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size plain bearing bsa a10
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Remember, if you’re unsure about the size or condition, it’s best to consult an engineer familiar with old bikes. Happy wrenching!
For sizing the big end shells and main bearings on your BSA A10 motorcycle, here’s what you need to consider:
Big End Shells:
The big end shells ride on the crankshaft journal. Over time, the journal wears out, gradually becoming smaller. If the shells become too loose, it can lead to issues like reduced oil pressure and knocking noises.
To determine the correct size, follow these steps:
Inspect the Journals: Examine the condition of the journals. If they are worn or damaged, you’ll need to get the crankshaft reground to an appropriate undersize.
Check Shell Markings: When you remove the shells from the rod, they are usually marked with a part number or undersize.
Standard Size: The standard big end journal measurement for the small journal crankshaft is 1.4595-1.4600 inches.
Worn or Damaged: If the journal is more than 0.002 inch worn or is oval or damaged, it requires regrinding.
Regrind Sizes: Refer to the attached photo from the BSA service sheets for regrind sizes. The main bearing journal -0.020 measurement should be 1.3540-1.3534 inches1.
Main Bearings:
The main bearings consist of a roller drive-side and a white metal plain bush on the timing side.
The standard main bearing journal measurement is 1.375 - 1.3745 inches.
Remember, if you’re unsure about the size or condition, it’s best to consult an engineer familiar with old bikes. Happy wrenching!
