40 TS 410, TS 420
– Examine and clean the mating 
surface (arrow).
The mating surface must be in 
perfect condition and without any 
damage whatsoever. Parts with 
damaged mating surfaces must be 
replaced, b 4.6.
Always use a new cylinder gasket 
after removing the cylinder.
– Position the cylinder gasket (1) 
so that the forked tab engages 
the peg (arrow).
: Fit the cylinder gasket (1).
370RA123 TG370RA124 TG
1
– Examine the intake elbow (1), 
replace if necessary. Engine 
operation may be impaired by the 
slightest damage, b 4.6.
– Remove the intake elbow (1), 
b 12.6.
: Examine and clean the mating 
surface (arrow), remove any 
remaining gasket scraps.
– Check the mating surface on the 
cylinder exhaust port and intake 
fitting.
The mating surfaces must be in 
perfect condition and without any 
damage whatsoever. A new cylinder 
must be used if the mating surfaces 
are damaged.
Screws and cover on the cylinder 
are due to production and must not 
be removed; simply loosening the 
screws can cause problems in the 
form of leaks.
370RA125 TG
1
370RA126 TG
: Place wooden assembly 
block (1) 1108 893 4800 
between piston and crankcase.
– Coat the piston, piston rings and 
inside of cylinder with oil, b 14.
– Ensure that the piston rings are 
correctly positioned, b 7.8.
– Align the tightening ring – the 
pegs (arrows) must point in the 
opposite direction to the arrow on 
the piston head.
: Slide the tightening ring (1) 
4238 893 7000 over the piston 
until it encloses the piston rings 
completely.
The tightening ring (1) must be fitted 
so that the piston rings do not 
protrude beyond the piston wall.
370RA127 TG
1
370RA128 TG
1