John deere x304 repair manual

Oil Plug. Oil Pump Cover Cap Screws. Rocker Arm Stud Bolts. Rocker Cover Cap Screws. Stator Coil Cap Screws. Vacuum Gauge JT Used to check engine crankcase vacuum. Drill Bit 6. Throttle adjustment. Lapping Tool - - - Valve lapping Dial Indicator - - - Automatic compression relief test, valve inspection, crankshaft end play.

Reaming Tool 7. Pressure Gauge Assembly JT Used to read engine oil pressure when performing engine oil pressure test. Current Gun JT Used to check starter performance. Other Material Part No. Tool Use Theory of Operation: A positive displacement gerotor pump is used to pressurize the lubrication system.

The lubrication system is protected by an oil pressure relief valve, low oil pressure switch, and an oil filter with bypass valve. The oil pump draws oil from the sump through the pick-up screen. Pressure oil from the pump flows through the pump outlet passage past the oil pressure relief valve. If the oil pressure exceeds kPa 43 psi , the relief valve opens allowing oil to return to the sump. The relief valve is not adjustable.

Pressure oil flows past the relief valve to the oil filter. The filter contains a bypass valve which opens at An oil pressure switch mounted above the oil filter turns on a warning light if oil pressure is below 98 kPa Filtered pressure oil flows through a passage in the oil sump to the crankshaft main bearing PTO side. Drilled passages in the crankshaft distribute oil from the main bearings to the connecting rod journals and crankshaft main bearings flywheel side.

A drilled passage in the connecting rods allows oil from the connecting rod journal to lubricate the piston and cylinder walls. Eventually these oil particles collect into a liquid state again in the lower portion of the rocker arm chamber. A small return passage is provided to return this liquid state oil back into the crankcase. The breather creates a negative pressure in the crankcase which prevents oil from being forced out of the engine through the piston rings, oil seals or gaskets.

Cylinder blow- by gases go through the crankcase to the breather chamber. They are drawn into the engine side of the air cleaner through the cylinder head and mixed with the clean air flow as part of the emission control system.

The camshaft gear, camshaft, tappets, coolant pump gear, governor gear, oil pump gear, and crankshaft gear are lubricated by oil splash generated by the internal moving parts during operation.

To create fuel flow through the carburetor, there must be a pressure differential between the fuel bowl and the throat of the carburetor. Venturi Air goes through the carburetor throat.

When it reaches the venturi, the air speed is increased and the air pressure Is decreased. The venturi is a restriction in the carburetor located between the choke and throttle valves. The restriction causes air to speed up resulting in a lower than atmospheric pressure area in the carburetor throat.

Since fluids flow from areas of higher pressure to areas of lower pressure the resulting pressure differential between the fuel bowl high pressure and the venturi low pressure , causes fuel to be pushed flow from the fuel bowl to the venturi. There are two types of bowl venting: external and internal. Note: Late model carburetors are internally vented to meet emissions standards. Externally vented carburetors exert direct atmospheric pressure from outside of the air filter onto the fuel in the bowl.

Internally vented carburetors exert indirect atmospheric pressure from inside the air filter, ahead of the choke valve, onto the fuel in the bowl. Fuel Bowl and Float The fuel bowl is the fuel reservoir for the carburetor. The float maintains the level of fuel in the bowl while regulating the fuel flow to match the demands of the engine by controlling the inlet float valve needle.

Control Valves MX The carburetor has two control valves: throttle valve and choke valve. The throttle valve is operated by the throttle lever and controlled by the governor.

The throttle valve controls how much air and fuel enters the cylinder s. The choke valve, located before the venturi, creates a restriction when closed. The function of the choke valve is to increase the pressure differential between the fuel bowl and the venturi area.

In some engines, a primer is used in place of a choke valve to push fuel into the venturi. Concept of Idle Governed engines are designed to maintain a specific engine speed.

Governed engines with no load PTO disengaged, drive in neutral are said to be at "idle" regardless of engine speed. When the operator selects the low speed position with no load, the engine is at low idle. When the operator selects the high speed position with no load, the engine is at high idle. Idle Circuit MX The idle circuit, on a governed engine, delivers air and fuel primarily when the engine is not under load PTO disengaged, drives in neutral. Fuel flow enters the idle circuit from the main jet but is metered by the idle jet.

