O.S. Engines 18TM Revo - Manual (Page 29)

Unsuitable glowplug
Unstable idle
Use suggested glowplug in the instructions.
Unsuitable fuel
Extremely light flywheel
Do not use extremely high nitro or low oil fuel.
Add suitable load.
Install silencer securely. Silencer is disconnected or has play
Replace the tubing.
Replace seal ring.
Check the connections and secure them.
insufficient warming up or running-in.
Fuel tubing from tank to is split or broken.
Silencer or manifold is not securely connected
or disconnected.
Set the needle only after warming up.
Complete running-in.
Not reaching expected peak r.p.m.
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