• Itisnormalforthebearingsselectedtodifferfromonejournaltoanother.

Itisalsonormalfortheretobetwooptionsofbearingshellcolour.Insuchcases,picktheshellsizethatgivesthegreaterrunningclearance.

Note:

• Crankshaftendfloat
  Standard	0.05-0.20mm
  Servicelimit	0.40mm

  Crankshaftendfloatiscontrolled bythetolerancesincrankshaftandcrankcasemachining.Thrustwashersarenotused.Ifcrankshaftendfloatisoutsidethespecifiedlimit,thecrankshaftand/orthecrankcasesmustbereplaced.

5.14 ServiceManual-RocketIll

Pistons

Disassembly

1. Removethecylinderheadandliners(seepage

3.5).

Note:

• Theringsmayberemovedusingaproprietarypistonringexpandertoolor,ifatoolisnotavailable,carefullyspreadtheringopeningusingthumbpressurethenpushupontheoppositesideoftheringtoremoveitfromthepiston.

PistonWearCheck

1. Measure thepistonoutside diameter,1Ommupfromthebottomofthepistonandatgo^0tothe

directionofthegudgeonpin.

Note:

• Itisnotnecessarytoremovetheconnectingrodsfromthecrankshaft,butthepistonshouldbeatthetopofitsstroke.

2.Removethegudgeonpincirclipfromonesideofthepiston.

1.Gudgeonpincirclip

3.Removethegudgeonpinbypushingthepinthroughthepistonandrodtowardthesidefromwhichthecirclipwasremoved.

Note:

1. Pistonoutsidediameter

2. Measurementpoint(1OmmUpThePistonSkirt)

3. Gudgeonpin

Pistonoutsidediameteratgo0toGudgeonPin
Allcylinders	101.561-101.577mm 101.511mm

Replacethepiston1fthemeasureddiameterfallsoutside thespecifiedlimit.

• Ifthegudgeonpinisfoundtobetightinthepiston,checkthepistonforawitnessmarkcausedbythecirclip.Carefully

removethemarktoallowthepintoberemoved.

4.Withthegudgeonpinremoved, thepistoncanbedetachedfromthecon-rod.

5. Removethe pistonrings.

ServiceManual-RocketIll

5.15

PistonRings/RingGrooves

1. Checkthepistonsforunevengroovewearbyvisuallyinspectingtheringgrooves.

2. Cleanthepistonringgrooves.

3. Fitthepistonringstothepistons.Check,usingfeelergauges,forthecorrectclearancebetweentheringgroovesandtherings.Replacethepistonand ringsifoutsidethespecifiedlimit.

"'"

Aligningpistonringsusingthepiston

Checkingpistonringtogrooveclearances

3. Removethepistonandmeasurethegapbetweentheendsofthepistonringusingfeelergauges.

Pistonring/GrooveClearance
Top-standard	0.02-0.06mm
Top-servicelimit	0.16mm
Second-standard	0.02-0.06mm
Second-servicelimit	0.16mm

PistonRingGap

Note:

• Beforefinalassemblythepistonringgap,whenfittedintheliner,mustfirstbechecked.

1. Placethepistonringinsidetheliner.

2. Pushtheringintothetopofthecylinder,usingthepistontoholdtheringsquarewiththeinsideofthebore.Continuetopushtheringintotheboreuntilthethirdgrooveofthepistonislevelwiththetopofthelinerarounditsfullcircumference.

4.Ifthennggapisfoundtobetoosmall,theringendmustbecarefully fileduntilthecorrectgapisachieved.Ifthegapistoolarge,replacetheringswithanewset.Ifthegapremainstoolargewithnewringsfitted,boththepistonandlinermustbereplaced.

PistonRingEndGapTolerances
Top-standard		0.20-0.35mm
Top-servicelimit		0.55mm
Second-standard		0.30-0.50mm
Second-servicelimit		0.675mm
Oilcontrol-standard		0.20-0.70mm
Oillimit	control-service	0.875mm

PistonAssembly

1. Cleanthepistonringgroovesandfitthepistonringstothepiston.

Note:

• Thetopringuppersurfaceismarked·N'andcanbeidentifiedbyachamferontheinsideedge.

Thesecondringuppersurfaceismarked'2N'butisplainontheinsideedgeandhasabronzeappearance.

Alloilcontrolringscanbefittedwitheitherfaceupward.