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I’m doing a full restore on my Briggs and Stratton 20HP Opposed Twin. While taking the engine apart entirely for cleaning, I noticed the Crankshaft and Piston Journals have minor scoring. They are only visible scratches, and they do not catch on my fingernails. This is my first attempt at a full restore on any engine, and all I need to know is if these Piston Journals And Crankshaft can be cleaned with Emory Cloth, or if they need to be replaced. Any help will be deeply appreciated. Thanks.

The crank will polish up with some steel wool or Brasso or 1600 wet & dry used wet.
Emery is way too rough.
As for the rods, get new ones, they are cheap and never worth playing with.
By the time they get crack tested &/or x-rayed you have exceeded the replacement cost , let alone a shut & Cut to bring the rod back into proper specs.

Buff the crankshaft, replace the rods..

If they are starting to paste aluminum on the crank, that is.

How many more hours do you intend to put on this engine? If the answer is "not many" I'd just put it back together as-is. Anything you do with emery cloth will only make the crank and rods out-of-round with more clearance.

If it's going to be put back into regular service, I'd replace them.

That is normal on an old engine, as long as the journals are within spec don't worry about the crank. Do replace the rods, cheap insurance.

Seems like the usual failure on the higher horse old school Briggs twins are conn. rod breakage. For sure, replace those. I'd check the crank for out of roundness, if good, clean it up and run it.

cpurvis said:

How many more hours do you intend to put on this engine? If the answer is "not many" I'd just put it back together as-is. Anything you do with emery cloth will only make the crank and rods out-of-round with more clearance.

If it's going to be put back into regular service, I'd replace them.

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I plan to do somewhat both not many hours and full service, mainly because I intend to not only mow the lawn but also pull a disc around in the garden with the same Murray lawn tractor this engine came off of. The disc is the bigger reason I'm fixing this thing up because the Troy-Bilt pony lawn tractor's transmission is not optimized for pulling garden equipment. As for the lawn, I plan to swap out the original blades on the deck for mulching blades for when we decide to let the grass grow to full maturity so I can cut the grass easier when it reaches that stage.