TM 10-4930-204-13(3) Inspect valve springs for cracks or pitting. Replacecracked or pitted springs.(4) Inspect valve seat insert for looseness and pitting.Replace defective valve seat insert in the following manner:(a) Use a puller to remove insert from exhaust valveopening.(b) Clean all carbon out of insert counterbore incylinder block and clean valve stem guide bore.(c) Finish counterbore in cylindler block to providecorrect bore-to-insert interference.Chill insert with dry ice and,using a pilot driver, tap insert into place with light blows. Peeninsert to anchor in place.(d) Reface insert, if necessary, to make its seatconcentric with valve stem bore.Check concentricity with a dialindicator.(e) Grind valve in seat to form a gastight seal.c.Regrinding Valves.(1) Regrind valve, valve seat, and valve seat insert onlywhen there is evidence of warping or deep pits.(2) Using a valve seat grinding tool, grind seats at a 45degree angle and then grind the valve faces at a 45 degree angle witha valve refacer grinder.(3) Valves must be lapped with a suitable lapping compoundor they will leak within the first few hours of operation because ofimproper seating.(4) Clean valve seat and faces with drycleaning solvent(item 1, App. F), and dry thoroughly.(5) After lapping valves, remove them from the block andwash valves and block with drycleaning solvent (item 1., App. F).d.Reassembly andInstallation.(1) Install inserts (11, fig. 5-2) and cups (10).(2) Install tappets (6), guides (5); insert exhaust valve(9), and intake valve (4).(3) Install springs (8 and 3), spring seats (7 and 2).(4) Install cylinder head, tapped inspection plate,muffler, and carburetor (para 4-24).5-7
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