Activity Guide Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Table Of Contents Section Title Page Number ENGINE DISASSEMBLY......................................................................................................3 GETTING READY ................................................................................................. 3 REMOVING EXTERNAL PARTS.............................................................................. 5 REMOVING INTERNAL PARTS ................................................................................. 12 INSPECTING OF THE PARTS.............................................................................................16 CLEANING THE PARTS ........................................................................................ 16 CRANKCASE....................................................................................................... 17 VALVES............................................................................................................... 17 VALVE GUIDES..................................................................................................... 18 CAMSHAFT .......................................................................................................... 19 CRANKSHAFT ...................................................................................................... 19 PISTON & CONNECTING ROD ............................................................................... 22 CONCLUSIONS ABOUT ENGINE CONDITION ......................................................................23 REASSEMBLY ..................................................................................................................24 PREPARING THE CRANKCASE................................................................................ 24 INSTALLING THE PISTON ..................................................................................... 28 INSTALLING THE CAMSHAFT ............................................................................... 33 INSTALLING CRANKCASE COVER ........................................................................ 33 INSTALLING THE VALVES ...................................................................................... 35 CYLINDER HEAD................................................................................................... 36 FINAL ASSEMBLY ................................................................................................. 37 TESTING THE ENGINE......................................................................................................38 Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 2 of 38 Ask the instructor for the: Small Engine Rebuilding (Briggs & Stratton) Video Tape Watch the "Disassemble" section of the tape. The video will give you a general idea of the procedure even if your engine is not a Briggs & Stratton. Get the repair manual for your engine. You will be required to look up specifications in the repair manual. ENGINE DISASSEMBLY CAUTION !! Never use excess force when working on the engine. Hammering on parts will cause damage. Clamping unprotected engine parts in the vise will damage the metal surfaces. Always use wooden blocks on each side of the part. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 3 of 38 GETTING READY Remove the fuel from the gas tank. Carefully drain all gasoline into the red gas container marked "Waste Fuel". Use two wooden boards to support the engine above an oil drain pan. Remove the oil plug from the bottom of the engine and drain the oil into the pan. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 4 of 38 Pour the oil into the large oil drum. Get some containers to put your parts in. All the parts you remove must go into containers. (Muffin trays and egg cartons are handy for organizing small parts.) REMOVING EXTERNAL PARTS Remove the fuel line from the gas tank and drain any remaining fuel from the tank. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 5 of 38 Remove the gas tank and pull start housing. Remove the air filter. Remove the muffler. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 6 of 38 In the next step you will be removing the carburetor and governor linkages. Do not proceed until you have taken a digital photograph of the engine to help locate the parts during reassembly. Remove the carburetor. Remove the carburetor and governor linkages. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 7 of 38 Remove the carburetor gasket or rubber O-Ring. Remove the bolts holding the magneto coil to the engine. Disconnect the kill switch wire from the magneto coil. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 8 of 38 Remove the flywheel brake if one is fitted. Remove any screen or other fittings from the flywheel. Ask the instructor to help you determine if the nut holding the flywheel is left or right hand thread. Use an impact gun and socket or special flywheel tools to remove the nut holding the flywheel. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 9 of 38 Use a flywheel puller (special tool) to pull the flywheel off. Ask your instructor for help if you are not sure how to use it. Remove the small shaft key from the crankshaft. Use a spark plug socket and ratchet to remove the spark plug. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 10 of 38 Remove the bolts holding the cylinder head in place. Remove the cylinder head. Remove the cylinder head gasket. Remove the valve spring chamber cover. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 11 of 38 Use fine sandpaper to remove any burrs or rust from the crankshaft. REMOVING INTERNAL PARTS Remove the bolts holding the crankcase cover. Use a soft mallet to tap the crankcase cover off the crankcase. Do not remove any of the internal parts yet. Complete the ** Operating Theory For A 4 Cycle Gas Powered Small Engine ** INFORMATION BOOK. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 12 of 38 Ask the instructor to quiz you on the names of the engine parts. Be prepared to use your partially disassembled engine to explain the four stroke cycle to the instructor. Sign up to have your work checked, then proceed. Instructor's Initial Use the valve spring compressor to compress the valve springs. Remove the retainers holding the valve springs to the valves. Remove the valve springs and valves. Remove oil pump or oil slinger parts if your engine has them. Remove the governor mechanism if your engine has one. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 13 of 38 Rotate the crankshaft until the valve timing marks on the camshaft gear and the crankshaft gear are inline. Remove the camshaft. Remove the valve lifters. Use a hammer and punch to put small locating marks on the connecting rod and connecting rod bearing cap. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 14 of 38 Remove the two bolts holding the connecting rod bearing cap and remove it. Push the piston and connecting rod out of the cylinder. Place the connecting rod bearing cap back on the connecting rod. Be sure that the cap is in its original position. Be sure the marks or tabs line up. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 15 of 38 Carefully remove the crankshaft from the crankcase. Sign up to have your work checked, then proceed. Instructor's Initial INSPECTING OF THE PARTS Watch the video program called "Inspection" on the Small Engine Rebuilding (Briggs Stratton) Video Tape Select the Microsoft Word button at the bottom of this screen. Use Word during the next steps to record your findings as you inspect the engine. CLEANING THE PARTS Wash all engine parts in the parts cleaner. Do not allow parts cleaner to contact the magneto coil or other electrical parts. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 16 of 38 Blow the crankcase dry using compressed air. Be sure to blow compressed air into all the bolt holes. Take care not to lose any parts in the parts washer. CRANKCASE Check the outside of the crankcase for any signs of damage and record your findings. VALVES Use the wire wheel to remove carbon deposits from the stem and face of the valves. Ask for the instructor's help if you are not sure how to do this. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 17 of 38 VALVES Check the faces of the valves and the valve seats for signs of pitting or burning. Record your findings. VALVE GUIDES Record the specification for valve guide wear from the manual. Slide a short piece of rubber onto the valve stem. The rubber must be long enough to hold the valve off the seat when it is placed in the valve guide. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 18 of 38 Blow the valve guides out with compressed air, insert the valve. Use the dial indicator gauge to measure the amount of movement when you move the head of the valve back and forth. Record your measurements. Exhaust _____ Intake ______ CAMSHAFT Inspect the camshaft bearing, surfaces and lobes for signs of wear and or roughness. Record your findings. Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 19 of 38 CRANKSHAFT Inspect the crankshaft bearing journals for score marks or roughness. Use a digital vernier to