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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › Tell Tale signs of Improper Tuning
04-22-2011 07:16 PM  7 years agoPost 1
nickt919

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New Orleans, Louisiana

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Does it necessarily mean an engine is tuned bad, lean or rich, when the piston accumulates a dark brown discoloring at the exhaust port and/or piston top when the engine is run on 30% heli fuel/total synthetic oil?
I've had some engines run well and powerful and NOT get any brown or burnt residue on the piston ever whereas others seem to run well and I do accumulate burnt stuff on the piston top and side at the exhaust port.
I've been assuming the burnt stuff accumulated is due to a slight, or more, lean condition and getting it hot enough to cook the oil on. Is this correct? My HZ 90 and 50 both look almost as clean as the day I bought them and I consistently cook at least some stuff on my Hyper50 pistons. The brown cleans right off with solvent during a bearing change but it always seems to come on these engines.

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04-22-2011 09:47 PM  7 years agoPost 2
Santiago P

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South West, Ohio

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Residue is mostly due to the components in your fuel and operating temperature. Most fuels with all synthetic lube leave no deposits. There is some coloring due to the color die added to the fuel, some of that burns over time looking dark, but black deposites due to oil burned is a thing of the past.

Pitting and micro dents on the pistion and head surface are a sign of detonation, and brown/amber grime is usually traced to bearing rust, along with a loud gargling engine sound on idle.

Scratches on the side of the piston is the obvious indication that you found the perfect needle and...

you kept on leaning it.

Santiago

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04-23-2011 03:53 AM  7 years agoPost 3
airdodger

rrElite Veteran

Johnston USA

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LOL

Chris

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04-23-2011 07:45 PM  7 years agoPost 4
nickt919

rrVeteran

New Orleans, Louisiana

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Scratches on the side of the piston is the obvious indication that you found the perfect needle and...

you kept on leaning it.
^^ That....is good to know. Funny stuff...

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