BMW R100 Engine Teardown - What Decades of Neglect Really Look Like

The engine of this BMW R100 motorcycle had been sitting idle for decades Today we'll completely disassemble it to see what time has done Later it will serve as the foundation for a unique custom bike project If you're curious about the direction of this project please join us I'll break it down Laid out on the table are most of the engine components so let's quickly go over their pros and cons Starting from the top the cylinder head appears to be in decent condition but to properly rebuild it I believe new components such as valves springs guides and seats will need to be installed The rocker arm has not yet been disassembled as it may still be changed The cam follower is in poor condition Out of the four only one is acceptable the other three are damaged One has a pit near the center while the other two have small notches in the circle We need to figure out how to handle these This is where things really get interesting with the engine The left connecting rod appears to be fine but the right one is completely bent The cause is not yet clear Looking at the pistons the one on the right appeared to be in a rich condition Based on my assessment the carburetor on the right may have been delivering too much fuel or fuel might have overflowed into the cylinder before starting which could have ultimately led to the rod's bending We welcome your feedback—please share it in the comments below The cylinder has not yet been measured but visible wear is evident at the bottom of the bore Even if the dimensions are within tolerance new pistons will likely require bore and honing work but this isn't a major issue The left cylinder has damaged fins and must be repaired before machining can proceed Rotating components such as crankshafts and camshafts are carefully measured to ensure accurate work on a healthy substrate After thoroughly cleaning the block we also inspect the oil pump The crankshaft journal itself appears flawless but the front main bearing shows signs of possible wear The main bearing has two prominent dents and several scratches The journal appears undamaged so there's no visible sign of foreign material trapped inside but the bearing definitely needs to be replaced Most covers are cleaned and reused for this project The engine block is thoroughly cleaned before precision measurements are taken ensuring it is fully prepared for complete reassembly The component on the right side of the table can be reused with minor repairs The component on the left will be repaired replaced or modified to make this engine truly unique Thank you for your attention Until next time—stay tuned