New Lycoming crank recall MSB 566
 

This MSB has expanded the scope of an earlier AD to include some four and lower hp six cylinder cranks not previously thought to be of concern. 1227 cranks on some O-360, IO-360, O-540 and IO-540 models manufactured or overhauled after March 1, 1999 may be affected. Cracks and breakages caused by improper alloying may lead to failure. If you are flying a suspect engine, please check with Lycoming to see if you are affected.

The bulletin can be found here:
http://www.lycoming.textron.com/supp...tins/SB566.pdf
Good Luck,
Mahlon
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