The fuel is then emulsified with air passing through an air bleed and combining with the fuel. The pilot opening is used for low idle operation. The pilot opening is located between the closed throttle plate and the intake manifold. The opening has a pilot screw that allows for some adjustment. This adjustment primarily affects low idle. When the governor slightly opens the throttle valve for high idle or when a load is applied, the transitional bypass openings are exposed.

Once the engine is under a heavier load, the throttle valve is opened beyond the transitional bypass openings. At this point the carburetor receives fuel primarily from the main circuit.

Main Circuit MX The main circuit, on a governed engine, is used only when the engine is under load. Fuel flows from the fuel bowl through the fixed main jet into the main circuit. Air enters through a metered orifice air-bleed and emulsifies mixes air and fuel as it travels up the emulsion tube to the venturi. Emulsification is an important process to properly atomize the fuel and promote efficient combustion.

Fuel Shutoff Solenoid The fuel shut-off solenoid reduces fuel flow to the main circuit. The function of the fuel shut-off solenoid is to minimize after-bang. At engine start up, the fuel shut-off solenoid is energized and the poppet retracts from the seat in the bowl, allowing fuel to enter into the main jets. To bench test the fuel shut-off solenoid, apply light pressure to the tip to simulate its mounting in the fuel bowl and apply 12 volts DC.

If the needle retracts, the solenoid is working. Verify the tip is secured to the plunger. Are battery cables loose or dirty? Yes: Tighten or clean. No: Go to next step 2. Is battery fully charged? Yes: Go to next step No: Charge Battery.

Is key switch working correctly? Yes: Go to next step. No: Test Switch, Replace as needed. Is starter motor defective? Yes: Repair or replace. No: Go to next step. Is alternator defective? Has engine seized? Yes: See engine Repair Section. No: Go to next step 7. Is starting motor or solenoid defective? Is there a open circuit in wiring? Is the fuel shutoff solenoid operating correctly? No: Repair or replace. Is the fuel filter or fuel lines clogged?

Yes: Clean or replace as necessary. Is the fuel pump operating correctly? No: Clean or replace as necessary. Is their water in the fuel? Yes: Drain and replace fuel. Are the valves adjusted properly? No: Adjust valve clearance. Does engine have correct compression? No: Check for seized or burned valves, broken piston rings, or worn cylinder Is air sucked through carburetor or intake manifold flanges? Yes: Tighten manifold flange nuts or replace damaged gasket.

Yes: Repair. Is there a strong blue spark? No: Repair or replace ignition module. Are sparks jumping from produced between high tension lead and ignition block. Check high tension lead, ignition coil air gap, pulser coil. The engine may start to rotate at any time. Keep hands away from moving parts when testing. Is engine compression good? No: Check piston rings and cylinder for wear.

Inspect Cylinder head. Make starting attempts a number of times, remove spark plug and observe electrodes. After starting attempts, are spark plug electrodes wet? Yes: Check for excessive use of choke, plugged air cleaner, float bowl level too high. No: Go to next step Engine Runs Erratically 1.

Is fuel delivery correct? No: Check for defective fuel pump or plugged fuel lines or fuel tank. Is fuel present in carburetor? Is there contamination in fuel lines, or fuel tank? Is unusual smoke emitted out of muffler? Yes: Check choke. Does engine rpm drop or engine stall at a certain point when throttle is gradually opened by hand? Yes: Check for obstruction or plugged passage in carburetor. No: Go to next step 4.

Are valve clearances set correctly? No: Adjust valves. Oil Consumption Is Excessive 1. Check for oil leaks, high oil level, clogged breather valve, plugged drain back hole in breather, Is oil viscosity correct?

Yes: Repair as required. Is compression correct? No: Check for worn, stuck, or broken piston rings, or worn cylinder bore. Low Oil Pressure 1. Is oil level correct? No: top off oil to correct level. Is oil filter clogged? Yes: Replace Oil Filter. Is oil of correct viscosity? No: Change engine oil. Is oil relief valve worn?

Yes: Clean, adjust or replace relief valve. Is oil pump operating correctly? No: Replace oil pump. Is there fuel in the oil?

Keep spark plug as far away from the plug hole as possible. Gasoline spray from the open cylinders may be ignited by ignition spark and cause an explosion or fire. Is oil pump screen clogged or pick up tube cracked? Yes: Clean screen and repair or replace pick up tube. Is there excessive crankshaft or rod bearing clearance? Yes: Regrind crankshaft and install undersize connecting rods.

