Chainsaw Repair

Most likely a 45mm then, going by your readings.  If it will clean up, I would put it back in service.  That's a good looking 55 you got there.  I've only rebuilt a couple of them, but were the open port which still made good power.  Certainly enough for cutting wood.  Be sure your plastic bulkhead (divider),  is in good shape.  Had to replace both on the ones I redone.