The ads above are Google-sponsored. Clicking on them at every visit helps support this website! Clicking on something inside an advertisement helps much more! BMW Airhead (& some twins prior to Airheads) Motorcycles Model differences over the years. Technical details of importance. Including a chart on weights and capacities. Plus information to identify the model/year, if you do not have a serial number, etc.
© Copyright 2018, R. Fleischer 67B Identifying the year of production by serial and/or VIN number: Beginning in 1980, and the process not completed until sometime in 1981, U.S.A.-shipped bikes from BMW changed from a pure serial number to a Vehicle Identification Number (VIN). This new type of 'number' is a combination of numerals and alphabet letters, and the total length is always 17 characters. The tenth position character (beginning from the left) is the official production year.
As an example, for 1980, that was an 'A'. Each year following was one letter further in the alphabet. I, O, Q, U, Z, were all skipped. Beginning in 2001, a digit was used, with 2001 being 1, 2002 being 2, etc. Models might not use the 17 character VIN number system.
Nov 12, 2018 - The vehicle identification number (VIN) is a unique combination of 17 letters. Origin, engine size, model year, vehicle type, trim level and plant name. For example, A is for Audi, B is for BMW, G is for General Motors, L is for. Here you will find our favorite websites where you can decode BMW VIN numbers. If you are trying to find out what engine size, transmission type, features, factory installed options, paint code, serial numbers and even BMW campaigns this article is for you.
In every instance, BMW records can use the last seven characters, which are almost always just numbers to identify the year and model; and, indirectly, the color and how equipped when it left the factory. All brands of motor vehicles sold in the USA since the 1980-1981 transition era use the same 17 character VIN system. For BMW vehicles, there can be confusion between the year of manufacture and the model year. This has sometimes caused problems with titles and registrations with various States. The actual 'model year' motorcycle could have been produced near the end of the prior calendar year, due to the BMW company-wide vacation month in August and restart of production immediately after that vacation, in September.
There are exceptions & anomalies.most of these are such as when a BMW bike was manufactured even earlier and mysteriously is identified by BMW as the following year's model. This has happened with some Airheads and some Classic K bikes now and then. There is sometimes additional confusion, because, for 1984, BMW stopped stamping the last 7 characters of the 17 character VIN, always a 7 digit number, next to the oil dipstick of all engines. For very considerably more information about VIN and Serial numbers, how to read all 17 characters of VIN's, the sequencing, the anomalies, etc. See the following article: 'Airheads', for the purpose of this website, and this article, mean BMW motorcycles with the 2 cylinder boxer-layout engine style with two valves in each head, as produced beginning 12/1969 as 1970 /5 models. Airheads are generally considered as being in production into 1995 and possibly a few into 1996. Airheads are not the other boxer type motors that BMW produced, slangly called the Oilhead, Hexhead, etc.
Those are considered air and oil cooled, and have a very different type of engine design, which are also all fuel injected. Slash 2 is used generically, to mean the models more or less immediately before the Airheads; that is, before 1970. I don't get deeply into them.
They were generally produced in the fifties and sixties. The details in this article are not to be considered to list every year's change. I will add details to this article now and then. Models prior to 1970: This article you are reading has, in this section, information on models prior to the /5. BMW made some radically different bikes from 1923 to the end of WWII.
Overhead cams, single cams, dual cams, supercharged, besides the more pedestrian models, including single cylinder models that paid the bills. For a discussion of of these early bikes, refer to: 1. SLASH 2 information, many photos, some decent technical specifications, etc.
A major source and very worthwhile read: This is Jeff Dean's article, which describes the /2 series rather well:; I disagree only, well, primarily, with the engine oil recommendation.and, gearbox and rear drive too. A major source for technical information, parts, etc.
