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Spark

(Cont.)

The

spark

can

checked

using

spark

tester.

Simply

connect

the

spark

plug

lead

the

tester

and

ground

the

clamp

the

engine.

Pull

the

rewind

starter

engage

the

starter

and

check

for

spark

output

the

window.

Ignition System

The ignition system provides a high voltage spark in
the combustion chamber at the proper time.

Two types of ignition systems

Battery

Magneto

Battery

Battery systems transforms the battery voltage and
fires the spark plug at the correct time.

Magneto

Magneto systems must produce the current,
transform the voltage and time the spark plug.

Most small engines use the magneto system

Two types of magneto systems:

Breaker point ignition

Solid state (electronic) ignition

Breaker point ignition

Older system. Most manufacturers have replaced
them with solid state.

Uses a set of points to break the primary circuit.

Solid state ignition

Uses a transistor to break the primary circuit.

Содержание 303447

Страница 1: ...Co Sm Rev ommer mall En v 6 12 rcial Eq ngine T quipm Troubl ment Se leshoot ervice T ting Trainin ng ...

Страница 2: ...ure reference materials to be used one your return back at your workplace If you still have questions or want further explanations clarifications talk with other attendees here and or the Training Instructor for additional explanation or discussion Make the most productive use of your time in this program The clearer the understanding you have of the information provided the more effective you bec...

Страница 3: ...one should leave without getting their questions asked Small engines are an important component of many of the machines that are needed to maintain turf areas and perform other maintenance jobs Small engines are very reliable and with proper care and maintenance will last a long time However while they are dependable components when they do not perform as needed they can be one of the most frustra...

Страница 4: ...s can be used when either of these two situations are encountered Let s examine how to identify the problem you may face with a small engine If you have a no start issue or a poor performance issue there are some Facts that we need to understand when troubleshooting these engines We will look at the FACTS F Fuel A Air C Compression T Timing S Spark For the engine to run properly we need to have Fu...

Страница 5: ...e It may be on the engine housing on the valve cover or on an engine side plate These numbers may include a model type and code Briggs and Stratton for example provide the following information through their numbering system Model provides engine configuration information Type list specific parts paint color OEM information Code provides specific manufacturing date and plant information ...

Страница 6: ... 5 Vertical Shaft Vacu Jet Carburetor Pneumatic or Mechanical Governor 6 Vertical Shaft 7 Vertical Shaft Flo Jet Carburetor Pneumatic or Mechanical Governor 8 Vertical Shaft Flo Jet Carburetor Mechanical Governor 9 Vertical Shaft Pulsa Jet Carburetor Pneumatic or Mechanical Governor 0 Plain Bearing DU Non Flange Mount 1 Plain Bearing Flange Mounting 2 Sleeve Bearing Flange Mounting Splash Lube 3 B...

Страница 7: ... engine with an electric started and gear drive alternator The type number list specification normally related to the OEM options and requirement This included the engine paint color governed speed and OEM information The code tells us that this engine was built June 12 2001 on line 1 plant 1 All of this information is needed to properly test adjust and repair the engine ...

Страница 8: ...he air fuel mixture is compressed The spark plug fires starting combustion Combustion causes a rapid rise in temperature The increased temperature causes pressure to increase which produces a force on the piston The connecting rod and crankshaft converts the linear motion to rotary motion The burnt gases are expelled from the engine Do not confuse these events with the four strokes events of a fou...

Страница 9: ... A four stroke engine also known as four cycle is an internal combustion engine in which the piston completes four separate strokes intake compression power and exhaust during two separate revolutions of the engine s crankshaft and one single combustion cycle ...

Страница 10: ...d the volumetric efficiency of the engine Detail Piston moves from TDC to BDC Intake valve open Exhaust valve closed Piston movement causes an area of low pressure to develop in the combustion chamber Higher ambient atmospheric pressure forces air through the intake system In gas carbureted engine the air picks up the fuel as it passes through the carburetor In gas fuel injected engines the gas is...

Страница 11: ...r mixture into the combustion chamber of the cylinder head Detail Piston moves from BDC to TDC Intake valve closed Exhaust valve closed Piston movement reduces the volume of the combustion chamber increases pressure Pressure of compression 60 to 80 psi Any pressure that escapes reduces the performance of the engine 360 degrees of rotation ...

