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Old 11-05-2013, 08:49 PM   #1
flemsmith OP
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What fits what in airheads...

Recently bought an 85 R80RT. I notice a fair number of parts I look at on ebay seem to end at 84. I'll be trying to figure out what the differences are where I can, just wondered if there was some source that ID's the major things that are unique. I'm aware it's a monolever, and I believe the same year R80 and the R100 have pretty much the same parts except for the engine, mebbe even just the cyl/pistons? But how about earlier years?
fer instance, the throttle perch I have has no screw on the bottom that would let me use that flip lever throttle lock.
And will headlamp mounting ears from any R80 or R100 work if/when I want to take off the fairing?
Gauges work, but they look crappy, can anyone point me to a source for replacement bezels and glass? Stuff like that. Appreciate any input, I'm an airhead newb, but you guys (and this bike) seem like too much fun!
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Old 11-05-2013, 10:51 PM   #2
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1) Get a manual - a Haynes (sp?) might let you know when the major mechanicals changed.

2) Look a the part numbers - some will tell you when they started to when they finished ... or what has superseded them.

Places that have a history with these have on line parts ..and some of those will tell you when they start to when they finish .. motobins in the UK for one, they also have a handy FAQ/hints section containing years of knowledge.

Things like the instruments bm declares as nonrepairable ... but others have found ways ... there is a speedo shop in the states that will service them..

Go slowly and listen/read .. but filter the info for noise.

Be carefull with the throttle perch - think the latter ones are missing the hole due to cost cutting. And the earlier ones may have a different gear tooth...
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Old 11-06-2013, 01:01 AM   #3
disston
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On line parts sources will be a valuable source for this info;

http://realoem.com/bmw/

http://maxbmw.com/

These are the two sites I use most. Since you are new to this there is a warning about this particular effort. The diagrams usually show parts in an exploded and logical format but you must be careful when assembling that the diagram is not used as the actual directions. They will trick you up and there are many places that the assembly order is not right on the parts diagrams.

If in doubt ask.
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Old 11-06-2013, 04:36 AM   #4
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There's an inmate here, wirespokes, that fixes gauges

As regards engine parts, they are fairly interchangeable, my 79 is running block,
barrels and pistons from an 86 with the 79 heads for example, there is quite a
few differences though, gearbox input shafts and flywheels and such, some early
cylinders won't fit your bike without machining

When I built my first airhead snowbums article on model differences was very
helpful, the whole site can be hard going but it's worth it for the basics on whats
what

Headlight ears from earlier bikes will fit yours, my 87 has /5 ears, the later ears
are a bit nicer looking though IMO. I had to thin down the rubbers and I used an
earlier headlight, you could modify your existing headlight to hold the ignition on
the left hand ear

As disston has said if in doubt ask, you shouldn't be long waiting for an answer
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Old 11-06-2013, 07:27 AM   #5
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There are some things that come up so often it is hard to not know. But remember, not all changes are divided by model year, some changes take place in the middle of a model year's production.

There is the earlier or later cylinder spigots. The block was originally drilled to take a cylinder that had a skirt that fit into the block with a diameter of 97mm. These are the spigots, the skirt. Early blocks with 97mm spigots are 1969, /5, through 1975, part of /6, production. Beginning with the production of 1976 blocks all blocks are drilled for 99mm spigots. This change happens on the line between 1975 and 1976 so if you should say for instance that you need cylinders for a /6 bike you will have to stipulate the year.

Along with the change of the spigots the pushrod tubes got bigger on the later bikes. There is a different push rod tube rubber for 1976 than 1975. If you are ordering parts for a 1975 bike you may have to give them the Vin# to get the right part. I had to do this. They gave me the wrong pushrod tube rubbers twice because they thought I was giving them build date instead of model year.
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Old 11-06-2013, 01:03 PM   #6
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now that is good to know-- since i happen to have a 1975 model.
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Old 11-06-2013, 01:34 PM   #7
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We do constantly tell people to learn to use Mr Snowbum's Tech Pages. There is a wealth of info there. I stumbled across this page tonight and thought it fit this thread very well;

http://bmwmotorcycletech.info/models.htm
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Old 11-06-2013, 04:51 PM   #8
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Quote:
Originally Posted by disston View Post
We do constantly tell people to learn to use Mr Snowbum's Tech Pages. There is a wealth of info there. I stumbled across this page tonight and thought it fit this thread very well;

http://bmwmotorcycletech.info/models.htm
"We"? I can think of a number of very trusted inmates (not including myself since I am a noob and a charlatan) that warn against using snowbum. The guy is not right as often as he is right and that is a LOT of not right.
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Old 11-06-2013, 10:31 PM   #9
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You've also got to watch out for some of the riffraff that sneaks in here from the idiotnet.

Join up with the airheads on micapeak - a lot less noise there.

