R50 engine question

[jevincj]

I picked up a couple basket cases and im trying to figure out what this engine is, the serial number is on the right side and is ground off. has 5 ring piston and the part number on the flywheel housing is 2521 01 801 20 thanks in advance.

 

[69zeff65]

Pictures would certainly help

Can you take a few of the motor and loose parts. It makes the identification a lot easier and more accurate.

 

[jevincj]

R50 engine

I was wrong serial number is on left side

 

[20774]

The number on the flywheel housing is a mold number and won't help with identification. If the VIN number that has been placed on the left side was to simulate the number that was ground off, then the VIN 630xxx equates to an early, like 1961-ish, R50/2. The stroke of an R50/2 is 68mm while the stroke of an R60/2 is 73mm.

 

[jevincj]

R50 engine

The right side of the engine has no signs of any markings. The weird thing is I have a r50/2 with numbers matching engine which is stamped on the right side of the block. Someone decided to grind the serial off this engine and stamp the same numbers on it as the 50/2 not sure why. So when we're the serial numbers put on the left?

 

[20774]

I don't where to find it and not sure if I remember correctly, but I'm certain that the later engines didn't have the big BMW letters cast into the block. Also, I think early on the numbers were on the left side...could also be that bikes prior to the /2 era had the numbers stamped on the left. It's clear, though, that if the right side is completely normal, then the number for this block was on the left. It would appear then that someone wanted to substitute this block as an R50/2 but in reality it was from some other year/model.

 

[jevincj]

Thanks for your help. The research I have done kind of points it to an r51/3. I could be way off on this but I also have a 1957 r50 sitting here numbers matching on right side of engine.

 

[20774]

I like your theory. And, welcome to the forum!!

Update...I just checked my '68 built R69S and there are the letters BMW on the left side of the block...but not as big as the ones your showing. I'm sure it's from another model.

Here are some pictures of probably an R51/3 where the engine case was repaired. The size of the BMW letters appears to be the same as yours.

http://bmwvmca.org/joomla/index.php?option=com_content&task=view&id=59&Itemid=37

 

[jevincj]

Thanks a lot. Hope to figure this out. Hopefully someone needs it.