Страница 12: ... density of the fuel air mixture and allows for a more efficient combustion process and higher power output Compression ratio is a comparison between the volume of the cylinder at BDC to the volume of the cylinder at TDC Ratios of 6 to 8 1 are common for gasoline engines and 18 to 20 1 for Diesel engines ...

Страница 13: ...n moves from TDC to BDC Intake valve closed Exhaust valve closed Rapid burning causes rapid rise in temperature Rapid rise in temperature causes increased pressure Pressure induces a force on the piston Force on piston produces torque on crankshaft 540 degrees rotation EXHAUST stroke during the exhaust stroke the piston once again returns to top dead center while the exhaust valve is open This act...

Страница 14: ...impulse every other revolution These engines are more popular than 2 cycle They do require more parts that 2 cycle Less exhaust emissions than 2 cycle Typical lubrication system restricts angle of operation due to either splash lube from the sump or pressure lubricated pulling oil from the sump They are also normally more durable than 2 cycle ...

Страница 15: ...exhaust port is exposed Cylinder pressure causes gasses to flow out the port Further movement of the piston and the intake port is exposed Crankcase pressure causes air fuel oil to flow into the combustion chamber As the piston moves towards the cylinder head the intake and exhaust ports are covered and the air fuel oil charge is compressed As soon as the intake port is covered further piston move...

Страница 16: ...r Operate in multi positions Shorter expected life Earlier we mentions the FACTS required for engine operation Let s examine how to identify the problem you may face with a small engine This will require a look at the Facts that are needed to make the engine run and run properly Let s begin with Fuel When looking at FUEL there are a few questions to ask Does it have any fuel Is the shut off valve ...

Страница 17: ...ttainment zones Nonattainment zone areas of the country that exceed ozone levels There are Two common additives Alcohol Methyl Tertiary Butyl Ether MTBE Alcohol Two types Ethanol distilled from grains and sugar containing plants Methanol distilled from natural gas The addition of alcohol to gasoline increases the available oxygen during the combustion process Up to 10 ethanol acceptable for most s...

Страница 18: ...from Kohler allows the user to quickly and effectively test fuel for alcohol content To check alcohol content add water to the tester up to the water line Then add gasoline up to the neck of the tester Put on the cap and shake The water will mix with the alcohol while the gas and the water will remain separated Set aside for a couple minutes and then note where the water fuel separation line is Co...

Страница 19: ...ir filter is to deliver both high airflow and dirt protection Both air flow and dirt protection are critical to engine performance The basic types of air filters are Oiled foam this is a foam type material which is oiled to capture dirt particles and keeps them from entering the engine These types of filters are normally cleaned and re oiled as a maintenance procedure Paper type filters used a ple...

Страница 20: ...recommend using compressed air when cleaning filters If you choose to you compressed air to clean a paper element filter it is recommended that the filter be cleaned with low pressure air This reduces the likelihood that the paper element is damaged during the cleaning process A recommendation is to attach an air pressure regulator to the hose that is used for filter cleaning Setting the regulator...

Страница 21: ...ondition of the intake and exhaust valves piston rings and cylinder walls and head gaskets or other sealing components Preparing the unit for the test Remove all the Sparkplug s Connect Battery Charger if equipped with electric start On single cylinder engine with compression release engine may need to be rotated backwards Refer to the engine manufactures documentations Crank engine a consistent n...

Страница 22: ...ssion stoke May be mechanical Engages during starting and disengages after the engine reaches operating speed Compression release will affect the results from a compression test There are some problems related to compression in gas engines Two possible problems Inadequate compression Excessive compression Inadequate compression Commonly caused by leaks Excessive compression Carbon Buildup Harder s...

Страница 23: ...plug fires Multiple pressure fronts collide Sometimes called knocking spark knock or pinging Causes large pressure differentials in the combustion chamber Can cause engine damage Causes Increased compression High temperatures Lean fuel air mixture Advanced ignition timing Lower octane fuels Prevention Remove any cause ...

Страница 24: ...ncreases internal temperature Will cause engine parts like pistons connecting rods and crankshafts to fail Causes An overheated spark plug Glowing carbon deposits Overheated exhaust valve A sharp edge in the combustion chamber or on top of a piston Sharp edges on valves that were reground improperly A lean fuel mixture There is another test that can be performed to evaluate the condition of the en...

