Probably a dumb question but......Is there anyway to tell if my pistons have ever been oversized? Performing a top end gasket replacement and I was just wondering. The bike has about 120k miles on it. Can post pictures if that helps.
I'm just guessing here, but I'm going to assume that "oversized" pistons are going to require a larger bore than stock. Stock bore is 82mm. If you have calipers, check your bore. Additionally, you can measure the piston with it at TDC to double check against stock size.
From Gemini via BMW MOA data:
The standard nominal bore size for a stock BMW R75/7 motorcycle is 82 mm, and the actual stock piston diameters are stamped on the piston crown (typically sizing designations like 81.965 mm, 81.975 mm, or 81.985 mm depending on the specific factory cylinder grading) to provide the necessary running clearance inside the 82 mm cylinder. [1, 2, 3]
Thanks. I will check the diameter. Can't read any stamps on piston head.
looks like they're both about 81.9 mm.
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