Husqvarna 343F, 345FX, 345FXT, 343R, 345RX manual Cylinder and piston, Dismantling

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6	Cylinder and piston

The cylinder and the piston are two of the compo- nents exposed to most strain in the engine. They must withstand, for example, high speeds, large tempera- ture swings and high pressure. Moreover, they must be resistant to wear. Despite these tough working conditions, major piston and cylinder failure is rela- tively uncommon. The reasons for this include new coatings in the cylinder bore, new types of oil and grease and refined manufacturing techniques.

When servicing these components, cleanliness is of the utmost importance. It is therefore recommended that the cylinder and the area around it be thoroughly cleaned before being dismantled from the crankcase.

A

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Dismantling

Dismantle the following components to make the cylinder accessible:

Starter, cylinder cover, muffler guard, muffler and spark plug.

NOTE!

The throttle need not be removed to dismantle the cylinder and piston.

Loosen the clamp (A) and unscrew the bolt a good distance (to facilitate the coming assembly) so that the clamp can be turned around the inlet manifold without affecting the cylinder.

Then loosen the 4 bolts holding the cylinder.

Carefully lift out the cylinder by twisting is backwards and forwards until it loosens from the inlet manifold. Make sure that no dirt enters the crankcase.

Use a rag to cover the crankcase opening under the piston.

502 50 18-01

Remove the circlips from the gudgeon	Using long-nose pliers remove the
pin.	gudgeon pin circlips.

Keep your thumb over the circlip to prevent it from flying out.

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Contents English Workshop Manual Brushcutter, Trimmer Model 343R, 345RX, 343F, 345FX, 345FXT ContentsGeneral recommendations Starter ContentsDismantling 1StarterStarter AssemblyReplacing the drive dogs Electrical system Checking the ignition spark Electrical system502 71 Tip 502 50 Replacing the spark Plug cover502 54 Heated handles Drive dogsWiring diagram Electrical system Fuel system Air filter Fuel systemFuel filter Tank ventingCarburettor Fuel pumpDismantling Metering unit Carburettor’s designBlending unit Dismantling the carburettor Pump unitFuel system For example, the H-needle is a PositionedLittle shorter than the L-needle Assembling the carburettor Are not bent or pinched when H-needle is a little shorterThan the L-needle Check carefully that the fuel hosesBasic setting Carburettor settingsFine adjustment Idling speed T-screw Setting Recommended max. speed must not be exceededCorrectly adjusted carburettor Tachometer should always be used to find the optimalRotating Carburettor adjustment 345RX/FXAdjusting the L-needle Adjusting the H-needle ThrottleCheck for wear on pins a and B Tip Page Centrifugal clutch 502 21 Centrifugal clutchDo not lose the sleeve bearings found in the clutch shoes Centrifugal clutch502 11 Clutch drumChange the bearings in the clutch housing if necessary Page Angle gear Let the small circlip around the axle remain Angle gearInput axle with pinion must be dismantled first 503 97503 80 ShaftCylinder and piston Cylinder and piston When the valve is fitted the small hole must face outwards Turn the valve the right way when fittingDecompression valve Inlet manifold Cleaning, inspectionInsufficient lubrication Analysis and actionsCause Action Piston scoring caused by heavy carbon deposits Piston ring breakage Piston damage caused by a too high engine speedCause Foreign objectsDefect Action Service tipsWear tolerances Crankshaft and crankcase Crankshaft and crankcase 502 52 Crankshaft and crankcaseInspecting Crankshaft Assembly To ensure a proper seal Leakage testing CrankcasePress down the sealing plates as Far as possible between the bolts503 55 Husqvarna E-Tech