Yes: Replace valves and head. Contamination in Crankcase 1. Is there fuel in the crankcase? Yes: Check for broken or seized piston rings or worn cylinder. Check for worn or seized exhaust valve. Is there water in the crankcase? Yes: Check to make sure that crankcase breather is working correctly. Is there a click sound from the starter solenoid? No: Repair starter motor. Check that all starting conditions are met?

No: Make sure all starting conditions are met. Yes: Clean and tighten. No: Charge battery. No: Repair or replace key switch 6. Is engine seized? Yes: See Engine Repair section. No: Go to next step Starter Rotates Slowly 1. Yes: Clean and Tighten. No: Go to next step 5. Is there fuel? If starting motor does not stop rotating by turning ignition switch to Off position, disconnect negative - lead from battery as soon as possible.

No: Add fuel, check fuel lines. Is fuel line plugged? Yes: Clean fuel line and fuel filter. Check for fuel supply at carburetor. Does the fuel solenoid open? No: Test solenoid and power to solenoid. See Electrical section. Is the main jet clogged? Yes: Disassemble and clean jet and passages.

Is the needle valve stuck closed? Yes: Check for old or gummy fuel. Clean carburetor. Check valve tip. Is the air filter clean? No: Clean or replace air filter. Is the choke plate opening properly? No: Adjust choke cable. See choke cable and throttle cable adjustment. Check passages in carburetor.

Are passages open and free of debris or varnish? No: Clean carburetor. Check main jet. Is main jet dirty? Yes: Clean carburetor. Check main jet for proper size. Is correct main jet used? No: Replace main jet. Engine Idles, Runs loaded or not Then Stops 1. Is the fuel system properly vented? No: Check fuel cap if vented cap is used. Check vent lines to carburetor for kinks, or collapsed or weak areas.

Is dirt in the bowl being sucked into main jet? Yes: Check float bowl for dirt or corrosion, clean bowl. Check main jet for loose debris. Engine Does Not Idle Properly hunts or surges 1. Check to see if the problem is governor or carburetor: Hold the throttle plate closed to force engine to idle.

Does the engine continues to run? If the engine stalls - suspect idle circuit. Yes: Check governor for proper operation. No: If engine stalls, check idle circuit. This is only true when you do not have the resources and tools available for when that time comes! This manual will easily pay for itself on the first oil change, spark plug change, or air filter change that you perform! The manual includes pictures and easy to follow directions on what tools are needed and how the repair is performed.

Just imagine how much you can save by doing simple repairs yourself. Many people buy this manual just to have it around for when the inevitable happens. Sooner or later, maintenance will need to be performed. No: Go to next step 5. Check to see if the problem is governor or carburetor: Hold the throttle plate closed to force engine to idle.

Does the engine continues to run? If the engine stalls - suspect idle circuit. No: If engine stalls, check idle circuit. Clean carburetor with attention to idle circuit passages. Check float bowl for dirt or corrosion. Check for dirt between needle valve and seat.

Is dirt or debris present? Is the needle valve stuck closed? Yes: Check for old or gummy fuel. Clean carburetor. Check valve tip. Check air passage and pilot jet for debris or varnish. Is there debris in the idle air bleed or pilot jet? No: Adjust choke cable. See choke cable and throttle cable adjustment. Check passages in carburetor. Are passages open and free of debris or varnish? No: Clean carburetor. The majority of fuel system problems are related to stale or improper fuel or dirt.

This section is to help you diagnose fuel system problems. Initial Checklist. No: Check fuel cap if vented cap is used. Check vent lines to carburetor for kinks, or collapsed or weak areas. Verify the quality of the engines mechanical and electrical systems.

Attempt to manually control the throttle at low and high idle to determine which system is causing the surge. If the engine speed can be held constant check the governor system.

If the engine surge cannot be controlled manually, check the fuel system. Properly cleaning the carburetor will likely fix the problem. Short-Tripping A common misdiagnosis comes from short-tripping machines engines that are started for short periods of time. Short-tripping causes the engine to develop black, sooty spark plugs and contamination in the oil. Over time, short-tripping can lead to glazed cylinder walls. To prevent this, every time the engine is started, allow the engine to reach operating temperature and load the machine.

Air Filters Note: Late model carburetors are internally vented to meet emissions standards. Engines with externally vented carburetors with a dirty air filter will exhibit rich running conditions.

When a dirty air filter restricts air flow to the carburetor, the low pressure in the venturi drops even further, resulting in a higher pressure differential between the fuel bowl and the venturi.