For early BMW's. Owned by Craig Vechorik, also known as 'Vetch'. There are few knowledgeable folks having a business that specializes in working on or supplying parts and information for pre-1970 BMW motorcycles, Vetch is one of them. Benchmarkworks is at 3400 Earles Fork Road, Sturgis, MS, 39769 USA, telephone: (662) 465-6444 5. The book: Illustrated BMW Motorcycle Buyer's Guide, by Stefan Knittel and Roland Slabon If you have a /2, you can install a 12 volt alternator and lamps conversion for much better lighting. Coil ignition can be installed (not needed IMHO). Using the best modern partial or even full synthetic oils, you can extend the time between /2 crankshaft slinger cleanings, although just how much is questionable, and depends on engine condition, particularly engine blow-by.
A worn engine allows more blowby, more contaminants into the oil, including more carbon, which fills the slingers faster. You surely do not want the slingers to fill totally.which causes oil starvation to some parts of the engine.
Use of a quality oil with ZDDP or ZDTP is helpful. The internals of the wheels of the /2 era bikes are very similar in basic design to the /5 and even into /6 airheads, but the /2 era bikes had larger diameter axles and frames that flexed less. This was because the motorcycles were designed to allow for sidecar use. The /2 era ended BMW's practice of 'sidecar fittings as standard'. This was made doubly so with the abandonment of the adjustable trail Earles leading link fork.which had been an option, or standard, depending on the model and ordering by the dealer. The /2 era bikes steering heads had ball bearings, which were not as good as the /5 and later tapered bearings, but they are installable.
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The /2 series ended the use of the very nice-looking bars-end turn signal housings. If you have, or are contemplating, the ownership of a pre-Airhead BMW motorcycle, be sure to extensively read up on them. The Airheads, general information: 'Airheads' are twin opposed cylinder air-cooled motorcycles manufactured between the end of 1969 (the beginning was the 1970 year model) and the end of production in 1995. For the 1970 models, the motorcycles are called Airheads by officionados. BMW made huge changes to these new production bikes, especially of note was the changes to the motor and frame. They also completely dropped, even as an option, their version of a leading link type front fork which is called the Earles Fork.
The last such huge changes were arguably in the R5 of 1936. The motor for 1970 had plain bearings lubricated by a high pressure system & there was a pleated paper oil filter. The camshaft position was changed to below the crankshaft. Previous motors had roller bearings for crankshaft & camshafts, low pressure oiling systems, and some form of 'filtering' that is generally referred to as a slinger or slingers. The electrical system had major changes. There is a long list of various changes.and I will get into most of the changes, later herein. The use of the separate rear frame on the /5 and later (most models) causes fitment problems, not nasty ones though, when fitting a sidecar to a /5 and later Airhead, which was specifically not officially allowed.
The separate rear frame structure, on those models having it, do cause some flexing, which was improved over the years of production. The /5 Airheads had a thinner front axle diameter than later Airheads (14 mm versus 17 mm); and some bending had been seen under severe conditions, hence the later factory change from 14 to 17 mm. This was easily accomplished by BMW by simply changing the internal spacers of the wheels, and the hole size in the fork lower legs.
There are websites and groups devoted to the early bikes. /5, /2, G/S, ST owners.and some others.also have their own websites. See this page: The primary immediate response source of technical information for all BMW AIRHEAD boxer models, made from 12/1969 to 1995, is not the single model websites in the above short paragraph, but the Airheads LIST: for information on how to become a Member of the Airheads LIST, which is free.
BMW has tended to find ways to use up old parts bins stocks, and has sometimes shipped various combinations of components; this was particularly so in the 1973-1976 era. It is fairly easy to swap many parts on many or all Airheads. While there is a lot of interchangeability possible on parts & components, this is not to be taken that all can be interchanged, or that just because some will physically fit, it is wise move. There are very specific problems, or concerns, in interchanging many items. It is possible to put some items from other BMW bike lines into Airheads. The Classic K-bike front ends & brakes, for example.
Actually, very substantially-built forks from other makes can be installed, as can alternators from Moto-Guzzi, Ducati, etc. Those thinking of swapping Airhead cylinders, cylinder heads, transmissions, rear drives, etc., can consult the Airheads internet LIST for expert advice, although there is information in my #60-x articles, & information on other things, like drive-shafts, rear drives, fuel tanks & seats, etc., found scattered in the appropriate areas on my website. I also have an article on modifications for performance: Not all models were shipped to the U.S.A. In any given year. Only a few are important, one of which is that BMW stopped shipping R100-engined bikes to the USA for a couple of years in the 1980's; and the R45 bikes (both versions) were never imported into the USA by BMW.