In response to your question - there were several significant model changes during the airhead line from 1970 to the last one in 1995. Big changes occurred in 74, 76, 81, and 86. Those are the more significant dates, but as disston said, BMW regularly introduced changes mid model year. The best advice is to not assume anything! No matter how logical it seems they wouldn't change it, or similar it appears.

In 1984 BMW decided to end the airhead line in favor of the brand new K model that was to be THE NEW BMW motorcycle. But the customers made such a fuss, that BMW came out a few years later with the monoshock airheads. A lot of things are different about them - different front and rear ends, exhaust, bodywork and wheels to name a few.

Oh, and you may have noticed that supershaft doesn't like snowbum. He also doesn't like Haynes or Clymer manuals (they contain errors), or most of the guys who have websites telling how to fix your bike. Even the factory manual has errors. We've tried to get him to create a site with all the correct data - but don't think that's ever gonna happen.

More to the point - hopefully you've got mechanical experience working on your on vehicles. Pay attention to your instincts - if something doesn't make sense - check it out. Bring it up with us. Sometimes it's nothing, others it's a big camouflaged pit that will cost you in time, sweat and money.
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Old 11-08-2013, 07:46 AM   #10
DoktorT
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Quote:
Originally Posted by supershaft View Post
"We"? I can think of a number of very trusted inmates (not including myself since I am a noob and a charlatan) that warn against using snowbum. The guy is not right as often as he is right and that is a LOT of not right.
Yes, do please provide one, count 'em, one, specific example. Just one.
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Old 11-08-2013, 08:32 AM   #11
supershaft
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Originally Posted by Wirespokes View Post
You've also got to watch out for some of the riffraff that sneaks in here from the idiotnet.

Join up with the airheads on micapeak - a lot less noise there.

In response to your question - there were several significant model changes during the airhead line from 1970 to the last one in 1995. Big changes occurred in 74, 76, 81, and 86. Those are the more significant dates, but as disston said, BMW regularly introduced changes mid model year. The best advice is to not assume anything! No matter how logical it seems they wouldn't change it, or similar it appears.

In 1984 BMW decided to end the airhead line in favor of the brand new K model that was to be THE NEW BMW motorcycle. But the customers made such a fuss, that BMW came out a few years later with the monoshock airheads. A lot of things are different about them - different front and rear ends, exhaust, bodywork and wheels to name a few.

Oh, and you may have noticed that supershaft doesn't like snowbum. He also doesn't like Haynes or Clymer manuals (they contain errors), or most of the guys who have websites telling how to fix your bike. Even the factory manual has errors. We've tried to get him to create a site with all the correct data - but don't think that's ever gonna happen.

More to the point - hopefully you've got mechanical experience working on your on vehicles. Pay attention to your instincts - if something doesn't make sense - check it out. Bring it up with us. Sometimes it's nothing, others it's a big camouflaged pit that will cost you in time, sweat and money.
I have nothing against snobum personally. It's all the mis-information he puts out that I object to. It's the same deal with Plaka, for instance. Most all people complain about snobum's and Plaka's writing and mannerisms. I have nothing against ALL that. What concerns me is the misinformation they both spew. For a while, I seriously wondered if Plaka wasn't snobum!

I also NEVER said that I don't like the Haynes or Clymer manuals. I have repeatedly advised that I find them more reliable than the idiotnet time and time again. I have also repeatedly advised that no manual OR website is perfect but some of them are a lot better than others. Snobum has somehow become god like to many. Here on the idiotnet not too many people warn against his faults. Here on the idiotnet people think that independent thought should only be expressed on your own website. A website is what gives you credentials to have your own thoughts. Otherwise, shut up and nod yes like the rest of us! Off the idiotnet? Doubt and disillusionment is not only tolerated but encouraged from what I have heard with my own ears but I have been riding and working on airheads since the mid seventies so I tend to hang around the literal 'old school'.

supershaft screwed with this post 11-08-2013 at 08:55 AM
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Old 11-08-2013, 09:35 AM   #12
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Quote:
Originally Posted by supershaft View Post
I have nothing against snobum personally. It's all the mis-information he puts out that I object to. It's the same deal with Plaka, for instance. Most all people complain about snobum's and Plaka's writing and mannerisms. I have nothing against ALL that. What concerns me is the misinformation they both spew. For a while, I seriously wondered if Plaka wasn't snobum!




OP, your query got me to thinking- before I was really aware of forums I spent a lot of time with Google and various airhead searches; I actually think it is how I found snowbum's page.

It has since disappeared into the ether, but the long,long ago version of the boxerworks forum was a wealth of technical type info.

ibmwr.org was also a jumping off point.

