I agree with Ron - that's not an accurate method. Correct is to turn the carb upside down and VERY carefully set the float "level".
In other words, the float tang that lifts the needle (in normal orientation) should just touch the needle when the float is carefully lowered to the level position. Bend tang as needed.
It's not ultra-critical so no need to be anal, just get it as close as you can by eye.
As for lapping the seat, the seat isn't supposed to be lapped in - in fact it's supposed to be a square edge (the seat) contacting a tapered needle - the contact is therefore only a narrow line, not a flat surface. All that matters is that they are both ROUND, and the seat edge is SQUARE. (if that makes sense

) The needle should be replaced when there is ANY sign of a groove worn around it.
You MIGHT be able to salvage the seat by lapping the
surface with a square ended, hardened steel, round shaft of appropriate diameter to get the top surface flat and square - could be worth a try. Use a drill to power the shaft!
Otherwise, look for a good used carb - they're not too hard to find at a wreckers.
hope that helps, and best of luck,
------------------
Grant Johnson
Seek, and ye shall find.
------------------------
One world, Two wheels.
www.HorizonsUnlimited.com