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Some of these various not-imported bikes are seen now & then in the USA, including the later R80GS and R80GS-PD with Paralever; the R65GS, R80R, 1995-1996 R100RT Classic (questionable about the importation of those, and note I listed 1996!!) and R100GS PD-Classic. Here is a good website page, showing a chronological index for BMW motorcycles with some specifications for each model. If you click on a model, you get a lot more information. Unfortunately, the site does not separate out Euro vs USA versions, and the site also includes the pre-Airheads, and the later models too. The Airheads, part 1: There have been a large number of changes to the Airheads over the years, yet there remained mostly similarities. This article does not show all changes, as there are too many. Cosmetics and finer details like tank shapes & fits; seats fits, etc.
Are generally not included in this article. However, there is an article on this website dealing with the changes to the instruments, from the start of production of the /5 to the end of production of the Airheads, in 1995: In late 1969 BMW stopped manufacturing all prior models and began manufacturing only boxer twins, beginning with the /5 series. The /5 was a radical departure from their previous motorcycles. Although BMW had conventional telescopic & leading link (Earles) forks on previous models, now only telescopic was offered.
The frame was considerably modified, and no longer wrapped to the rear. A separate bolted-on rear sub-frame was now used. I do not consider the new rear sub-frame an improvement.
As the years rolled on, BMW beefed up the frame to improve handling, but the separate rear subframe continued for some time. It contributed to the famous 'rubber cow' effect. Early models exhibited that effect much more than later models, and the Monolever and Paralever models had less of it. The rear suspension plunger design was abandoned in favor of a swing-arm design.
The plunger design is better for sidecar use. The /5 and every Airhead model.and all other BMW motorcycle models made since the end of 1969.were not designed for sidecar use; but most have had sidecars put on them successfully. The new engine design had a considerable number of changes. Mechanically, the biggest change was to move the camshaft location to below the cylinders, this improved lubrication. The pushrod tubes delivered the oil from the top ends to the camshaft lobes by draining downward inside the pushrod tubes. The engine internal oiling system was modified.
An oil filter was incorporated, where only crankshaft 'slingers' were used before. This new design eliminated the need to remove the crankshaft every 30,000 miles (approximately), for slingers cleaning or replacement. The 6 volt system was changed to 12 volts and the magneto was abandoned in favor of points & coil ignition.
A starter motor was added. In general, the longevity of the motor, and mileage between serious service intervals, was substantially increased. BMW motorcycles became more popular in the USA and began to get a more and more well-deserved reputation for being quiet, competent, and needing less service, and having fewer problems than most other makes.
The /5 came with a 180 watt 3-phase alternator. After the /5, higher capacity alternators became standard with the introduction of the /6 series. Certain early /6 series 280 watt alternators will fit the /5. The first /5 models had a shorter wheelbase (easily seen by a quick glance at the rear area of the black colored driveshaft housing, it has no welded section a few inches from the flange end).
This early /5 SWB (Short Wheel Base) and to a more modest amount the early R65 (also short wheel base, but production began on the R65 much later, in late 1978) could (not will), have some potential for instability under some specific types of riding.and in particular if a fork-mounted windscreen was installed (or a big bat-wing type) and worse if the rider had considerable weight aft of the rear axle and speed was high; big saddlebags and a rear trunk made things worse. BMW elected to go to the LWB (Long Wheel Base) in mid-1973, and for the R65 it was in the eighties, but no R65 model of any year had the same level of possible instabilities as the SWB /5. There is an article on this subject:. You can see the welded-in section, used for many years after it became standard.
The LWB (Long Wheel Base) also allowed for a bigger battery. My personal preference is the SWB. It feels quicker-handling. BMW incorporated the LWB in mid-1973. There was also the later addition of an internally cushioned driveshaft. The cushioning was provided by smooth-finished two-part mating-cams, whose actions were backed up by a very strong spring. It is better for the transmission to have the 'cush driveshaft', but not at all critical, and not required at all if shifting is done very smoothly.
