25Series 4144 Powerhead
: Use the assembly drift (2) 
1130 893 4700 to push the piston 
pin (1) out of the piston.
If the piston pin is stuck, release it 
by tapping the end of the drift lightly 
with a hammer. 
Hold the piston steady during this 
process to ensure that no jolts are 
transmitted to the connecting rod.
: Remove the piston (1) from the 
connecting rod. 
– Inspect the piston and replace it if 
necessary
– Inspect the piston ring and 
replace if necessary, b 6.7.1
2
1
938RA064 TG
1
938RA065 TG
: Check the needle cage (1) and 
clean it if necessary
A new crankshaft must be installed 
if the needle cage is damaged, 
b 9.
– Lubricate the needle bearing 
with oil.
: Line up the piston as shown so 
that the arrow (arrow) on the 
piston crown faces the crankcase 
rib (1) and the short crankshaft 
stub (2) is on the right.
: Place the piston on the 
connecting rod.
1
938RA066 TG
1
2
938RA067 TG
: Push the assembly drift (1) 
1130 893 4700, small diameter 
first, through the piston and small 
end (needle cage).
: Fit the piston pin (2) on the 
assembly drift (1) and slide it into 
the piston.
: Remove the sleeve (1) 
5910 893 1708 from the installing 
tool (2) 5910 890 2208.
1
938RA068 TG
1
2
938RA069 TG
296RA077 TG
12