What is the engine valve stem

Small valve maintenance & repair

Valves control the flow of fuel vapors into the combustion chamber and the flow of exhaust gases out of the engine. Defective or dirty valves may stick, and pits, cracks, or nicks may form, causing the engine to lose performance and fuel efficiency.

Either way, whether you are having problems with your engine or want to do your routine valve maintenance, make sure you have your step-by-step guide to checking engine valves on hand. Find information for your Briggs & Stratton engines from valve removal to pre-test cleaning.
 

DANGER!: Always read the motor and device manual before you start to commission or maintain your motor or device in order to avoid personal injury and damage to property. See an authorized dealer or contact Briggs & Stratton if you are unsure of how to proceed or if you have further questions. Find all security alerts.

 

If you are looking for a specific valve repair solution, skip to the step-by-step instructions in the section below.

This is how you remove the valves in small engines for testing
How do I check or repair my engine valves?
Valve maintenance: Overlapping valves
Reinstall the valves
Adjust tappet distances & overhead valves

Before you can service or repair the valves, you must remove the engine components that are affecting the engine valve.

Engine valves are removed for testing

To check your engine valves for maintenance or repair, you need to remove them from the engine. Find the engine valve bracket type and follow our step-by-step guide below

This is how you reach the valve chamber

NOTE:: Always wear safety glasses when removing and inserting valves.

  • Step 1: Remove the spark plug and secure the spark plug wire so that it does not touch the spark plug.
  • step 2: Remove the muffler, crankcase breather, and any other components blocking access to the valve chamber.
  • step 3: Remove the socket head cap screws and the other screws from the motor components to access the valve chamber. If necessary, mark the screws to ensure proper assembly later, as the screws can be of different lengths.

Valve removal: vehicle or piston pin retainer

  • Step 1: Remove the spark plug and secure the spark plug wire so that it does not touch the spark plug.
  • step 2: After removing the spark plug and securing the spark plug wire away from the spark plug, adjust the jaws of the valve spring compressor (part number 19063) until they touch the top and bottom of the valve chamber

 

  • step 3: Push the tool in until the upper gripper jaw slides over the upper end of the spring. Tighten the jaws to compress the spring

Step 4: Remove the brackets and lift out the valves, tensioners and springs.

Valve removal: keyhole brackets

Removing the valves for the keyhole brackets will take some patience. Remember that the wedge-shaped slot will help you slide the bracket off the valve stem, even if the bracket is obscured by the valve spring compressor.

  • Step 1: Remove the spark plug and secure the spark plug wire so that it does not touch the spark plug.
  • step 2: Let the upper jaw of the valve spring tensioner slide over the upper end of the valve chamber and the lower jaw between the spring and the bracket. If the motor design does not allow the top jaw to fit over the top of the valve chamber, insert the top jaw into the chamber over the top of the spring so that the spring is between the jaws of the tool
  • step 3: Turn the handle on the valve spring compressor clockwise to tension the spring. Then slide the bracket off the valve by moving it with needle-nose pliers so that the greater part of the keyhole is directly above the stem. Use the pliers to remove the bracket from the valve chamber.
  • Step 4: Using a valve spring compressor, remove the tool and spring from the chamber. Then slowly crank the valve spring compressor to release the tension and remove the spring

Remove the overhead valves

The design of the overhead valves varies from model to model. The parts and maintenance steps for your overhead valve cylinder may differ from the following approach based on the Briggs & Stratton Intek 6-HP OHV single cylinder. The Intek eliminates the need for a valve spring compressor, which simplifies valve removal and installation.

  • Step 1: Remove the spark plug and secure the spark plug wire so that it does not touch the spark plug.
  • step 2: Remove the air filter assembly, fuel tank, oil filler tube, blower housing and recoil starter, muffler guard, muffler, carburetor and other engine parts blocking access to the cylinder head.
  • step 3: Remove the screws from the valve cover using a socket wrench or a nut driver.

 

Then remove the valve cover, if necessary the vent valve unit and existing sealing rings.

  • Step 4: Remove the rocker arm bolts with a socket wrench or nut driver. Then remove the rocker arms and pushrods.
  • Step 5: Remove the valve caps (if present). They sit on valve stems.
  • Step 6: Use your thumbs to push on the spring retainer and valve spring above one of the valves. With the spring compressed, remove the valve spring retainer.

