Motorcycle (mostly BMW-centric) glossary

I only just started in this whole motorcycle thing in summer of 1999. When I started out, I kept seeing these terms used by the motorcycle press, which everyone was supposed to understand. Naturally, it took me months of further reading before I figured out what was going on, and in some cases, I didn't understand until I actually owned and rode a bike for the first time, in November of '99.

I figured, if I had those problems, other people probably do as well, and I might as well help them out if I can. So I wrote up this glossary of motorcycle jargon for your enjoyment. I'm positive that I'm missing about 90% of the terms that confuse newcomers to the motorcycle world, so I'd love to hear your suggestions: send me email.

Since most of my motorcycle experience to this point is centered around BMW's, that will be a bias in this glossary. I'm not trying to exclude other brands, but there may be terms that don't often get applied to BMW's but are common in other circles. I'm also making the assumption that you, the reader, have experience with other vehicles (such as cars) and know most terms from that area. If you don't there are plenty of good car glossaries which can help you out.

The Glossary


The term "Boxer" refers to an engine style where a pair of cylinders are horizontally opposed to each other -- if you look at the two cylinders from the top, they're almost on the same line, on either side of the engine. When they fire, they do so on opposite strokes, but both cylinders move in towards the crankshaft and out away from the crankshaft at the same time. The result, at least in theory, is a vibrationless engine.

Notchy shifting

When someone says a shifter feels notchy, they mean that there's not a silky smooth feeling when moving the shift lever from one gear to another. It feels almost like there are "notches" you have to move the lever past in order to make a complete transition from one gear to another. Usually, if you stop when you hit one of those notches, you'll find a false neutral.

False neutral

A motorcycle transmission usually has 4 or five gears, plus a designated "neutral" -- a position in which the transmission doesn't power the rear wheel. This neutral is usually found between first and second gear. When you find a false neutral, you've shifted the transmission so that the gears aren't properly engaged, and it feels like you're in neutral again: the wheel's not receiving any power from the engine. However, this happens between gears other than first and second, which is bad. It usually means that gears and engaging levers are spinning with sub-millimeter clearance between them, probably doing Bad Things to the transmission. This is usually the result of hitting a particularly notchy transition between gears.

Bar-end mirrors

Bar-end mirrors are a style of mirror (arguably the most famous is the Napoleon brand) which attaches to the end of a bike's handlebars, just like the name suggests. The mirror is thus placed further out board than anything else on the bike (unless you've got huge saddlebags attached), and usually means you can see what's actually behind you, like with a car's mirrors.

BMW K-bike

In the early '80's, BMW decided to revitalize their motorcycle line up by replacing all the old Airhead R-bikes with a new style of bike that had an inline-3 and inline-4 engine, and many advanced features. The result was the K series of bikes (the K100, K75, etc.) These motorcycles have inline engines (the cylinders are lined up in a row, like many automobile engines), fuel injection, advanced suspension design, etc. All the latest greatest technology. The K-bike line was the first in the world to incorporate Anti-lock Brakes, in the eighties.

K-bikes are sometimes called "flying bricks" or "whining bricks" due to their brick-shaped engine, and the Jetson's-hovercar whining sound they make. The engines, while very advanced, powerful, and fuel efficient, are nearly impossible for an amateur mechanic to do much with. They are therefore a trade-off for those of us with a more limited budget.


R-bikes come in two flavors: Airheads and Oilheads. These two flavors share a basic engine layout in common, the Boxer, and not a whole lot else. They both look like motorcycles, and aside from basic things like wheels and handlebars, aren't too much alike. The Oilheads are clearly descended from the Airheads, but in the same way that a housecat is clearly descended from a tiger. (I won't hazard a guess which way 'round that goes.)

The term "R-bike" comes from the fact that motorcycles of this type are all named as R and then a number, like R65, R100 or R1200. Most of the motorcycles have a suffix, like LS, GS, R, RT, RS, etc. Each of these suffixes has a meaning, usually indicating a "body type" or "trim type" based on the same model. For example, an R100 RT is an R100 motorcycle with touring trim on it (big fairing, hard bags, etc.). An R80 GS is an R80 with modifications to make it more offroad worthy (GS stands for "Gelšnde/Strasse", which means "Field/Street" or "Country/Street").

Airhead R-bikes

Way back after World War I, BMW was prohibited from making any "machines of war," which primarily included airplanes. The brass at BMW decided that they'd like to stay in business, so they borrowed an engine design that reminded them of an airplane engine -- the Boxer -- to put into a motorcycle. That engine design stayed with them for a long, long time, and its penultimate (so far) form was the Airhead.

This is an engine that has two cylinders in the Boxer layout, and is air cooled. I won't even attempt to divine at what point in history BMW started producing Airheads, as opposed to whatever came before them. The engine is also normally aspirated, via a carbeuretor on each side.

The term Airhead can actually refer to either the engine, or the bike wrapped around the engine. Basically, Airheads were produced up until 1995 (I think) in the US, with the R100 Mystic.

Oilhead R-bikes

Oilheads are BMW's answer to consumer complains when they announced they'd be killing off the R-bike line in the late eighties or early nineties. They realized they'd alienate a big chunk of their customers, but they didn't want to keep flogging the poor Airheads, which were no longer even vaguely modern bikes. The result was the Oilhead, which is an Airhead engine warped 20 years into the future.

The term Oilhead comes from the fact that this engine type is oil cooled, and has oil flowing up into the heads. These engines really are drastically redesigned Airheads, with the basic layout being the real resemblance to the Airhead. Fuel injection is used instead of carbeuration. Engine control computers are normal on these bikes. New materials were used in the construction of the engine. The bike which goes around the engine is also different, with a greatly upgraded suspension, gearbox, clutch, appearance, etc. (Well, I say upgraded appearance, what I really mean is "different" appearance -- I don't like the new looks much.)

I think Oilheads first appeared in the early nineties, '92 or so. I may be wrong about that, though. Consult the BMW timeline, listed on my main page for a precise account.

High-side crash

This is the name for the type of crash where the motorcycle over-balances, flinging the rider off by pivoting around the tires. It usually happens in turns, or as the final phase of a tank-slapper. Crashes of this type commonly leave the rider injured or dead, due to the impact of hitting the ground after being flung off.

Low-side crash

This relatively benign crash occurs when the tires lose traction in a turn, and the motorcycle slides away from the rider. Assuming the rider is wearing protective gear and doesn't hit anything solid, there's an excellent chance of getting up completely unharmed from a low-side. The motorcycle will usually suffer abrasion damage, such as scratches on the fairing, or a broken turn signal or hand lever. This damage is commonly minor enough that the bike can be ridden safely afterward.


When just the right conditions are present, the handlebars on a motorcycle can start oscillating uncontrollably from side to side. Most commonly, this happens at high speed, or when there's not much weight on the front tire (such as while accelerating). Steering dampers are installed on some motorcycles to prevent this from happening.

The advice I've read for dealing with a tank slapper is to release pressure on the bars (gripping harder usually makes it worse), and gently roll off the throttle. This is no guarantee of making it stop, but there's a chance of reducing it, so it's worth trying.

Tank slapper situations commonly end in a high-side crash.

Back to the R65 page

Created by Ian Johnston. Questions? Please mail me.