Strip down the carburetor into parts.
5 gallon bucket with hot water, dish washing liquid and a small amount of ammonia.
Let it soak for hours. Use different size soft bristle brushes to go after the 50 years of road grime, oil, leaking gas stains and dead bugs.
Hot water to rinse.
Use compressed air to clean out all you can.
Repeat the above. I'm done when my cleaning solution is not as nasty black as before.
I usually have dirt in the compact areas and some slightly rusty parts so I use my soda blaster.
Soda works well but stay away from (or tape up) the tiny idle, vent, jet passages.
Cleaning out the passages is much more difficult if there is packed-in soda.
Use compressed air to clean out all you can.
Hot water to rinse.
More compressed air to clean out.
Let dry.
Plastic pics and toothpicks to get to tiny spots.
Pieces of Scotch-Brite pad to lightly buff pump wells/piston walls.
Hot water to rinse.
More compressed air to clean out.
Ultrasonic cleaner, warm water, dish washing liquid and a small amount of ammonia.
Let run for 20 minutes
Take parts out, rotate and put back in the cleaner.
Repeat.
Hot water to rinse and rinse well.
More compressed air to clean out and dry parts.
My ultrasonic cleaner does a good job cleaning very fine brass inlet filters and pump well strainers but it takes longer over many cycles.
