TM 9-2815-250-24&P 3-6. CRANKCASE REPAIR (continued). 8. Remove upper crankcase (23) from eight studs (24) on lower crankcase (22).  Set upper crankcase (23) top down on work surface. 9. Inspect eight studs (24) and remove any bent or damaged    studs    from    lower    crankcase    (22). Discard removed studs. 10. Remove   two   gaskets   (25   and   26)   from   upper crankcase (23).  Discard gaskets. 11. Remove eight O-rings (27) from  eight grooves in upper crankcase (23).  Discard O-rings. b. ASSEMBLY 1. Apply  grease  to  eight  new  0-rings  (27).    Install eight   O-rings   (27)   on   eight   grooves   in   upper crankcase (23). 2.   Apply   sealing   compound   to   ends   of   two   new gaskets  (25  and  26).    Lightly  coat  the  rest  of each   gasket   (25   and   26)   with   lubricating   oil. Install    two    gaskets    (25    and    26)    on    upper crankcase (23). 3. Install eight new studs (24), if removed. CAUTION During installation of upper crankcase, rotate crank gear so timing mark on crank gear is between two timing marks on camshaft gear.  Failure to align timing marks correctly may cause damage to the engine. 4. With  the  aid  of  an  assistant,  install  upper  crankcase  (23)  on  eight  studs  (24)  and  lower  crankcase  (22).    Make sure  timing  marks  on  crankshaft  gear  (28)  and  camshaft  gear  (1)  are  aligned  and  that  two  gaskets  (25  and  26) and eight O-rings (27) stay in place. 3-22