Overhaul of the connecting rods
Remove the engine from the frame (Removing the engine).
Remove the timing outer covers (Removing the timing outer covers).
Remove the timing belts (Removing the tensioner pulley/timing belt).
Remove the timing belt pulleys (Disassembling the camshaft pulleys).
Remove the complete cylinder head unit (Removing the engine heads).
Remove the cylinder/piston assembly (Removing the cylinder/piston assembly).
Remove the generator side cover (Removing the generator cover) and the complete generator (Removing the flywheel/generator unit).
Remove the starter motor (Removing the starter motor).
Remove the clutch cover (Removing the clutch cover).
Remove the clutch unit (Removing the clutch).
Remove the oil pump (Removing the oil pump).
Remove the primary drive gear (Removing the primary drive gear).
Remove the mesh filter (Changing engine oil and filter cartridge).
Separate the crankcase halves (Separating the crankcase halves).
Remove the connecting rod assembly from the crankcase halves (Removal of the connecting rod assembly).
Disassemble the connecting rod assembly (Disassembly of the connecting rod assembly).
Make the following dimensional checks on the connecting rods:
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clearance with gudgeon pin on assembly.
In the event of excessive wear, replace the connecting rod. The small end bushing must be in good condition and firmly driven into its seat. Check for parallelism error measured at 100 mm from the connecting rod longitudinal axis:
it must be H-h lower than 0.02 mm (standard H of the new part is 124 mm); otherwise replace the connecting rod.
Big end diameter must be within the specified range.
It is preferable to use crankshafts and connecting rods of the same size class.
Renewal of the connecting rod bearings
It is good practice to renew the bearings (4) each time the engine is overhauled.
Replacement bearings are supplied ready for assembly and they must not be reworked with scrapers or emery cloth.
The bearings may belong to two different size classes, each identified by a specific colour (S) (RED and BLUE).
The bearings are comprised of an external steel ring, the inner face of which is electro-plated with a lead-based compound.
The table shows the appropriate bearings to be fitted according to the size class of the crankshaft.
 
Crankshaft class
 
Con-rod class
 
Bearings colour
 
A
 
A
 
RED - RED
 
B
 
A
 
BLUE – BLUE
Crankshaft overhaul
The main bearing and big-end journals should not be scored or grooved.
The threads, keyways, and slots must be in good condition.
Check for fretting or burrs in the fillet between journal and shoulder.
Fillet radius: 1.5 mm.
Use a micrometer to measure oval and taper of the crank pin. Measure oval and taper in several different directions.
Use a dial gauge to measure the alignment of the main journals by setting the crankshaft between two opposing centres.
Use a hot air gun that can reach 150 °C.
Loosen crankshaft plug (5), heating the crankshaft, if necessary, to remove the sealant applied upon assembly.
Clean all the oilways using suitable diameter metal brushes and then blow with compressed air to remove any residues that have accumulated and are restricting the oil flow.
Apply recommended threadlocker on the grub screw threads (5) and (6) and reinstall them.
Tighten grub screws to a torque of 13 Nm (Min. 11 Nm - Max. 15 Nm).
Big-end bearing-crank pin clearance
To pair the big-end bearings - crank pin, it is necessary to proceed as follows:
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smear a bead (A) of “Plastigauge PG-1 GREEN” on the crank pin;
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fit the original con-rod and big-end bearings.
Tightening procedure
Tighten the connecting rod screws (Class 14.9) as described below:
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apply specified threadlocker on the thread;
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tighten the screw to a torque of 35 Nm ± 10% at 50 rpm;
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after a 2-second pause, loosen by 360° at 30 rpm;
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tighten to a snug torque of 20 Nm ± 10% at 30 rpm;
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tighten to a snug torque of 35 Nm ± 10% at 10 rpm;
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tighten by turning 65° ± 1° at 14 rpm;
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Check the applied tightening torque (Min. 70 Nm - Max. 113 Nm).
Continue the pairing procedure as follows:
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loosen the screws and remove the con-rod;
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check the thickness of “Plastigauge PG-1 GREEN” (A), using the special reference tool (B);
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the thickness measured with tool (B) is the actual clearance: if the clearance is not within the specified limits (Crankshaft), it is necessary to replace bearing shells or the crankshaft and repeat the procedure;
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If the clearance value is within the specified limits, thoroughly clean the crankshaft from “Plastigauge PG-1 GREEN” (A) and repeat the described tightening procedure.