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Users Manual
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You must not machine or modify the connecting rod in any way.
The needle bearings at both ends of the connecting rod are “free”
in respect to the make, but must be of the same type as the origi-
nal bearings (a needle bearing in a steel cage).
3. The cylinder and the sparkplug
The cylinder must remain totally unmodified, i.e. no machining of
any kind is allowed. For instance, deburring the edges of the cyl-
inder ports is regarded as machining and is therefore not allowed.
The sparkplug is “free”. If the thread in the cylinder for the spark-
plug should be damaged, it is accepted to repair it with a thread
set of HeliCoil type or similar.
4. The piston
It is only the original piston that you are allowed to use, with-
out any kind of machining or modification. The piston is always
marked with the name of the manufacturer (Radne), but other
markings on the crown of the piston may vary.
The markings on the piston crown are, except for the name of the
manufacturer, an A with an arrow showing which side that must
face the exhaust port. Further, on the original pistons you may find
a classification letter, where A indicates the smallest diameter and
B, C etc. indicate larger diameters.
The pistons which are sold as spare parts may not have any clas-
sification letter at all, but all spare parts pistons are class AB and
can be mounted in all cylinders.
The piston rings, the gudgeon pin and the clips are “free”, i.e. may
be changed to similar parts of another make, as long as the meas-
ures remain the same as for the original parts.
5. Standard parts
Gaskets, nuts, bolts, screws and washers are standard parts and
as such they are “free”.
6. The carburettor
The carburettor must be original Tillotson, serie HS. No modifica-
tions are allowed.
The venturi (the most narrow part of the channel through the
carburettor) must have a diameter of maximum 17,7 mm. The
diameter of the channel closest to the carburettor manifold must
be 20,5 mm.
For the class 12-15 years of age (in the Nordic countries called
class Mini), you may remove the choke shaft.