Note: Verify the ignition system. A rich running condition can have the same symptoms as an improperly operating ignition system. Engines with internally vented carburetors will not exhibit rich running conditions with a dirty air filter. When a dirty air filter restricts air flow to the throat of the carburetor, an equal reduction will be applied to the bowl vent. With an externally vented carburetor, a rich or lean run condition could also be caused by the location of the float bowl vent tube.

The purpose of the vent tube is to allow atmospheric pressure into and out of the float bowl. Air from the cooling fan at the vent tube opening can cause a pressure increase or decrease on the fuel in the float bowl and cause the engine to run rich or lean. Check for bulletins and relocate the float bowl vent tube to a location away from any source of turbulence. Float Valve with Worn Tip Shown Fuel level in the float bowl is regulated by the float and the float valve.

A worn float valve tip provides too much fuel and will cause a rich condition. Improper or Stale Fuel Poor fuel quality can cause an engine to appear to be running rich. Extreme corrosion may involve salt water. Sometimes the exterior of the carburetor will also be corroded. The location of the machine such as coastal regions will provide additional clues to the cause of corrosion. Red or brown corrosion is usually caused by an iron or steel part that has corroded.

Look at steel fuel inlet fittings, steel parts in fuel filters. It could also indicate some other contaminant in the fuel. Some microbial contaminations can be reddish. Brown varnish and gum deposits are generally from old degraded fuel. Look for it in areas that would be adversely affected, such as fuel and air passages, needles and seats. White corrosion or green corrosion is usually caused by water. Water can combine with other chemicals and create acids and salts which accelerate corrosion.

Water can be absorbed by ethanol, so the more ethanol, the worse the problem. Damage from excessive ethanol, methanol, MTBE, ethers, will usually be seen as damage to rubber parts. Look for cracks, swelling, shrinking, loss of elasticity, takes a permanent set or becomes hard or brittle.

Look for plastic damaged parts. Debris stuck in small orifices and other critical areas. Look in jets, fuel and air passages, fuel inlet needle and seat, idle mixture adjustment needles and seats, idle progression holes, fuel shutoff solenoid plunger, etc. Look for the following: a.

Cellulose and other organic fibers are usually grass debris that was ingested by the engine air intake or fuel system, they could also be fibers from the fuel filter element. Sand can come from ingesting dirt by the engine air intake system or fuel system or from unclean manufacturing and parts packaging.

Metallic particles such as aluminum, brass, and iron chips typically come from the manufacturing process and unclean parts packaging and assembly areas.

Do not use drill or hard wire to clean carburetor passage ways. Clean debris off the outside of the carburetor before disassembly. Completely disassemble the carburetor per the instructions in the Technical Manual and visually inspect. Plastic particles usually come from manufacturing processes such as plastic molding, welding, adhesive epoxy used in fuel filters , and unclean part packaging and assembly areas.

Determine if carburetor is repairable, excessive corrosion may determine this is not practical. Rubber particles usually come from the fuel lines, fuel pump diaphragms, or internal parts, and unclean part packaging and assembly areas. Wires and metal instruments should not be used. Light damage or deposits on the surface of the float valve seat can be removed using a cotton swab with a mild abrasive such as toothpaste or grit lapping compound.

Cardboard particles and fibers usually come from parts packaging and unclean assembly areas. Hair fibers usually come from unclean parts packaging and assembly areas.

Wrong parts, such as wrong size jet or left and right jets switched. Damaged parts, such as jets having tool marks that affect the fuel flow, cracked plastic parts, etc. Defective parts such as porosity in castings, excessive flash on castings or molded parts, defective welds or adhesive joints, throttle shafts that fit too tight or too loose, throttle plates out of alignment or not matched to bores, etc.

Carburetor Assembly When the carburetor is ready for assembly, lay out all the necessary components on a clean surface. Be aware that even clean shop rags may contain dirt and metal shavings. Assemble the carburetor in accordance with the instructions in the Technical Manual. Many times the contamination is located in an area of the carburetor that is not visible. In most cases proper cleaning can resolve these issues.

Carburetors and carburetor components can be cleaned by using one of several types of commercial cleaning methods: aerosol sprays, caustic dip tanks, and ultrasonic cleaners. Note: Some cleaning chemicals may be flammable and have toxic fumes. Always wear personal protection gear such as safety glasses.

