 to replace the Airhead. Oilheads are also two cylinder horizontally opposed engines, but get their name from the fact that a larger percent of the engine cooling function come from the engine oil circulating internally. The other major family is the K-bike. Introduced in the mid-80's the K-bike was controversial because it was the first water-cooled BMW ever. This adds complexity and weight, but also allows higher engine performance. The K-bike and Oilhead bike families are currently being produced, but Airheads, having been discontinued since 1995, are now owned and ridden by those who appreciate their simplicity, quality, and unique characteristics. A very active and loyal community of enthusiasts exists, and those who ride Airheads are often called Airheads themselves.

"Simplicity is the highest statement of the design engineer's art".
(from BMW Motorrad's 1979 product brochure)

What's the attraction to these old German bikes with a design that dates back to 1923? I mean really, there's plenty of great newer technology available, including in BMW's line. Well, there's just something about the way these stately machines glide down the road that I've grown to appreciate over the years. They transport you at their own pace and in their own manner. They are dignified and idiosyncratic at the same time. Those who actually work on their machines appreciate the quality of the materials and construction, very German. I've owned at least one model from each BMW family (Airhead, K-bike, Oilhead) and appreciate the distinct character and qualities of each. Still, Airheads are what I keep coming back to for their simplicity, their quality, and their distinctive mannerisms.

The R100RS has always been the top of BMW's line. It was the first motorcycle in the world with a fairing designed in a wind tunnel, quite revolutionary when it was introduced in 1976. It was designed to not only control the airflow around the rider, but to generate downforce instead of lift to make it more stable at speed. In addition to being functional, the RS was simply beautiful to behold. It quickly became one of the most desireable bikes around. The various road tests of the day provide insight into the character of the bike well, especially Cycle magazine from December 1975 when the RS was first announced. To me this ad from 1979 says it all...

In 1979 I bought my first BMW, and it was a new one... a 1978 R80/7 that was a last year's model on closeout for $3,799. This was a LOT OF MONEY but I somehow managed to swing it. What I really wanted of course was an R100RS but simply couldn't afford it. When I bought my R80, the RS was around $7,000, just to much for me. The '82 model has several important updates over the orignal RS, but the fundamentals still apply.

 

1982 BMW R100RS

Before...


Looks ok from a distance, but look closer.
Hmm, I think this'll be a bit of work.
(clic on a pic for larger image)

Having always lusted for an RS I finally decided it was time to do something about it. After searching for a couple of months I found this 1982 RS in "Polaris Graphit", one of the few factory airhead paint colors ever done without the trademark pinstripes. It was originally sold in August of '82 from a dealer in New Hampshire to someone who rode it a bit then stored it for many years. The msrp in 1982 was $7,350. After years of it sitting in his garage the original owner sold it to a friend in early 2003 who intended to convert it to an RT but discovered that wasn't really feasible. I bought it in November of 2003 when it had 3,877 original miles on it, really.

Many airhead officianados consider the '81-'84 range the "pick" vintage because in 1981 BMW introduced several key improvements including Nikasil cylinders, a new lighter flywheel/clutch assembly, and electronic ignition. The '81 thru '84's were also the last series of twin-shock models with all subsequent airheads featuring a monoshock swingarm and K-bike wheels and brakes.

Even with the very low mileage, this was still a 23 year old motorcycle that had never had most seviceable items serviced. On anything this old most rubber parts will have degenerated, there may be small areas of corrosion in places unseen, and I just didn't want to be riding around on a bike this old unless I knew that everything was properly serviced. Therefore I set about to essentially disassemble the entire bike to make sure everything was correct. Disassembly revealed a few more problems than I had anticipated. For example the muffles were rusted from the inside out. Although the bike had been stored indoors, the wheels had corrosion on them requiring refinishing.

Once apart, everything was inspected, replaced if necessary, refinished if at all blemished, and essentially brought back to new condition. I then began piecing everything back together with every serviceable item check and/or serviced.

