Flooding carburetter of nitro engine

by Tim Racine
(Centennial, CO )

When I am trying to start my plane the carburetter floods with fuel and the propeller has a hard time turning.

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Flooding carburetter of nitro engine

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Oct 28, 2009
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Tank too high?
by: Michael from Oz

G'day It would help to know a bit about your engine and how it is set up but a couple of general principles may help.

1. The carby should always be set up so that it is about the same height as the centre line of the engine - ie if the tank is half full, the carby would be at the same level as the fuel

2. Most engines will start with the high speed needle about 2 to 3 turns open. This will give a rich setting and you can then turn the needle in to get a running setting (just rich of peak revs).

If your carby is considerably lower than the tank, fuel will siphon out and just keep running out of the carby and may flood the engine particularly if it is a two stroke which is mounted cylinder up. Fuel will drain into the engine and try to fill the crank case, then when you try to turn it over, a large amount of fuel will be forced up the transfer ports on to the piston and if there is too much liquid, you can damage the engine with your starter or even if you flick it hard.

The solution is to have the tank at the right height.

If it is totally impossible to lower the tank, then you can use a CLINE fuel regulator or you can clamp the fuel line to stop the flooding. Then you have to prime the engine with a small amount of fuel with the line clamped, start the engine on the prime and release the clamp as the engine starts. This is less than ideal.

It is quite easy to wreck and engine that is flooded with an electric starter. Usually either the conrod will fail or in extreme cases, the crank shaft may be damaged.

Does this help at all?

Mike from Oz

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Oct 28, 2009
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Submitted by: Michael from Oz

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G'day It would help to know a bit about your engine and how it is set up but a couple of general principles may help. 1. The carby should always be set up so that it is about the same height as the centre line of the engine - ie if the tank is half full, the carby would be at the same level as the fuel 2. Most engines will start with the high speed needle about 2 to 3 turns open. This will give a rich setting and you can then turn the needle in to get a running setting (just rich of peak revs). If your carby is considerably lower than the tank, fuel will siphon out and just keep running out of the carby and may flood the engine particularly if it is a two stroke which is mounted cylinder up. Fuel will drain into the engine and try to fill the crank case, then when you try to turn it over, a large amount of fuel will be forced up the transfer ports on to the piston and if there is too much liquid, you can damage the engine with your starter or even if you flick it hard. The solution is to have the tank at the right height. If it is totally impossible to lower the tank, then you can use a CLINE fuel regulator or you can clamp the fuel line to stop the flooding. Then you have to prime the engine with a small amount of fuel with the line clamped, start the engine on the prime and release the clamp as the engine starts. This is less than ideal. It is quite easy to wreck and engine that is flooded with an electric starter. Usually either the conrod will fail or in extreme cases, the crank shaft may be damaged. Does this help at all? Mike from Oz

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