Crankshaft rear bearing internal circlip 80 x 2.0

This circlip (aka snap ring) fits into the rear main bearing carrier, on the outside (rear) of the rear man bearing's outer race. Basically it holds the bearing into the bearing carrier.

NOTE: The bearing should be a press-fit into that carrier. If you can spin the bearing's outer race within the carrier, inspect the carrier for cracks. If there are none, use some bearing retainer (e.g. Loctite 640) to keep it from spinning.

If you haven't damaged or distorted the old snap ring, you can reuse it. If it doesn't seem to fit properly (especially if it fits loosely), you'll want to replace it.

Stop reading now if you don't like too many details.

Regarding the sizing, 80 x 2.0 means it's 2.0 mm thick and is designed to fit inside a groove that is 80 mm in diameter.

As for the factory catalog's description, "B80 GOST 13943-86", that's a reference to the Russian industrial standard for circlips (in Cyrillic it's "ГОСТ 13943-86"). We've received them labeled as DIN 472 80 x 2.5 as well. (That's the much more internationally common German industrial standard.) That said, these circlips measure 2.0 mm thick. Looks like the ГОСТ 13943-86 specification has an A80 and a B80, and the B80 is this thinner one, while A80 is 2.5 mm thick like the DIN 472 spec. You could probably still use a 2.5mm thick one, but it might be difficult to get it to drop into the groove.