Vortex ROK DVS JUNIOR, Owner'S Manual

Page: 16 / 39

4.12. Piston
Oils produce carbon deposits or
residues that make necessary the spark
plug to be checked and cleaned, at
least every race.
Be aware, cylinder head volume may
be changed after the race, carbon
deposits may cause variations on the
cylinder head volume.
Every 30 hours piston must be
replaced.
In order to perform this job, we highly recommend
taking the engine off the chassis. However, you may do
the job even with the engine mounted.
1. Take away the muffler from the engine by removing
the 2 springs fixing it to the exhaust manifold.
2. Unscrew and remove the spark plug (16).
3. Unscrew and remove the 6 nuts on top of head (19)
and the 6 washers (20).
4. Remove the head by pulling it up carefully.
5. Unscrew the 4 nuts on top of head.
6. Remove the cylinder with one hand by pulling it up. To
avoid contact with the crankcase, use the other hand to
hold the connecting rod.
Whenever you disassemble the cylinder, we
recommend replacing the cylinder gasket (27).
6. Remove the 2 piston pin circlips (32) by squeezing the
ends together with the needle-nose.
7. Hook the connecting rod each side with two fingers.
8. Push the piston pin (33) off the piston by using a
proper tool.
9. In order to avoid damages pull the piston up with one
hand while holding the connecting rod with the other.
10. Take the roller bearing off the connecting rod.
ASSEMBLING
Check the tolerance between piston and cylinder.
Wrong tolerance may cause serious damage.
11.
Lubricate and replace a new roller bearing, if needed,
on the connecting rod.
12. Insert a new piston in the connecting rod. The arrow
marked on top of it, must face the exhaust port.
13. Insert the piston pin into the piston.
14. Insert piston pin circlips on each side of the piston.
Be aware, wrong assembly of piston pin circlips may
cause important damage.
15.
Fit the piston ring and check both ends close properly
against the brass pin inserted in the piston.
16. Place a new gasket (27) into the 4 studbolts.
17. Insert the cylinder into the 4 studbolts carefully and
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