There are some further advantages to the LWB models, including more stability with aft loading, better able to handle windscreens, and capability for a larger battery.the original being small in size. The SWB has a somewhat higher torque feeling if the throttle is suddenly snapped off, and this is more noticeable in turns. While not getting into it any deeper than a mention here, there was no hue and cry about instabilities at speed on the SWB R65.which out-handled any stock /5. & some of which was due to the top triple clamp being very beefy; even though the 18' front tire was possibly a negative. This is all arguable, of course. The /5 bikes had 10 mm flywheel bolts, and the 1974 /6 also did.these could be twisted off from serious rider abuse during riding. Some slightly later /6 may have them.perhaps into early 1975.
After this, the bolts were 11 mm. The bolt torques vary, and using the torque information on this website is a good idea.
In identifying a /5 engine block, there is an eyebrow cutout on the front face of the engine block. It is solid from 1974. Obviously, these are not viewable on a motorcycle with the timing chest & outer cover still on the engine. The /5 SWB bikes and /5 LWB motorcycles use different saddlebag mounts. The early R65 can be fitted with its own bag mounts, or /5 mounts adapted, and vice versa. The /5 with its 180 watt alternator came with a 40/45 watt non-halogen headlight. BMW offered a kit to convert to the much better H4 lamp, but the kit is NLA.
Converting the headlight, in some good manner, is an excellent thing to do for your /5 motorcycle. You have to change the lens too, or the light pattern is spread about rather poorly (but, see the next paragraph). You can easily adapt the R65 headlight parts to a /5. Conversion gives vastly better lighting at night, using a 55/60 watt H4 halogen lamp. Later bikes got rid of the clip method of holding the bottom of the headlight chrome ring.which sometimes allowed a headlight assembly to fall and be damaged.
Modification of early chrome rings to avoid loosing the ring, headlight, etc., is a good idea. The article has information on a H4 type lamp that will work with the original /5 reflector and base. The /5 models came with a crankshaft rear main-seal that tended to leak after enough mileage & maybe dirty oil helped that along.
BMW has made a number of mainseal changes over the years, & considering mileage & servicing, the chances are low to modest that you will find an original type of white seal. With the /6, BMW added an O-ring inside the flywheel bore & with the /7 came a metal cap and the same O-ring continued. The final version of the main seal has a Teflon section, & works very well, & fits all Airhead models.
The automatic timing unit (ATU) for the ignition was changed a few times too during the /5 era. The final version was in 1981. Model or Item Year Weight, lbs Notes R50/5; R65; R45; 452 R80G/S 423 With electric starter, std. Battery R80ST 436 No kickstarter, 1984 R65LS 456 R60/5; R60/6; R75/5; R75/6/; R80; R90/6.
463 R60/7; R75/7; R80/7; R90S; R100/7; R100T R80GS (1991+) 474 R90S, measured 452 dry. R80, measured 463 dry. Others without fuel, without tools, but with lubricants: 430 lbs. R100 481 R100S, R100CS 485 Without tools and fuel 441. R100RS 505 to 507 Measured 463 no fuel, for 1978-1979 USA models, but with lubricants.
R100RT 516 to 525 Depending on year. 6.3 gallon (24L) tank is assumed. Includes all lubricants and full fuel tank. Without fuel, 472 lbs. R80R 478 R100R 481 R80RT 500 R80GS PD; R100GS PD 1988- 1990 535 32L tank R80GS PD; R100GS PD 1991+ 520 Tested at 588 with full tank R100GS 1991+ 485 R80GS 1991+ 474 R80GS; R100GS 1988- 1990td 463 /6 transmission 24 Drained; without shift lever R65 LS rear drive 1982 16 Drained; with brake shoes Engine, R80/7 1978 140 With starter, with carburetors, without ignition coils, without intake system. Engine, R100/7, S/RS, RT 1979 138 As above Gasoline weighs 6.0 lbs per USA gallon. Lubricating oil weighs 7.5 lbs per USA Gallon.