If your engine uses a keyhole bracket, align the large slot in the bracket with the valve stems and slowly loosen the spring so that the stem slides through the large slot. Then repeat the procedure for the other valve.

  • Step 7: Remove the push rod guide bolts and push rod guide.
  • Step 8: Remove the cylinder head bolts and cylinder head by shaking them with your hands. If necessary, loosen the cylinder head with a nylon hammer. Never tear it off as this can damage the head.
  • Step 9: Remove and inspect the valves, guides and seats, following the steps below. The inlet and outlet valves are often made of different steel alloys and may have different colors.

How do I check or repair my engine valves?

Before attempting to repair your valves, take a close look at them. Residue on the valves can help you identify a specific engine problem.

Sticky deposits on the inlet valve are an indication of reduced engine performance; this often happens when the engine has been running on old fuel. Hard deposits on the valves suggest oil is burning, which in turn can have various causes.

Follow the steps below to find the most likely causes of engine valve problems.

  • Step 1: Check the top of the valve to see if it has an irregular seating pattern. The pattern on the top should be even with the valve head and the same thickness all around. In the case of stubborn deposits, clean the valve with a wire brush and solvent; If necessary, soak the parts for several hours to loosen the hard grains.
  • step 2: Run your fingernail or credit card along the cleaned valve stem. If you feel a threshold, the valve stem is worn out and should be replaced. The valve guide may also be worn and need to be replaced.

step 3: Measure the thickness of the valve head, also known as the valve head clearance, using a calliper (part number 19199).

Replace the valve if the margin measures less than 1/64 ".
  • Step 4: Check the surface of the valve top and seat. An uneven wear pattern tells you it's time to replace it, or overhaul the seat and replace the valve.
  • Step 5: Check that both valve springs are straight. Replace either valve spring if it is bent.
  • NOTE: The exhaust valve spring may need thicker wire than the intake valve spring.

Valve maintenance: Overlapping valves

If there is no sign of damage, or if valves are worn out after checking, you can service the valves and their seats so that the valves seal effectively (also known as "valve lapping").

This is how valves are lapped

You can smooth out minor scoring and pitting on the valve top and valve seat to seal the combustion chamber by lapping the valves. As you lap the valves, be sure to check your progress frequently, as the build-up of soot can quickly remove the metal, further damaging the valve or its seat.

  • Step 1: Apply a small amount of valve lapping paste (part number 94150) - a fine but rough paste - to the top of the valve and insert the valve into the valve guide.

 

  • Step 1: Apply a small amount of valve lapping paste
  • Step 2: Wet the end of the suction cup on the lapping tool and place it on the valve head. Twist the valve back and forth a few times in your hands. Lift the tool up, make a 1/4 turn, then turn again.
  • step 3: Clean the surface frequently and check your progress. Lap the valve just enough to create a consistent and even pattern around the valve seat.
  • Step 4: When lapping is complete, thoroughly clean the valves with a solvent to ensure that ALL grinding debris is removed. Residual particles can very quickly damage the valves and other engine components.

 

Reinstallation of the valves after repair & maintenance

Valves with pins or vehicle brackets are reinstalled

Note: When reinstalling valves, wear safety glasses to protect against possible flying springs.

  • Step 1: Place the valve spring in the valve spring compressor and rotate the lever of the tool until the spring is fully compressed.
  • step 2: Insert the compressed spring into the valve chamber.
  • step 3: Brush the valve stem with valve stem lubricant

Then insert the valve stem down through the spring.

Hold the spring towards the top of the chamber and the valve closed.

  • Step 4: If pens are used, insert each one with needle-nose pliers. If automotive mounts are used, insert the mounts into the valve stem groove.
  • Step 5: Slide the spring down until the holder fits around the pen or the car holder. Then pull out the valve spring tensioner.
  • Step 6: Reinstall the crankcase ventilation and other engine components.

So valves with keyhole brackets are reinstalled

Safety glasses are absolutely essential here too. Remember that under tension, a spring can loosen and fly through the air.

  • Step 1: Valves with keyhole brackets do not need an additional bracket. Use a compression tool to squeeze the keyhole bracket and spring together until the spring is tight - the large hole should be opposite the opening in the tool.
  • step 2: Brush the valve stem with valve stem lubricant.
  • step 3: Insert the compressed spring and retainer into the valve chamber
  • Step 4: Insert the valve stem into the holder through the large slot.
  • Step 5: Reinstall the crankcase ventilation and other components.