Be sure to install the insulator using the correct orientation. This will prevent debris lodging in difficult to clean areas. Cleaning Methods Ultrasonic Cleaning Systems Ultrasonic cleaners use environmentally friendly cleaning solution and sound waves to penetrate deep into carburetor passages. Heating the solution is an option on ultrasonic cleaners that significantly increases the effectiveness of the system. Ultrasonic cleaner systems work by creating sound wave pulses that are transmitted through a cleaning solution.

Manufactures of ultrasonic cleaners claim the pulses create small bubbles that loosen and pulverizes contaminates. Select a chemical solution that is designed specifically for carburetor cleaning. Generally, chemicals will need to be diluted with water prior to use. When choosing a chemical, consider dilution rates to help determine which chemical is the most cost effective. Consider disposal of cleaning solution before ordering chemicals.

Check with local authorities on recommended disposal methods before disposing of any cleaning solution. Ultrasonic cleaners come in many sizes. Most 1. If an Ultrasonic Cleaner is used, place carburetor in and run for 30 minutes at F in the proper solution mix. If the solution is too strong or the carburetor is left in the cleaner for too long, the aluminum body will have a residue on the surface from the aluminum oxidizing.

Caustic Dip Tanks Caustic dip tanks use aggressive chemicals to dissolve carbon based contamination. This method is effective for most carburetor cleaning needs.

Rotating the parts in the tank will ensure the cleaning solution flushes out any air pockets left in the passages. Follow the recommendation on the cleaner for submersion times. Disadvantages of the caustic dip tanks are that some carburetor parts may be damaged if left in solution too long.

Personal safety and chemical disposal are additional concerns. Because the chemical is caustic, exposure may cause injury or death. Disposal of used solution can be difficult because most cleaners are considered hazardous waste. Rinse the parts in water and dry with compressed air up to 30 psi. Aerosol Cleaner Personal safety, environmental concerns and cleaning effectiveness make this method the least desirable.

This method can be used on carburetor components that may be damaged by caustic cleaners rubber seals or other. Do not use fuel or additives containing methanol as engine damage can occur. All fuel today is formulated for the automotive industry.

Newer carburetors on current production machines have less. Fuel Storage Since it is difficult to know what type of fuel is in different areas; it is best to handle and maintain fuel as outlined below: 1.

This creates deposits on engine valves and in carburetor jets and passages. This is what causes most of the performance problems. Oxygenated or blended fuels can deteriorate faster and require more specific storage and usage procedures. The translucent fuel tanks on some model tractors allow a certain amount of sunlight through the tank.

This can accelerate the deterioration of the fuel. Check Procedure: 1. Park machine safely. Remove air filter cover and air filter. Do not take internally. Avoid contact with eyes. Avoid breathing the chemical vapors. Read safety instructions on stabilizer container label before using. Fuel stabilizer contains 2,6-di-tert-butylphenol and aliphatic petroleum distillate In case of emergency, contact a physician immediately and call for material safety information.

Fill tanks with fresh, stabilized fuel. Use fuel from a major name brand supplier. At the same time, add an appropriate amount of Fuel Stabilizer such as TY Do this when you add fresh fuel to your tank. Remove the two flanged shoulder bolts B and two nuts A that hold the air cleaner base to the carburetor. If engine performance problems arise, try another brand of fuel.

You may have to try several different sources. If there is doubt about how long the fuel may be stored, add stabilizer right away.

When using this oil fuel mix, it will stay fresh for up to 30 days. If storing a 2-cycle powered unit for more than 3 weeks, it is recommended to run the fuel out of the unit. To make sure the choke is fully closed when the choke control lever is in the full choke position. Engine components are HOT.

Do not touch, exhaust pipe or muffler while making adjustments. Procedure: 1. Remove hood. Loosen cable retainer screw F. Move throttle arm E and throttle cable H to align holes in control panel and throttle control plate. Be sure bolt or drill bit is perpendicular to the control panel. Make sure throttle control lever on dash is still in FAST position. Tighten retaining screw F. Remove bolt or drill bit. Move throttle control lever through full range to be sure linkage is not binding.

Install air filter housing and air filter. Move the engine choke lever to the choke position. The carburetor choke butterfly C should be fully closed. If the choke butterfly does not completely close, loosen cable clamp D. Adjust position of choke cable to completely close choke. Move the choke control lever between the choke fully open and fully closed position several times. Ensure the choke plate fully opens and closes.

Readjust cable as needed. Air Cleaner Base Screws. To ensure the governor shaft contacts the flyweight plunger when the engine is stopped.