It's funny, part of riding an airhead seems to include steeping oneself in the lore.
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Old 11-08-2013, 12:59 PM   #13
dilandau
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hey, I love it all. I thank the manuals and the various websites and opinions. I am indebted to Brook Reams for his site:

http://brook.reams.me/bmw-motorcyle-...build-project/

for a great visual guide to rebuilding many parts of his r75/5. His site in combo with various manuals got my bike from parts to current commuter- particularly in the clutch transmission and drive train areas.
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Old 11-08-2013, 01:06 PM   #14
disston
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Transmission changes. (if I make any mistakes on this let me know and I will correct it later)

The /5 bikes had the same transmission as the /2 bikes except for the input shaft splines and some internal changes. Also the air filter hook up was different. So a /5 won't fit a /2 or vice versa but some of the internal parts will swap. /2 guys want the shifter eccentric parts from your /5 four speed.

The all new 5 speed transmission starts in 1974 with the /6 bikes. A number of transmissions had broken gears the first year and the shifting forks and grooves they run in were redesigned. Because of this most of the parts in a 1974 transmission are unique to that year and can't be swapped into another year transmission. (you could use the shafts) The neutral switch is only used this year and some of 1975, so it is unique. The shift mechanism goes with this switch.

If a 1974 transmission is kept in good order it does seem to last longer but there are many that broke and if not lucky finding parts can be expensive to repair. The '74 thicker fork set up seems to be in more than '74 bikes.

A big change in the clutch for 1981 makes for a big change in the transmission. The bike feels more peppy and accelerates faster because the flywheel has been eliminated and it is replaced by the clutch carrier. Getting rid of the flywheel was getting rid of a lot of rotating mass that the engine doesn't have to rev up to reach higher rpm's. The new clutch carrier uses a shorter input shaft and so these transmissions are now known as the "short input shaft" transmissions. The earlier, 1974 through 1980, transmissions are known as "long input shaft" transmissions. This is the biggest thing to keep in mind when swapping around whole transmissions, short of long input?

There are other issues with whole transmissions but they are easier to handle. The Paralever drive shafts don't have oil in the swing arm so the rear transmission seal is different or at least installed differently. Some transmissions have a shift linkage instead of just a lever and all these parts can be swapped to any 5 speed trans. The trans cases lost their smooth appearance and got the waffle design in 1979 so a long input in '79 and '80 looks like the later transmissions.

When the clutch changed and the input shaft got shorter the rear cover of the transmission also got redesigned. All of the parts in the rear cover for the throw out operation are different. Early clutch carrier throw out bearing set ups can jam in the rear cover bore but the later one piece design will usually fit and eliminate the problem.

The gears in an Airhead 5 speed are square cut except for 3 which are Helical gears. The Helical gears are cut at an angle. This angle was 15* in bikes manufactured up thru March of 1982. After 3/82 the gear angle was 17.5* The two designs do not mate. If you need one of these gears in an early trans and used parts can not be found then you would have to change all three of the Helical gears. Because the gears on the lay shaft are not sold individually this starts to get expensive because you would have to buy an entire lay shaft. The later 17.5* gears are called "X" gears because they are usually marked with an X on one of their faces. However there are instances of X gears found with out their X. I think that the gear and at least one bearing has to be removed to check which gear is on the shaft. The X's aren't visible when the gears are in place. (I'm not sure of that, all my transmission parts are earlier pieces)

There was an improved shift mechanism used starting in mid 1981 but it was not used on all bikes until much later in all 1983 model bikes. BMW used to sell a kit to retro fit these parts to any 5 speed but the parts have only been available individually for many years now. The kit is still available from MotoBins in England. It is said the shift kit will help prevent the broken Pawl Spring problem which could strand you stuck in any gear, can't shift to any other gear but if in third gear you should be able to ride it home. And it also helps to eliminate the common problem of false neutrals.

The most famous transmission change made by BMW over the years was the elimination of a circlip on the output shaft sometime in late 1984. This circlip is holding the bigger bearing on the output shaft from shifting. Over the years there have been numerous failures of 5 speed transmissions of these bikes with the missing circlip. If the transmission has not failed and is being rebuilt before there is a problem then it is recommended to have the groove machined to add the circlip. BMW started putting the circlip on again after about 9 years of no circlip. The last year or some of the bikes built the last two years do have the circlip. The exact dates of which bikes got or did not get the circlip is not known. It seems to be a hit or miss thing I think. Snowbum has been collecting dates of transmissions opened to try and see if there is a pattern but I don't know if he has come to any conclusion yet.

For further reading please see;

http://bmwmotorcycletech.info/
Much info on all aspects of Airhead mechanicals. Transmission info may be found in several places.

http://www.largiader.com/
Also much info. A little better organized and so easier to read.

http://w6rec.com/
Mostly about 4 speeds. Much old school info and fixes that work.

There are many other sites around the Web detailing different riders rebuilding their transmissions. I don't have a list of all of those but have enjoyed them. Google is your friend.
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disston screwed with this post 11-08-2013 at 01:21 PM
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