O.S. Engines 21VZ-B V-Spec - Manual (Page 29)

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