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ENGINES Bolen
BOLENSCO NDENSED SERVICE DATA
Year MadeENGINE MODEL....Bore(mm)
InchesStroke(mm)Inches
No. ofCylindersDisplacement (cc) . . . .Cubic Inches
Horsepower (o RPM ..Cooling TypeCarburetor Model . . . .
Number UsedIgnitionTypePoint Gap (mm) . . . .Inch
Timing Advance? . . . .Timing BTDC (mm) ..InchMeasured At
Sprak Plug:BoschKLGChampionElectrode Gap (mm)Inch . .
Fuel/Oil Ratio
1970 1971
T2-2Z15602.362552.165231018.9
2Z15.70602.362552.165231018.9
HL279A2 HL279A1
19712Z300
582.283552.165229117.8
CentrifugalHR89A1
19712Z340
622.441552.165233220.324(6000FanHR89A
1
19713Z400
552.165552.165339324.028@6000
HR89A1
19713Z440
582.283552.165343226.432(0)600
HR89A1
-BOSCH Energy Transfer Magneto-0.35-0.450.014-0.018No2.2
0.087W260T1FFIOOL5
0.60.02420:1
No2.20.087
W260T1FFIOOL5
0.60.02420:1
Yes2.350.093Advance
W260T1FFIOOL50.60.02420:1
Yes2.250.093Advance
W260T1FFIOOL5
0.60.02420:1
No2.20.087
W260T1FFIOOL5
0.60.02420:1
No2.20.087
W260T1FFIOOL50.6
0.02420:1
C A R B U R E T O R A D J U S T M E N T
Fig. 1-On SPRINT, TW-315, anAdjustmentPlate isattached tocarburetor baffle. Check tosee that plate Is inplace and that main jet forNo . 2 carburetor is V4-turnrichas shown.
CO\i .Fig. 2-Breaker plate with flywheel removed.Wires leading toignition coils areidentical andcontinuity should bechecked tomake sure
MAINTENANCECARBURETOR. On 1970 model
TW-315, twin carburetors are used.Adjustment instructions are carried onan instruction plate attached to car-buretor deflector as shown in Fig. 1.Recommended adjustment specifiesthat high speed jet for left hand cyl-inder be V4 turn farther open than right
hand setting. Normal adjustmrange is l-V . turns open from cposition for right hand (No. 1) buretor. Refer to appropriate buretor paragraphs in FUNDAMTALS Section for additiadjustment and overhaul informat
IGNITION AND TIMING. Brepoints for No. 1 (flywheel end) cyli
3-EKploded view of2Z15 engine.1 . Oil seal2 . Front crankcase3 . Bearing4 . Shim5. Pin bearing6. Front crankshaft7. Pi8ton pin8. Piston9. Piston rings1 0 . Gasket1 1 . Dowel1 2 . Crankshaft lock screw1 3 . Pulse fitting1 4 . Center crankcase1 5. Rear crankshaft16 . Rearcrankcase1 7 . Rear bearings1 8. Snap ring1 9 . Oil seal2 0 . Snap ring2 1 . Gasket2 2 . Cylinder2 3 . Gasket2 4 . Cylinder head2 5 . Special nut2 6 . Sparkplug2 7 . Gasket2 8 . Exhaust pipe
6 4 3
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points to recommended gap, th ening for No, 1 cylinder using a
o. 1 p is ton p roper ly t im ed, m ove
alike as possible.LUBRICATION. The engine is lu-
are recommended.Mix fuel and oil thoroughly using a
sene or fuel oil for prem ixing .REPAIRSTIGHTENING TORQ UES. Recom-
head nu ts 20nuts 10shaft clamp screw 30nut 80
screw (1 2~Flg. 3) clamps crank'countersunk hole indicated by arrows.
D I S A S S E M B L Y A N D R E A S -SEMBLY. Refer to Fig. 3 for explodedview of engine. When service is re-quired, first remove engine, then re-move carburetors, cooling shrouds, ig-nition block, recoil starter, flywheeland magneto.Remove cylinder heads. Heads areinterchangeable, but No. 1 (magnetoside) head is installed with fins run-ning parallel with crankshaft whileNo . 2 (output side) head is installedwith cooling fins crosswise.Remove cylinders, piston pins adpistons. Pins are full floating and canusually be pushed out after removingretaining rings. Heat pistons slightlyusing mild heat, if necessary. Crank-shaft units are keyed together and re-tained by a clamp screw (12) and splitcounterweight. Refer to Fig. 4. Loosenthe screw and remove nuts from crank-case through-studs; then tap on crank-shaft (Fig. 5) to separate the doweledhousings.The five crankshaft bearings are atight press fit in housings at roomtemperature but can be easily removedafter heating housings with an electricheat gun or other form of mild heat. Ifbearings are renewed, measure depthof each housing half (Fig. 6); add thetwo measurements and subtract thedistance between crankshaft shoulders(Fig. 7); then add shims (4Fig. 3) asnec essa ry so end clearan ce in eachcrankshaft half is 0.008-0.012 (inch),measured without gasket (10). Shims(4) are av ailable in thickne sses of 0.1,0.2 and 0.3 mm (0.004, 0.008 and 0.012in.).
Fig. 6-Measuring crankcase depth to deter-mine thickness of crankshaft shims.
5-Use soft drift and hammer to
ENGINESArrow on piston crown must be in-stalled toward exhaust port side of cyl-inder block. Refer to the appropriatefol lowing paragraphs for inspect ionand overhaul notes.PISTON RINGS AND CYL-INDER. Cast iron cylinder can be re-bored, and pistons and rings are avail-able in oversizes of 0.010 and 0.020 as
wel l as s tandard . Arrow on top ofpiston crown must be installed towardexhaust port.Cylinder head is symmetrical andinterchangeable. Cooling fins must beinstalled as shown in Fig. 8 on twocylinder models and as shown in Fig. 9on thre e cylinder engines.CRANKS HAF T AND CON-NECTING ROD. The crankshaft andconnecting rod for one cylinder is onlyavailable as an assembled unit. Wearof parts at rod big end can be tested byrocking small end of rod. Play shouldnot exceed 1/16 inch.
Fig. 8-On BOLENS Twins, No. 2 cylinder headis instaiied with fins crosswise as shown. Referaisq to cyiinder heads in Fig. 3.
IIi fOllllrttO11
l l l loIIIIoH
IMtttHIBo
IIIBomoI l l l l Jand Fig. 7-Measuring crankshaft length to deter- Fig. 9-On Three Cylinder Engines , cylinder
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