The view in the rear view mirror is always different than the view through the windshield.
Twenty years ago, in early 1993, BMW introduced the R1100RS, the first of what would become known as the Oilhead and later the Hexhead and the Camhead. After a hiatus of eight years, BMW was unveiling the new generation “boxer,” opposed two-cylinder motorcycle.
The one and only Paul Glaves
Voni and I drove to Kansas City for the dealer open house and model introduction. It was a somewhat wet and gloomy day. Voni had read all about the new model and was excited to see it. I went for the free donuts and hot dogs. We didn’t intend to take a test ride and certainly didn’t intend to buy any new motorcycles. The rain dried up and soon I saw Voni strolling to the front door of Engle Motors with a borrowed brown leather jacket, yellow open face helmet, and nondescript gloves. One test ride later and an intervening weekend in the interval, on Tuesday, May 11, 1993, she became the owner of a red 1994 R1100RS. It was among the first handful delivered to the United States. She still owns and rides Big Red.
When it was introduced, many Boxer enthusiasts didn’t know what to think. Here was a 1,100 cc essentially air-cooled, opposed-twin motorcycle with fuel injection instead of carburetors, a 700-watt alternator instead of 280, a Telelever front suspension and low profile radial tires. It was dubbed the Oilhead because it was equipped with an oil cooler and large cooling oil passages in each head. The oil pump had both a high pressure–low volume circuit for lubrication and a low pressure–high volume circuit for cooling.
Now, with Voni’s 368,000 miles on that bike and 135,000 miles on another nearly identical 1994 R1100RSL, and my 170 or so odd thousand miles on an R1150R, I can look back rather fondly on the Oilhead at twenty.
Like almost any totally new model anything, the Oilhead had a few birthing pains. In fact, the earliest 1994 R1100RS bikes were soon dubbed “beta bikes,” borrowing a term from the ranks of information technology and software. If memory serves me correctly, BMW went through two or three revisions to the clutch disk material because clutches were wearing too quickly. They replaced many (maybe most, if not all) of the original transmissions under warranty.
The earliest model R1100RS bikes had three-spoke wheels that were quite soft. These wheels were and remain no match for the potholes found on many streets and highways. They bent easily. BMW assured us they were designed to be soft so they would bend rather than break. But somehow, when BMW introduced the next generation wheel design, the wheels neither bent nor broke with any regularity. The compromise workaround riders found to attempt to protect the three-spoke wheels was, and remains, to increase the air pressure in the front tire from the recommended 32 p.s.i. to 36–38 p.s.i. for solo riding.
The most serious early problem experienced by some, but not all, owners was the tendency of the motorcycle to surge under steady-state, light throttle conditions. Curiously, the beta bikes almost never surged but the later models did. The problem was a lean surge due to the extremely lean mixture designed into the engine control unit. We learned from experience that very careful tuning of the engine would usually eliminate the surge, but not in all cases. Several different components, each with its own tolerances in specifications, contribute to the overall mixture. Typically some components are within specification but to the rich side, while other components are within tolerance but to the lean side. Then on average things are OK. But on any bike where the tolerances were stacked to the lean side for several components, surging could not be eliminated by tuning. Thus began a lot of experimenting and eventually some aftermarket devices to fool things to make the engine run richer.
By the time the R1150 models were introduced, surging remained an issue for some but not all Oilheads. The second generation of R1150 bikes were dubbed “twin spark” bikes because each cylinder was then equipped with two spark plugs. BMW chose to use coils for the second spark plugs mounted directly atop the spark plugs. I wish they had simply gone to twin tower conventional coils because over the years many of the so-called “stick coils” failed, often due to the fact that they are mechanically fragile and easy to damage when renewing spark plugs. I have heard of dozens of stick coil failures and almost no conventional coil failures.
The design of the new boxer engine used in the Oilhead placed the camshafts in the heads, not as an overhead cam design, but way out at the heads nonetheless. The valves are actuated by very short push rods and rocker arms. Each side of the engine was equipped with a very long cam-driving chain. Because of the design, and the changes in dimensions as the cylinders heated and cooled, a ratcheting, locking cam chain tensioner like that used on the classic K bikes couldn’t be used. BMW used purely hydraulic cam chain tensioners, one for each cylinder. The tensioner on the right cylinder screwed up from the bottom of the cylinder. The tensioner on the left cylinder screwed down from the top of the cylinder.
The left cylinder cam chain tensioner was in essence upside down and oil could drain down past the tensioner piston and out of the tensioner. This caused an annoying clatter when the engine was started, especially when the engine was fully warmed up. The clatter was always annoying and could be damaging. The cam chain was slapping until the hydraulic tensioner was recharged with pressurized oil. Rarely, but occasionally, the slapping chain would break a cam chain guide.
Unfortunately, if a guide broke, it could (by the book) only be replaced by removing the engine from the motorcycle and splitting the cases. BMW introduced a revised left side cam chain tensioner which wouldn’t leak down. The revised part was put into production mid-stream with the R1150 bikes and may be retro-fitted to the earlier bikes.
No discussion of the Oilhead at twenty would be complete without mentioning final drive failures. In truth, the number of failures has not been as slight as claimed by many dealerships, but has also not been as great as one would infer from reading the Internet. In total, only a small percentage of final drives have failed; but this is slight comfort to anybody who has suffered a failure. When one’s only vacation trip is ruined by a failure in a far away land, a person is likely to take it personally.
Final drive failures were almost unheard of for the first five or six years after the Oilhead was introduced, but then began to happen at what seemed to be a frightening pace. BMW was not forthcoming as to what the cause might be. Many different theories were postulated on the Internet and at fireside chats as to what the problem was. Some of these theories were blatantly wrong and some were at least partly right.
In the simplest terms, almost all of the failures were caused by what a bearing design engineer described to me as "bearing fatigue.” Simple but less than explanatory! When pressed for further information, he explained that in layman’s terms, the problem is that the big ball bearing races are going “metal-to-metal” against the rolling balls too often, too long or too hard. The bearing should have a sufficient film of gear oil in the space (clearances) between the balls and races at all times. Thus, bearing failures and almost all Oilhead final drive failures can be explained by any or all of the several factors that would cause the balls and races to go metal-to-metal too often, too long or too hard. Among the most prominent factors:
- Improper lubricant, either too thick or too thin.
- Final drive assembly shimmed too loose, allowing pounding.
- Final drive assembly shimmed too tight, reducing bearing clearances.
- Excessive load on the bearing from too much weight.
- Excessive pounding due to rough road and terrain conditions.
While some reasonable people believe that all or most failures are caused by a single, simple reason from the list above, I have personally concluded that a combination of one or more of these factors working together has caused the vast majority of failures.
With the introduction of the R1200 series to the boxer twin lineup, BMW changed the design of the final drive. A few failures still have occurred, but they tend to be most often initiated by leaking seals rather than bearing self destruction.
Like their predecessor models and most anything mechanical, the Oilheads have parts that wear and need periodic lubrication, examination or replacement. Clutch and driveshaft splines need cleaning and lubrication. Driveshaft universal joints eventually wear and driveshafts need to be replaced. Clutch parts wear. Brake pads and disks wear. Brake fluid needs to be changed.
The upside to the Oilheads in this regard is that they are sophisticated, powerful, fun to ride modern motorcycles. The downside is that maintenance procedures are some regards more time consuming, if not more difficult.
All of the above not withstanding, the Oilhead and successor Hexhead and Camhead models have been a mainstay of BMW production and highly popular models among BMW MOA members. With the introduction of the latest partially water-cooled boxer now dubbed the “Wethead,” I think the tradition will continue well into the future.