Shimming the shafts
Before assembling the crankcase halves, calculate the shims required to obtain the correct end float of the crankshaft and gearbox shafts.
Note
This engine features a single shim on crankshaft - clutch side, a single shim on gearbox primary shaft - chain side, and a single shim on gearbox secondary shaft - clutch side.
To determine the correct shim thickness proceed as follows.
Shimming the crankshaft
After fitting the new main bearings, proceed as follows to determine the thickness “SA” of the shim to be used:
-
measure the distance “LA” between the bearing contact surfaces on the crankshaft;
-
measure the depths “LA1” and “LA2” corresponding to the distance between contact surface of the crankcase halves (P) and the contact surface of the inner race of the bearings;
-
add a preload of 0.30 mm to help seat the axial load crankshaft bearings correctly. This gives: SA=LA1+LA2+0.30-LA.
Round down hundredths, if required.
Example:
if SA = 2.26 it becomes 2.25 mm.
if SA = 2.28 it becomes 2.25 mm.
if SA = 2.33 it becomes 2.30 mm.
Practical method for determining crankshaft shims
In addition to the above procedure, the following is a practical shimming method, providing a guide on how to calculate the crankshaft shim thicknesses accurately.
Install a shim (A) of minimum thickness (1.90 mm) on crankshaft clutch side to prevent contact between crankshaft crank web and engine block.
Install the crankshaft and assemble the two crankcase halves.
Fit the four M8 screws in the seats shown in the figure, and tighten them to a snug torque of 19 Nm (Min. 17 Nm - Max. 21 Nm).
Position a dial gauge (T) with magnetic stand on a support plate fixed to the crankcase.
Bring the stylus into contact with the end of the crankshaft and set the dial gauge to zero in this position.
Place a lever (U) between crankcase and crankshaft crank web pushing towards dial gauge.
Read the total clearance on the dial gauge and add a preload value (0.30 mm) plus the thickness of the shim used (1.90 mm), rounding down any millimetre hundredths.
Divide the resulting value by two to obtain the thickness of the shim packs to be installed at either end of the crankshaft.
Note
After assembling the crankcase, the crankshaft should turn with some interference in the new bearings.
 
Shimming the gearbox shafts
 
The following shims are supplied as spare parts: one per shaft.
 
Gearbox primary shaft
 
Chain side
 
1.6 mm
 
Gearbox secondary shaft
 
Clutch side
 
3.15 mm
 
Shimming the gearbox selector drum
 
The following shims are supplied as spare parts.
 
Gear control drum
 
Chain side
 
0.9 mm
 
Gear control drum
 
Clutch side
 
1.0 mm