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found something odd.

Roguetek

New member
so I bought a pile of parts from an older gentleman, who was cleaning out a storage.

it it, I found this...

According to the serial number, it's a 1974 R90S. But it's got this odd machined flat spot on the outside of the motor, down at the bottom.

Anyone know what that is?

20130601_092759.jpg
 

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Snowbum mentions a milled flat area in about the position you show...3 inches by about 1-1/2 inches. He seems to indicate that it was mostly 1983 or so and on, but not 1970s bikes. This area contained information about the production of the engine, but he said it could be blank, too.

If that's what this is, I wonder why it appears on a 1974 block?
 
If that's what this is, I wonder why it appears on a 1974 block?

The same reason my 12/'72 build 1973 R75/5 has the hydraulic steering damper mounting tab on the frame ... per Paul ... practice, just gettin' ready for the next model.

Is it just me, or do you all see TWO images posted above?
 
Just found this on RealOEM in ALL (European and USA) R90S Engine > Engine Running/Gear > Short Engine

4.png


Under the "Engine Block" heading, the boss does not appear.

3.png


This is the previous-life, technical illustrator in me surfacing. These are great old school illustrations ... from different viewing angles no less.
 
Fiche diagrams can be notoriously wrong...or general in nature. That said, if what Snowbum said is near correct, that this boss didn't appear until the early 1980s, did it really take BMW 8 years to "practice" that? I can see a few years prior, but that seems a bit much.

And I see two pictures...of the same thing.
 
ebay

'74 R90S

serial number 4930124 ... nice breather mod, eh?
$T2eC16JHJGYE9nooiL)qBQWimCtJ2g~~60_57.JPG


1978 R80


$T2eC16RHJG!E9nm3q(3)BRPmV87g6w~~60_57.JPG


'83 R100

034.JPG


edit - almost looks like it was intended to be part of the lubrication system... (?)

kinda curious how a double image post occurred. but just curious.
 
My '78 R100/7 block...there's too much inconsistency here...there must be some other variable not being considered. European vs Rest of the World?
 

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Some countries in Europe (Germany is one) require the engine serial number to be included in the title. When you take your vehicle to the mandatory technical inspection (T?V) every two years, they check the engine number. This is why it has to be in a halfway accessible spot. Therefore, some motorcycle manufacturers moved the engine serial number from an original (hidden) place to another spot where it could be seen. Maybe that is what you have here. A block that was intended for use in one of these countries.
 
checked mine, the 1406th off the line in Nov. 1973, no auxiliary numbering plate on lower left side of block. Numbers easily read standing up by oil filler and right upper frame gusset.

could be wrong, but that lower left block info spot showed up after '77?
 
Something odd

My 1977 R100S has the same machined pad on the left front of the block. I stamped my initials on it as a discrete means of identifying my bike/engine if it were ever stolen.

Glen M.
Member #12067
 
Glen -

Since you how Canada as your home, is your bike a Euro model? That might be the reason some have it and some done. My '78 R100/7 is a US model...no pad.

Interesting, though, that BMW would have two separate molds for the block, one with and one without the pad.
 
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