This is how the overhead valves are reinstalled

  • Step 1: Check that the valve stem and guides are free from dirt and debris. Then lightly cover the valve stems with the valve guide grease and insert them into the cylinder head, being careful to insert the correct valve into each valve guide.
  • step 2: Place the push rod guide on the cylinder head and tighten the mounting bolts with a torque wrench. Coat the threads of the rocker arm pins with a hardening sealant and install the rocker arm pins using a socket wrench.
  • Note: Contact your authorized Briggs & Stratton dealer for proper torque settings for the mounting screws and bolts.
  • step 3: Lubricate the inside diameter of the valve stem seal (if equipped) with engine oil and install the seals on the valve stems. Push them into place.
  • Step 4: Install a valve spring and bracket over each stem.
  • Use both thumbs to compress the spring until the valve stem protrudes through the large end of the keyhole slot. Check that the bracket is firmly seated in the valve stem groove. Repeat this step for the other valve.
    Step 5: Coat the threads of the cylinder head bolts with valve guide lubricant. Install a new cylinder head gasket on the cylinder, insert the bolts into the cylinder and place the cylinder head on top of the cylinder.
  • Step 6: Gradually tighten the cylinder head screws firmly with a torque wrench. Turn each screw a few turns, then move on to the next until each screw is secure. For final tightening, use approximately one third of final torque increments.
  • Note: Refer to your operator's manual for final torque specifications. Uneven tightening is likely to deform the cylinder head.
  • Step 7: Install the push rods through the push rod guides and into the lifters.
  • Push rod type based on engine:
    Single cylinder OHV - Model series 260700, 261700 upper push rod (exhaust) is hollow. On the 28N700, 28Q700, 28U700, 28W700, 287707, 310700, 312700, 313700 model series, the exhaust push rod is marked in red and made of steel.
  • Intek V-Twin OHV - Inlet push rods are made of aluminum.
  • Vanguard V-Twin - All models (except 540000, 610000) exhaust valve lifters are made of aluminum. Model series 540000 and 610000, all pushrods are made of aluminum.
  • Step 8: Install the caps on the valve ends and wipe off any lubrication. Then install the rocker arm assemblies while pressing the rocker arms against the valve cap and push rod.
    Installation of rocker arm units
  • Step 8: Install the caps on the valve ends and wipe off any lubrication. Then install the rocker arm assemblies while pressing the rocker arms against the valve cap and push rod.

Adjust tappet distances & overhead valves

This is how the ram distances are adjusted

Because lapping the valves removes some material from the valve surface and valve seat, after lapping and reinstalling the valves, you may need to adjust the tappet clearances - the clearance between the valve stem and the tappet. Check with your local Briggs & Stratton dealer for the correct valve lift clearance for your engine.

Step 1: With each valve installed in its proper guide in the cylinder, rotate the crankshaft (clockwise as viewed from the flywheel end of the crankshaft) straight up to the center. Both valves should be closed. Then turn the crankshaft past top dead center until the piston is 1/4 "below the top of the cylinder.
Note: This procedure should be repeated for each cylinder in two-cylinder opposed piston engines and two-cylinder V-twin engines.
Step 2: Check the distance between each valve and its stem using a feeler gauge
step 3: If the clearance is insufficient, remove the valve or file the end of the valve stem square to increase the clearance. Check the length often as it is easy to remove too much metal.
Step 4: When the individual valve parts have been thoroughly cleaned, lubricate the valve stems and guides with valve guide grease.Then make sure that there is NO grease on the ends of the valve stems or tappets.

This is how overhead valves are adjusted

  • Step 1: Release the brake spring. Then turn the flywheel to close both valves.
  • step 2: Insert a narrow screwdriver into the spark plug hole and touch the piston. Turn the flywheel clockwise past the exact center until the piston has moved 1/4 "down. Use the screwdriver to measure the radius of movement of the piston.

 

  • PLEASE NOTE: This procedure must be performed for each cylinder in two-cylinder V-twin engines.
  • step 3: Check the valve clearance by placing a feeler gauge between the valve head and the rocker arm. The distances are different for the two valves and typically range from 0.002-0.004 "to 0.005-0.007".
  • Step 4: Adjust the spacing as needed by turning the tilting screw. When the adjustments are complete, tighten the dump nut.
  • Step 5: Install the valve cover, using new gaskets as necessary, and make sure the cover is securely in place.