MTD 25cc Especificaciones

Professional Shop Manual25cc 2-Cycle P25 Series EnginesNOTE: These materials are for use by trained technicians who are experienced in the service and

P25 Series of engines6Spark plugs The spark plug used in the 25cc trimmer is a Cham-pion RDJ7J (794-00055) gapped to 0.025” (0.655 mm). See Figure

Maintenance7Spark arrestor A spark arrestor is a screen that is in the outlet of the muffler. It’s job is to collect any sparks or hot embers that

P25 Series of engines8Fuel filer A dirty fuel filter can result in a lean run condition. The fuel filter should be inspected every 25 hours of use

Maintenance9StorageWhen storing a piece of gas powered equipment for longer than 4 weeks, the following procedures will prolong the engine life and mi

P25 Series of engines10For Parts Call 606-678-9623 or 606-561-4983www.mymowerparts.com

Troubleshooting11DefinitionsTroubleshooting - The act of gathering information by performing tests and direct observations.Diagnosis - A theory of wha

P25 Series of Engines12There are tools that the technician can use in order to define the problem, such as:1. Interview the customer.• Get a good desc

Troubleshooting13Identify factors that could cause the problemThis is the second step in the troubleshooting process.1. Crankshaft will not turn.• Har

P25 Series of Engines146. Starts, runs poorly• Starts, then diesI. Run the engine with a spark tester in-line between the spark plug wire and the spar

Troubleshooting15• Too much fuel: needle valve stuck or metering / emulsion issues with the carburetor.b. Blue smoke, usually light.• Too much oil in

For Parts Call 606-678-9623 or 606-561-4983www.mymowerparts.com

P25 Series of Engines16Repairing the problemThe third step in the diagnostic process is to repair the problem. This step consists of:1. Form a diagnos

Troubleshooting17Prime testTo perform a prime test:1. Prime the engine through the carburetor throat using a squirt bottle, filled with clean fresh ga

P25 Series of Engines18Compression testingTo perform a compression test:NOTE: If the engine will run, start the engine and let it warm up first for a

Ignition19Troubleshooting the Ignition SystemThe purpose of the ignition system is to provide a spark in the combustion chamber at the proper time to

P25 Series of Engines20Testing the moduleTo test the module:1. Remove the starter housing by following the proce-dures described in Chapter 6: Starter

Ignition21Test the engine stop switchTo test the engine stop switch:1. Open the grip by removing the five screws with a T-20 torx driver.2. Discon

P25 Series of Engines22ModuleRemove the ignition module:1. Remove the starter by following the procedures described in Chapter 6: starter.2. Disconnec

Ignition23FlywheelThe flywheel of an engine performs four functions:• It stores energy.• Provides the momentum that keeps the crankshaft rotating betw

P25 Series of Engines24For Parts Call 606-678-9623 or 606-561-4983www.mymowerparts.com

Fuel System And Carburetor25The function of the fuel system is to store fuel/oil mixture, mix the fuel/oil with air and deliver it to the combustion c

IChapter 1: Introduction 1Professional Shop Manual intent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Fasteners . . . . . .

P25 Series of Engines26Check the fuel/oil mixtureTo check the fuel in the carburetor:1. Get a plain piece of paper.2. Divide it into four sections and

Fuel System And Carburetor27Test fuel for alcoholFuels currently on the market contain a wide array of additives. Some of these additives oxygenate th

P25 Series of Engines28Fuel filer A dirty fuel filter can result in a lean run condition. The fuel filter should be inspected every 25 hours of us

Fuel System And Carburetor29Fuel lines• The carburetor contains a pump that draws fuel through the filter and up the fuel line. A hardened fuel line t

P25 Series of Engines30Fuel tankTo remove/replace the fuel tank:1. Drain the fuel tank.2. Disconnect the fuel lines from the carburetor. See Figu

Fuel System And Carburetor31CarburetorThe P25 series of engines uses the Walbro WT series carburetors, or a carburetor of similar design from another

P25 Series of Engines326. If the fuel/air mixture is lean:• Inspect the carburetor spacer for cracks.• Inspect the spacer O-ring.NOTE: A cracked space

Fuel System And Carburetor33Disassembly of the carburetor1. Remove the two screws that hold the primer pump body and the primer bulb to the carbur

P25 Series of Engines347. Inspect for dirt or varnish build up inside the carbu-retor. If there is a lot of dirt/varnish in the carburetor, replace it

