I found a good replacement flywheel for my Johnson FD-12 project to replace the original one with a damaged taper and a couple of cracks in it. I now need to lap the replacement wheel with my replacement crankshaft and got to wondering how other folks do the lapping process. A few methods I’ve read about in the past include:
- Put the flywheel on the crank and turn it around and around in the same direction for a few revolutions.
- Put the flywheel on the crank and rotate it one full revolution in one direction, then rotate one full revolution in the opposite direction. Repeat a couple times.
- Put the flywheel on the crank and rotate it back and forth thru a 90 degree arc, lift it up and turn it 90 degrees from the original starting position and rotate it back and forth thru 90 degrees again. Repeat until a full circle is completed.
- Put the flywheel on the crank with the flywheel and crank keyway slots aligned, then rotate back and forth through a 15 degree arc either side of the crank keyway slot (30 degree total arc).
Even though the key doesn’t hold the flywheel in place, it seems like the last approach would help to ensure the best mating surfaces for the flywheel in it’s final installed position. Regardless of what approach is used, I know to protect the upper crankshaft seal area during the lapping operation.
Anyway, not wanting to start an opinion battle here, just curious what others have done!
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
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