Small Engine Disassembly and Reassembly Briggs and Stratton 4 Cycle Page 2 of 38 Ask the Instructor for The

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.

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.

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 measure the diameter of the journals.

Record the values as shown.

Journal 1: ______Journal 2: ______Journal 3: ______

Look up the crankshaft bearing journal specifications from the shop manual and record the values.

How do your readings compare to the specifications?

Write a paragraph describing the condition of the crankshaft and state whether or not it should reinstalled in the engine.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 20 of 38 Note the position of the connecting rod bearing cap.

Remove the connecting rod bearing cap from the connecting rod.

Use the shop manual to look up the torque specification for the bolts holding the connecting rod bearing cap.

Record the value.

Ask the instructor for a piece of Plastigage.

You will use the Plastigage to measure the clearance between the crankshaft journal and connecting rod.

Break off a piece of plastigauge, the length should be the same as the width of the crankshaft journal.

Position the connecting rod on the crankshaft journal as shown in the picture.

Put a piece of plastigauge on the journal.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 21 of 38 Be careful not to rotate the crankshaft while you install the bearing cap.

Use a torque wrench to tighten the conntecting rod bolts to specifications.

This will squeeze the plastigage between the connecting rod and crankshaft.

PISTON & CONNECTING ROD

Remove the bearing cap.

Use the envelope from the Plastigage to measure the width of the Plastigage strip on the crankshaft.

The thinner the Plastigage strip the wider the clearance between the connecting rod and crankshaft.

Acceptable clearance is .001" to .002"

Record the value for your engine.

CAUTION !!

In the next step you will be removing the piston rings. They break very easily, do not stretch them any farther than required to remove them.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 22 of 38 Use a piston ring expander to remove the rings from the piston.

Do not overstretch the rings!

Be sure to note the order and direction of the rings so they can be installed exactly the same.

Remove any carbon which has built up in the piston ring grooves.

Check that the oil holes in the lower ring groove are clear.

With the connecting rod in one hand and the piston in the other, pull up and down on the piston.

If you feel any play, the piston or piston pin is worn and must be replaced.

Record your findings.

Check the piston and skirt for any sign of scoring, cracking or damage.

Record your findings.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 23 of 38 CONCLUSIONS ABOUT ENGINE CONDITION

Create a short report.

List your measurements and observations.

Describe the generall condition of the engine.

REASSEMBLY

Watch the video program called "Assembly" on the Small Engine Rebuilding (Briggs & Stratton) Video Tape

CAUTION !!

Be sure to coat all engine parts with clean oil before assembly.

Parts not oiled will be damaged during initial start up.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 24 of 38

PREPARING THE CRANKCASE

If no problems have been found with the valves, you will use lapping compound to lap the valves onto the seats.

The lapping compound and tool can be found in the botton of the Sioux Valve grinding machine.

Put a small amount of lapping compound on the face of the valve.

Do not allow any of the lapping compound to get on the stem of the valve!

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 25 of 38 Place the valve into the valve guide. Do not allow lapping compound to get into the valve guide!

Use the lapping tool to spin the valve so the lapping compound refinishes the valve face and seat.

Clean the crankcase and valves in the parts washer.

Blow the crankcase dry using compressed air.

Be sure to blow out the valve guides.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 26 of 38 Check the rubber lip of each crankshaft oil seal for signs of wear, if required replace it.

Be sure to put lots of oil on the rubber lip of the oil seals where they contact the rotating crankshaft.

Oil all of the crankshaft bearing journals.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 27 of 38 Install the crankshaft in the crankcase.

INSTALLING THE PISTON

Wipe the cylinder walls with a clean cloth, then oil them thoroughly.

Unpack the new piston rings (if provided) and determine which ring belongs in which groove.

Also note which side of the ring is to face up.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 28 of 38 Put each of the upper piston rings into its groove and use a feeler gauge to measure the side clearance of the ring.

Record the ring side clearance:

Record the specification for ring side clearance from the manual.

Is the ring side clearance within specifications?

Position each of the compression rings near the bottom of the cylinder and use the feeler gauge to measure the gap between the ends of the ring.

Record the End Gap for each ring.