Fuel System And Carburetor3511. Remove the throttle plate using a #2 phillips screw-driver. See Figure 5.21.12. Remove the throttle shaft E-clip. See

IIChapter 5: Fuel system and carburetor 25Fuel system troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Insp

P25 Series of Engines36NOTE: The fuel pump in the carburetor is driven by pressure pulses in the crank case. The impulse port from the spacer lets the

Fuel System And Carburetor37Re-assembly of the carburetorNOTE: The carburetor used in this manual is a Walbro. Depending on the application, the engin

P25 Series of Engines3811. Inspect the primer pump body for dirt and/or var-nish. See Figure 5.28.12. Install the diaphragm and gasket.13. Install the

Fuel System And Carburetor39Carburetor insulatorNOTE: A cracked spacer or a leaking gasket between the spacer and the cylinder could result in a lean

P25 Series of Engines406. Inspect the O-ring between the insulator block and the cylinder. See Figure 5.32.7. Install the insulator by following the p

Starters41Recoil Starter RemovalTo remove the starter assembly:1. Remove the clutch following the steps described in the section on clutch removal

P25 Series of Engines425. Remove the three screws in the front of the starter housing. See Figure 6.2.6. Slide the starter housing off of the engine.7

Starters43The starter rope, pulley and springs The 25cc P25 series of engines are equipped with the Assist Spring Technology (AST) starters.The AST sy

P25 Series of Engines44NOTE: The recoil pulley assembly consists of three parts, but it is serviced as one assembly. The three parts are: the inner pu

Starters45To assembly the starter pulley assembly:1. Install a new starter rope in the recoil pulley assembly.1a. Remove the old rope from the pul

Introduction1Professional Shop Manual intentThis Manual is intended to provide service dealers with an introduction to the mechanical aspects of the 2

P25 Series of Engines468. Secure the recoil handle to the rope using two half hitch knots. See Figure 6.11.9. Release the slip knot.10. Install the pu

Clutch and Upper Drive Shaft47Drive shaft assemblyThere are two types of drive shaft assemblies available with the P25 series of engines:• Straight sh

P25 Series of Engines483. Remove the anti-rotation screw with a T-20 driver.4. Loosen the clamping bolt with a T-20 driver. See Figure 7.3.5.

Clutch and Upper Drive Shaft49Clutch removal/replacementNOTE: The upper drive shaft may be left connected to the clutch housing. Removing the three sc

P25 Series of Engines505. Remove the clutch rotor with a clutch removal tool.NOTE: The P25 engines use a rubber clutch. Clutch tool number 797-00070 c

Engine Assembly51Theory of operation The P25 series of engines are piston ported engines. As the piston travels upward:• The exhaust port is cover

P25 Series of Engines52Engine disassemblyEconomics and parts availability will determine how much engine disassembly is feasible. There are two main l

Engine Assembly535. Rotate the flywheel so that the magnets are away from the module.6. Remove the two screws that secure the ignition mod-ule to the

P25 Series of Engines5410. Remove the two cylinder bolts using a T-30 torx driver. See Figure 8.7.11. Slide the cylinder off of the piston and connect

Engine Assembly55Engine Reassembly1. Attach the piston to the connecting rod, if removed, by inserting the piston pin.NOTE: The side of the connec

P25 Series of engines2AssemblyTorque specifications may be noted in the text that covers assembly, they may also be summarized in tables along with sp

P25 Series of Engines56NOTE: Apply a coating of Slick 50® or similar prod-uct to the connecting rod bearing as a assembly lube.5. Place the cylinder O

Engine Assembly5710. Install the flywheel and module by following the procedures described in Chapter 4: Ignition.11. Install the muffler.NOTE: Apply

P25 Series of Engines58For Parts Call 606-678-9623 or 606-561-4983www.mymowerparts.com

For Parts Call 606-678-9623 or 606-561-4983www.mymowerparts.com

MTD Products Inc - Product Training and Education DepartmentFORM NUMBER - 769-0646510/2010For Parts Call 606-678-9623 or 606-561-4983www.mymowerparts.

Introduction3Identifying enginesMTD currently has two cantilever crank, 2-cycle engines: the A31 and the P25. NOTE: The starter is mounted between the

P25 Series of engines4Model and Serial Numbers The model (item) and serial number are on a little white sticker with bar code. These are the numbe

Maintenance5MAINTENANCEThe information in this manual applies to the P25 series of engines. Some basic principles may apply to other engines produced