Piston engine problem Brisbane - SEIZED
PISTON ENGINE PROBLEM: COMPLETE FULL SKIRT PISTON SEIZURE.
If the engine has had a serious overheat the abnormal expansion of pistons and rings in the bore will
cause excessive friction and again a breakdown of lubrication will eventually result in an exchange
of molten material from the pistons to the bore and visa versa
"Seized pistons" in an engine that has had no serious overheating problems is usually caused by
a breakdown of lubrication. This can be the final result of rings fitted with insufficient ring back
clearance or ring end gap. If the engine is driven long enough after symptoms start to develop (lack
of power, pinging, etc) the result will eventually be piston seizure. As the friction increases the
lubrication breaks down and a complete piston seizure will result in a very short time. As this
happens the piston will be permanently seized in the bore. Items to eliminate as the cause include:
insufficient ring back clearance, no or insufficient ring end clearance, poor lubrication, failed cooling
system, insufficient piston to bore minimum clearance, severe loading conditions and severe tuning
problems. ( retarded, over- advanced, lean mixture.) "Complete skirt seizure" is usually a result of
driver fault. What happens commonly is that an engine suffers from any of the above causes and the
driver feels a loss of power from the engine but continues to add more throttle as the vehicle slows
down. This extended and increased load takes the already minor piston pick up to the next level of
complete seizure. This is where the piston and bore transfer material across to each component
until complete seizure stops the engine running. Often severe damage occurs to other components
and the heat generated can even transfer through the block and melt even external components like
coils, leads, carburettors and any plastic component bolted to the engine.
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UMR Engines
Centre skirt scuffing
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