25MS 440, MS 440 C
: Examine the reflector foil (arrow) 
and replace it if necessary – 
b 6.7.2
VA
176RA061
: Fit the heat shield (1) in position.
: Position a new gasket (2) with the 
bead (3) facing outwards.
– Coat the screw threads with 
Loctite – b 16. 
VA
176RA008
2
1
3
– Tighten down the screws – b 3.5
When assembling the parts, ensure 
that size M6x20 screws are fitted at 
the bottom and size M5x6 screws at 
the top to secure the exhaust 
casing.
Versions with catalytic converter 
only
: Fit M6x30 screws (arrows) with 
tensioning gear.
: Insert M5x30 screw (1) with 
sleeve.
VA
176RA323
1
Defective oil seals and gaskets or 
cracks in castings are the usual 
causes of leaks. Such faults allow 
supplementary air to enter the 
engine and upset the fuel-air 
mixture.
This makes adjustment of the 
prescribed idle speed difficult, if not 
impossible.
Moreover, the transition from idle 
speed to part or full throttle is not 
smooth.
The crankcase can be checked 
thoroughly for leaks with the 
carburetor and crankcase tester 
and the vacuum pump.
6.2 Leakage Test