 

The restoration process

Summary of service & restorative work:

  • Disassembled -- all major body/chassis components removed.
  • Swingarm & rear drive removed. Swingarm repainted, rear drive housing acid etched, primed with zinc primer, repainted. Swingarm bearings refilled with Valvoline Synthetic grease. All reinstalled, swingarm bearings adjusted.
  • Transmission removed, clutch assembly inspected for wear or damage, none noted. Transmission input spline cleaned and lubricated with moly grease, transmission reinstalled.
  • Kickstand modified by Bo Stewart with improved tang and scuff pads, powdercoated & reinstalled.
  • Front wheel replaced in accordance with BMW recall. Rear wheel sandblasted, painted with Griot’s Garage zinc primer, German Silver Wheel Paint, and Clear Laquer.
  • Wheel bearings repacked with Valvoline Synthetic grease, bearing preload set to spec, new seals installed.
  • Michelin Macadam 50/50E tires and Michelin AirStop tubes installed and balanced by Portland Motorcycle.
  • Rear wheel drive spline cleaned and lubricated with moly grease.
  • Steering head disassembled, bearings found to be damaged. Old bearings & races removed, new bearings installed, packed with Valvoline Synthetic Grease, preload adjusted to spec.
  • Forks disassembled & inspected. Reassembled with new OEM fork springs, 7.5 wt BMW fluid installed.
  • San Jose fork brace installed, forks aligned/adjusted to minimize stiction.
  • Cylinder heads serviced by Oak Okleshen including: cleaning/decarbonizing, new exhaust valve seats, new exhaust valve guides, new exhaust valves, intake & exhaust valves ground (valve job) to BMW spec. All parts BMW OEM updated design & materials.
  • Cylinder heads reinstalled with new gaskets, torqued to spec and valve clearance set to .006” & .010”. Rocker arm endplay noted and minimized during assembly.
  • Rear drive, drive shaft, and transmission oils replaced with BMW 80W/90 GL5 lube.
  • Engine oil filter changed including drain/refill oil cooler. Engine refilled with BMW 20W/50 oil.
  • Carburetors disassembled, cleaned/inspected, jets replaced with 165 mains, 48 pilot, 2.68 needle. Needle located in 3 rd notch, float levels set to spec. Carbs reassembled & reinstalled. Note: carbs were recently rebuilt by Max BMW prior to purchase including new diaphragms & seals.
  • All rubber brake lines replaced with braided stainless steel lines from Bob’s BMW. Front & rear brake systems flushed & bled. Pads inspected, 70% pad remaining.
  • Exhaust headers, crossovers, and mufflers replaced with new OEM parts.
  • Diode board replaced with Omega unit, solid mounts installed on top two mounts, Omega replacement ground wires installed on bottom two mounts. Alternator & brushes inspected, no problems noted. OEM Wherle voltage regulator replaced. All parts from Motorrad Elektrik.
  • Headlight assembly disassembled, cleaned, reassembled with PIAA SuperWhite H4 bulb.
  • New Ikon rear shocks installed.
  • New Hepco-Becker saddlebags from Bob's BMW with black BMW brackets.
  • Miscellaneous other parts refurbished or replaced.
  • Ignition timing checked & reset to spec.

Airhead valves & seats

One of the things those interested in airheads will first need to know about is the situation with the valves and seats. Here is a concise recap...

Pre-1981 models were designed to run leaded fuel. With the phaseout of lead in gas, the problem of VSR (Valve Seat Recession) became acute. In 1981 BMW addressed the lead issue by changing the valve seat metallurgy. Many respected and knowledgesble people believe that the material BMW selected was incorrect, leading to another, similar problem, called VFPD (Valve Face Plastic Deformation). BMW re-addressed the issue in 1985, changing the valve seat material once again, and releasing new valve seats for fitment into earlier models. This "final solution" was the one that seems to work. Many older 1970's era airheads can go very high mileages with little or no VSR, due to the lead impregnation of the seats from way back then. The residual lead seems to provide protection for the life of the seat, until it is recut, at which time VSR may occur on a rapid scale. 81-84 models need to be addressed/updated at some point but the time and mileage can vary widely. Watching for changes in the valve adjustment over time is the accepted method of determining the need to update the valves and seats.

Work log

Clic on pics for larger version. They are large pics so you can see detail so be prepared to wait...

BEFORE: piston top and head

 

AFTER: all cleaned up and with new exhaust valves, exhaust valve seats, and exhaust valve guides, all of the newer materials that work with unleaded fuel and will not be subject to valve seat recession or VFPD. Piston top was decarboned also with Scothrite pads.
RIGHT: with the swingarm, rear drive, and heads back on the reassembly process continues.

AFTER: rear wheel and drive housing after sandblasting, priming, painting with Griot's Garage #20225 Zinc Primer, #20229 Silver Alloy Wheel Paint, and #20230 Clear Laquer.

LEFT: The new front wheel from BMW with their beaufitul new paint. Good news, it matches what I did with the back wheel very closely. You would have to scrutinize it closely to tell the difference!

 

After

 

All told I think it turned out well. After going through the bike as I have there is no question the mileage is accurate. Notice also that there is none of the sun damage (faded parts) typical of a bike this age.

 

Resources I've found useful

Airheads.org
Boxerworks.com message board

 

 

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