Страница 25: ...ide information on where the problem is Air leaking out of the exhaust indicates a leaking exhaust valve Air leaking from the air filter indicates a leaking intake valve Air leaking from the crankcase indicates leaking compression rings or head gasket NOTE There will always be air leaking for the crankcase If this is the gauge shows excessive leakage and the only place you hear air escaping is fro...

Страница 26: ... to improve its mechanical properties This helps to tolerate high impact and wear resistance of the stem end Valve hard facing Changes or modifies wear and heat characteristics of the valve face Valve stem surface treatments Changes or modifies wear characteristics of the valve stem Valve head design Interference interface angle Valve seat angle and the valve seat angle are slightly different Prev...

Страница 27: ...igh te de a predic self and the uminum bra ts valve face t etal seal sert but not surfaced oveable end withstand p d mechanic lliptical sha when cold at piston pin ston en hot of the valve s in temper of foreign m emperature ctable and c e valve stem ass or sinte to seal com always d of the com pressure flu cal loads ape n bore expa es rature chem material and es consistent c m ered iron mbustion ...

Страница 28: ...ng groo cont s on pins are st be orient are used in n to crankca oves ves are mac o hold the r s are the are es ance betwee erhaul the g ove cleaner offset tated correc oil ring gro ase chined groo rings eas of the p en the rings grooves sho r ctly in bore oove to allow oves in the piston betw s and the ri ould be clea w excess piston ween the ng lands aned with ...

Страница 29: ... rings on each piston Compression Subject to the greatest amount of chemical corrosion and highest temperatures Transfers 70 of combustion heat from piston to cylinder walls Wiper ring Meters oil film on cylinder walls Must be installed correctly Oil ring Constructed of two thin rails with holes or slots cut in between Has the highest pressure against the cylinder wall of the three rings Cylinder ...

Страница 30: ...engine to operate properly Most often this is affected by a bad flywheel key Spark Most often affected by a bad spark plug Remove the spark plug and check for deposits These can be cleaned with a wire brush The gap of the spark plug can also be a factor The gap should be set as recommended by the manufacture If the gap is correct then check the spark output ...

Страница 31: ...tion systems Battery Magneto Battery Battery systems transforms the battery voltage and fires the spark plug at the correct time Magneto Magneto systems must produce the current transform the voltage and time the spark plug Most small engines use the magneto system Two types of magneto systems Breaker point ignition Solid state electronic ignition Breaker point ignition Older system Most manufactu...

Страница 32: ... Magneto Ignition System As magnets in flywheel rotate past the magneto the points close The magnetic flux of the magnets in the flywheel induces a current in the primary coil With current flowing in the primary circuit a magnetic field develops around the primary coil This magnetic field also surrounds the secondary coil As the flywheel continues to rotate the breaker points open ...

Страница 33: ...lows across the secondary coil which induces a current in the secondary coil Because there is a 60 1 ratio of windings in the two coils the voltage is transformed to the 10 000 and 15 000 volts needed to fire the spark plug Magneto Ignition system As long as the flywheel is rotating and the ignition switch is on the spark plug fires every time the magnets move past the magneto ...

Страница 34: ...er Point and Solid State Ignition System The solid state electronic ignition system replaces the mechanical points switch with an electronic switch A trigger coil senses the presence of the magnets and opens the primary circuit ...

Страница 35: ...te way to do it One method is to use a Vibra Tach Another is to use a Photo Tach The key is that RPM both Low and High is properly set When working with multiple cylinder engines sometime the performance problem may be related to only one cylinder To determine which cylinder is at fault perform a Cylinder Cancel Test ...

Страница 36: ...em ie Piston hitting the head Crankcase Breather Another component to look at is the Crankcase Breather Maintains pressure in the crankcase at less than ambient pressure to assist in the control of oil consumption Excessive engine blowby renders the breather useless Old engines vent to the atmosphere New engines vent to the carburetor Routine Maintenance Default to Manufactures Recommendation Ever...

Страница 37: ...l cap cover with aluminum foil and seal with rubber band 4 Fog the engine 5 Clean and re gap the spark plug End of season Maintenance Cont 6 Service the air cleaner 7 Seal the combustion chamber Pull rewind rope until the piston reaches top of the cylinder on the compression stroke you can tell by the increased tension on the rope 8 Remove dirt and debris and cover the engine ...

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