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Old vs.  New style /2 BMW motorcycle cylinders

by Duane Ausherman

This page is about the /2 BMW motorcycle models. 

The cylinders used from 1951 up to about 1960 are the "old" style.  From about 1960 to the end in 1969 are what I call the "new" style cylinders.  This applies to all twins from 1955 through 69.  I can't remember if it also applies to the singles.  Maybe someone can tell me and I will include the info here. 

The difference is in the lubrication of the pistons.  BMW provided forced lubrication only to the left cylinder of the "old" style.  It was expected for the crankshaft to "splash" enough oil onto the right cylinder to provide piston skirt oil.  The crank does not provide enough splash for the right side and seizures, or collapsed pistons are common.  In about 1960, someone help me here, BMW added oil pressure lubrication to both cylinders.  The problems caused by lack of lubrication were solved. 

The "new" style cylinders can be used on the older engines.  They fit and seal perfectly.  Still no oil will be supplied to the right piston skirt.  However, one can even drill a hole into the oil galley and get the lubrication to the right cylinder.  This requires some knowledge, but isn't hard to do and is a great upgrade. 

The problem comes in when one tries to use an "old" style cylinder on an "new" engine case with the hole for oil pressure.  The shape of the old cylinder base is such that the oil pressure hole won't be covered and it may leak badly. 

The gaskets for the two styles are also different.  The original gaskets were all paper.  Later on BMW went to the metal ones.  I seem to remember that they also supplied metal ones for the "old" style cylinders.  I think that the paper ones sealed better, but were much harder to clean off after 15 years of use.  I prefer the metal ones.  I always use a very thin film of sealer on the gasket. 

Here are a two photos to show the differences. 


                                                                                      New                              old

New style cylinder photo supplied by Lonnie Walker, thanks. 

The cylinder on the left is the new type and the one on the right is the old style.  The holes shown in the center of both are to return the oil from the valve cover area to the crankcase.  Both types of cylinders have this hole.  The crankcase is different and the old style won't cover the holes in the case properly. 

cyl_style3.jpg (16227 bytes)

The metal gasket on the left is the new style.  See the three holes? Only two are used, but with three, it doesn't matter which way the gasket is installed, it has no "front" or "back." The gasket on the right is the old style.  See the difference in shape of the coverage? One of the two outer holes in the new gasket will have oil pressure.  If the wrong gasket or cylinder is used, it will leak badly. 

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This page was last edited: 04/07/2006 - copyright Duane Ausherman
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