later model/earlier model airheads

When reading some of the technical articles in BMWOn there is reference to "on earlier model airheads" or "on later model airheads", is there a specific year when these designations start or stop?
Thanks rg

There is definitely no official cutoff although I would say that most lump the '81 and later model bikes together as "late Models".

There are undoubtedly those who will say the "early" bikes predate the introduction of the /5 series. I think 1981 was the year BMW did away with the aluminum aircleaner box, so if those are "later" models then everything in-between would be "middle"?

Excellent campfire question...

As the saying goes, it depends. IMHO earlier/later varies depending on what technical aspect is being discussed. BMW used the /5, /6, and /7 designations to denote significant changes. Within each series, there were numerous model year and production year "running" changes e.g. long wheelbase /5's, needle bearing rocker arms, larger camshaft seal, double tube frame backbone, redesigned engine crankcase, external rib gearbox, Nikasil cylinders, Brembo brakes, electronic ignition, single sided swingarm, etc. etc. that can be considered earlier/later within the respective series. Spend an hour or so browsing the parts diagrams on one of the dealer websites and you'll be amazed how many parts are tagged "up to" model/year/chassis number and "commencing with" model/year/chassis number. In very general terms, I consider the /5 and /6 as early, and the /7 as later, with the post 1980 models latest.

BTW earlier and later also applies to the R65 models; I generally lump the R65 into two groups, the 1978-1980 models as early, and the 1981 - end of production as later.

sgborgstrom said:

There are undoubtedly those who will say the "early" bikes predate the introduction of the /5 series. I think 1981 was the year BMW did away with the aluminum aircleaner box, so if those are "later" models then everything in-between would be "middle"?

Excellent campfire question...

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The airbox went square in 1981 but it is still aluminum under the black paint.

I think 1969 and the intro of the /5 ushered in the modern era. Pressure oiling and flipping the camshaft and crankshaft were the last major changes in the architecture of the air cooled flat twin engine.

When I decided to get an Airhead, I decided to consider a late model to be anything 1985 and newer. The 85 and newer models have the valves fixed for unleaded gas, monolever rear suspension and the excellent dual disc brakes (or already had) like I had on my K bikes. The earlier models had a lot of changes over the years but the 85 and newer models stayed pretty much the same until they were discontinued.

osbornk said:

When I decided to get an Airhead, I decided to consider a late model to be anything 1985 and newer. The 85 and newer models have the valves fixed for unleaded gas, monolever rear suspension and the excellent dual disc brakes (or already had) like I had on my K bikes. The earlier models had a lot of changes over the years but the 85 and newer models stayed pretty much the same until they were discontinued.

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I always think of monoshock models as late models. 85 and later along with the gs and st.

tkpinsc said:

I always think of monoshock models as late models. 85 and later along with the gs and st.

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I tend to agree with this the most...I've had a '79 and an 82 and an 83 and the differences are minimal compared to the monoshock models.

No, the 1981 changes moved the Airhead from farm equipment to a modern motorcycle.

Although bikes with the 247 Airhead engine were NEVER approved by BMW for sidecar use, the 1970-1980 engine still retained the inordinately heavy flywheel related to sidecar use, which, combined with extremely heavy clutch action made them not so pleasant to operate.

Add to that the previous cable-controlled master cylinder for front brakes, and the the 1981 switch to handlebar-mounted master cylinder completed the massive improvement of the hand controls and added much improved braking besides.

Then, of course, the 1981 addition of electronic ignition--COMPLETELY maintenance free--brought the 247 engine into the the modern era, as did the nikasil cylinders as well.

BMWs have always been "parts bin" bikes and the the switch to K-bike suspension components for 1985 was a relatively minor change in comparison to the 1981 changes, and featured a couple retrograde steps, i.e. loss of tube-type tires and the reduction of front wheel size that is stylistically incompatible with RS and RT fairings.

For the '85 bikes, BMW did improve the exhaust valve seats and the wiring harnesses, but reduced reliability of the starter motor and the transmission at the same time, a not particularly positive outcome in total.

Oh yeah, BMW finally approved a "top box" for the '85-on models--woo hoo.

lkchris said:

No, the 1981 changes moved the Airhead from farm equipment to a modern motorcycle.

Although bikes with the 247 Airhead engine were NEVER approved by BMW for sidecar use, the 1970-1980 engine still retained the inordinately heavy flywheel related to sidecar use, which, combined with extremely heavy clutch action made them not so pleasant to operate.

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HEY!!! I like driving my tractor at ridiculously fast speeds and being able to break rear wheel traction downshifting into curves! I like being able to roll on at really low rpm's and have torque there! What do you mean not so pleasant? All that hand excercise is excellent for becoming a better guitarist and bassist. Works for me!

Square air filter assembly clarification
The black square aluminum airbox was phased in commencing with the 1980 models. The air filter cover was initially made of aluminum, not plastic. The early square air filters had soft rubber sides. When BMW switched to the hard plastic sided air filters, it was necessary to modify the cover with a dremel or file in order to make it fit onto the filter. It was a lot less hassle to purchase a new plastic cover.

Also, the design of the snorkels on the early covers caused a flat spot in the torque curve. BMW issued a service bulletin which instructed the dealer to drill 4 1/8 inch holes in the end of each snorkel to correct the problem.

There was also a problem with the SAS reed valves in the airbox. the early ones did not connect to the carburetor vacuum ports as on the later models, and IIRC, cold air was sucked into the exhaust port on deceleration, possibly causing warped/split exhaust valves. The new style SAS valves can be retrofitted. A small hole must be filed on either side of the airbox at the bottom front corners for routing of the vacuum hoses to the carbs.

FYI

lkchris said:

No, the 1981 changes moved the Airhead from farm equipment to a modern motorcycle.

...

made them not so pleasant to operate.

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Oh, gimme a break.

Don't see one of the newer ones in your list.

lkchris said:

Don't see one of the newer ones in your list.

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1974 - 1988 pretty well covers it.