Look at this: ACV-SB-061714
Sonex Aircraft requires the immediate replacement of all ACV-Z01-36 (3/4” long) Flat Head Socket Cap Screws that hold the Trigger Shaft Assembly (ACV-F01-24) to the Flywheel with ACV-Z01-81 (7/8” long) Flat Head Socket Cap Screws. The ACV-Z01-81 screws provide added thread engagement to help prevent these screws from potentially backing out. Applying Locktite Primer and 242 Threadlocker, and using the proper tightening procedure on these cap screws are also extremely important.
See the following AeroVee Installation Manual Page that references this hardware and details the proper assembly, Download: ACV-SB-061714_Flywheel_Cap_Screws.pdf
All AeroVee Engines sold since late 2012 include the longer ACV-Z01-81 Cap Screws.
Any AeroVee Engines sold before late 2012 that have the ACV-Z01-36 (3/4” long) Flat Head Socket Cap Screws on the packing list and/or installed can obtain new ACV-Z01-81 (7/8” long) Cap Screws at no charge. Please contact the Sonex Aircraft orders department to initiate this order, reference ACV-SB-061714 and include part numbers ACV-Z01-81, Qty 4:
orders@sonexaircraft.com