Most early engines had 2.38 quarts of oil (0.6 gallon) (including the oil in the oil filter). Later engines had 2.64 quart, and later with the cooler had 2.91 quarts. Transmissions had 0.85 quart. Rear drives had 0.26 quart on early models, later ones 0.37 quart on all models except the R80R and R100R had 0.28 quart. Early driveshafts had 0.11 quart of oil, after which they had 0.16 quart (except for the dry shaft Paralever models). The front forks varied considerably.
For early models you can assume 9-1/2 ounces per each of the two legs; the GS models had up to 17 ounces per each of the two legs, and the R80R and R100R models had 14 ounces per each of the two legs. Because of extensive confusion on this subject, and recommendation changes by BMW, information is in its own article in a chart on this website: The /5 series fuel tanks held either 5.39 or 6.34 gallons.
Except for the models listed just below, most tanks held 6.34 USA Gallons. That capacity was not necessarily what you could, or not easily, fill the tank to, because later tanks had flapper valves (many owners removed them), and if filled to the flush-filler area, held 6.34 gallons. Note that BMW fuel tank specification includes the reserve, and the capacity is to full (whether or not you can fill it that much).
Some tanks vary a small amount in ways you might not think of, including the space for the ATE under tank master cylinder; and, BMW was not careful about specifying the difference in capacity between the early flip type caps and the later tanks with the screw-in removable caps.which either had a flapper valve (or not); but the neck, if not well-filled, detracted considerably from the fuel capacity. The actual reserve amount (included in the tank capacity) varied, and the left and right sides were not quite the same capacity, a cup to three cups difference.
The R80ST and R80GS had small tanks of 5 gallons plus a couple of cups. The RS & RT models generally held 5.55 gallons, although some held about 5.2 or 5.3 gallons. The PD models had large tanks with the R80GS PD holding nearly 8-1/2 gallons (a non-imported version had 26 Liters). A larger GS-PD tank was available, and sold with many of the bikes as standard, and it held 9-1/4th gallons. Revisions:: Minor typos. Numerous clarifications.: Add VIN information numbers at top of page; set space for additional serial & VIN number references. Minor clarifications, 247-248.: Brembo & Magura information; transmission hyperlink & transmission dating note & clarity of wording.: Re-arrange placement of some information, add hyperlinks; add things deemed important that had been left out previously.
Clarify a few details.: Update 1974 information.: Editing.: Minor editing.: Article number removed, editing entire article for clarity, page placed before all the rest on the T.I. Page.: Previously had no article ID number, now is 67B.: Remove hyperlinks to engineinternals.htm.: Typos and clarifications only.: Update article.: Minor clarifications.: Two minor clarifications on rotors and stators.: Quite a few updates, to help primarily with identification.: Notation regarding 105 mm alternator being seen on 1976 engine case.: Minor updating, and a bit more on.: Add link to Verrill's site page.: Minor cleanup.: Clarified a few details.: Clarified details on transmission gusseting for 1978 and 1979.: Had a request to expand the R section, so did so. 2013 April 2014: Remove problem causing javascript language button code; update article, update and add many links.: Move capacities and weights from other articles and put them all here, at the end.: Add some information to the chart on weights/capacities.: Add more information on models up to 1984-1985. Later, added info on more /5 to /6 changes.: Minor updating.: Expand upon the RS, RT, and faired bikes in general; and, fix typos with regards to them also.: Minor update, but add conclusions, about transmission circlips.: Update meta-codes, layout improvements, etc.: Fix scripts, numerous HTML errors, metacode, H.L., fonts. Narrow the table.: Expand slightly, information on 1985+ valve/seats updates, to show that some 85-86 were not shipped that way.: Revised article to greatly reduce font and color changes, clarify some minor details, etc.: Rework article, remove some redundancies, reduce some fonts and color changes, improve layout. Clarify some details such as on the wheels.: Add reference to the book by Knittel Slabon.: Update /2 era sources/information.: Add link to instruments article.: Add quote by T.C.: Minor updating, such as to mention the 1977 and 1978 R100S and its equipment, and notation about leaded fuel slightly expanded.
© Copyright 2018, R. Fleischer Last check/edit: Sunday, December 30, 2018.