TM 5-4930-227-14(c) Finish the counterbore in the cylinderblock to provide the correct bore-to-insert inter-ference. Chill the insert with dry ice and, usinga pilot driver, tab the insert into place withlight blows. Peen the insert to anchor in place.(d) Reface the insert, if necessary, to makeits seat concentric with the valve stem bore. Checkconcentricity with a dial indicator.(e) Grind valve in seat to form a gas-tight seat.d. Regrinding Valves.(1) Using a valve seat grinding tool, grindthe seats at a 45° angle and then grind thevalve faces at a 45° angle with a valve refacergrinder.(2) Valves must be lapped with a suitablelapping compound or they will leak within thefirst few hours of operation because of improperseating.(3) Clean valve seat and faces with an approved cleaning solvent and dry thoroughly.(4) After lapping the valves, remove themfrom the block and wash the valves and blockwith an approved cleaning solvent.e. Reassembly. Refer to figure 6-4 and reas-semble valves.f. Installation.(1) Install tappet cover plate (para 6-3).(2) Install cylinder head (para 6-2).(3) Install muffler (para 3-31),(4) Install carburetor (para 3-28).(5) Install engine (para 3-17).6-5. Engine Base and Oil Pumpa. Removal.(1) Remove the engine (para 3-17).(2) Refer to figure 6-5 and remove theengine base and oil pump.b. Disassembly. Refer to figure 6-6 and disas-semble the engine base and oil pump.c. Cleaning, Inspection, and Repair.(1) Clean all parts with an approved clean-ing solvent and dry thoroughly.(2) Inspect all parts for cracks, breaks, andother damage.(3) Inspect all hardware for damaged orstipped threads.(4) Replace a damaged or defective part.d. Reassembly. Refer to figure 6-6 and reas-semble the engine base and oil pump.e. Installation.(1) Refer to figure 6-5 and install the en-gine base and oil pump.(2) Install the engine (para 3-17).Figure 6-4. Valves, removal, disassembly, reassemblyand installation.1 Lock (4)7 Rotator2 Spring seat8 Spring3 Spring9 Exhaust valve4 Intake valve10 cup (2)5 Guide11 Insert6 Tappet (2)12 Crankcase6-3
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