A gap which is too large indicates a worn cylinder or ring. A gap which is too small will not allow for expansion and will cause the piston to sieze in the cylinder.

Compare your readings to the specifications in the manual.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 29 of 38 The first ring to go on the piston is the oil ring. If your engine uses a three part oil ring, follow the directions below.

Use the piston ring installation tool to install the compression rings.

Position the rings so the gaps of the rings are staggered.

Put lots of oil on the piston, piston rings and piston pin.

You will use a piston ring compressor to install the piston into the cylinder.

Pressing the lever on the compressor unlocks it for adjustment.

You will need a 1/4" ratchet and extension to adjust the compressor.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 30 of 38 Install the piston ring compressor on the piston.

Make sure that the dimpled end of the compressor is pointing toward the connecting rod.

Use a ratchet and extension to tighten the compressor onto the piston.

Position the crankshaft so the connecting rod journal is at the bottom of its travel.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 31 of 38 Slide the piston and connecting rod into the cylinder. The compressor should be resting on the engine.

Some pistons may have locating marks, the manual should tell you which side of the engine the mark should be facing.

Be sure the ring compressor is tight on the piston.

Use a hammer handle to tap the piston into the cylinder.

Guide the connecting rod onto the crankshaft journal as the piston moves downward.

Take care not to damage the journal of the crankshaft.

Oil the connecting rod bearing cap and place it on the connecting rod.

Make sure the marks you made earlier line up with each other!

Install the bolts and tighten them finger tight for now.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 32 of 38 Find the torque setting for the connecting rod nuts in the manual. Record the value.

Use the inch pound torque wrench to tighten the nuts. (Ask the instructor if you are not sure how to use the torque wrench.)

After the nuts are tight try to turn the crankshaft.

You should be able to turn the crankshaft if everything has been assembled correctly.

INSTALLING THE CAMSHAFT

Lubricate the valve lifters and install them.

Lubricate all parts of the camshaft and install it.

Remember that for correct valve timing the marks on the camshaft gear and crankshaft gear must line up.

Instructor's Stop here until the instructor has checked your work.

Initial

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 33 of 38

INSTALLING CRANKCASE COVER

Install any other oil pumps, governors etc.... as shown in your manual.

Install a new crankcase cover gasket.

Oil the bearing surfaces in the crankcase cover.

Install the crankcase cover.

Install and tighten the crankcase bolts.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 34 of 38 Position a dial indicator on the end of the crankshaft. Move the crankshaft back and forth.

Use a dial indicator to check the crankshaft end play. Record it.

Look up the specification for end play and compare to your measurement.

INSTALLING THE VALVES

Lubricate the valve guides.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 35 of 38 Lubricate the stems of the valves, then insert them in the valve guides.

Use the valve spring compressor to compress the valve springs and install the springs and retainers.

CYLINDER HEAD

Look up and record the torque setting for the cylinder head bolts.

Record the value.

Install a new head gasket.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 36 of 38 Install the cylinder head and torque the bolts to specifications.

Follow the tightening sequence shown in the manual.

FINAL ASSEMBLY

[Need a redirector for understanding ignition.]

Install the ignition parts.

Look up and record the ignition breaker point

gap. (point type ignitions only)

Set the ignition breaker point gap to specifications. (point type ignitions only)

Install the flywheel key into the crankshaft.

Install the flywheel along with any washer and other parts.

Start the nut by hand, then use the impact gun to tighten the nut holding the flywheel.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 37 of 38 If the air gap between the ignition coil and the magnet is adjustable you should adjust it to specifications.

Install the rest of the parts on the outside of the engine. Be

very careful to install the carburetor linkages correctly.

Install the spark plug.

CAUTION !!

Do not attempt to start the engine without the instructor's approval.

Fill the crankcase to the correct level with oil.

Fill the fuel tank 1/4 full with gas.

TESTING THE ENGINE

Design and build some type of mounting for the engine so it is secure when you test run it.

Stop here until the instructor has checked your work. Instructor's Initial

Connect an exhaust hose to the engine and start it up.

Small Engine Disassembly and Reassembly Briggs And Stratton 4 Cycle Page 38 of 38