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fuel coming out of vent tubes

  • Roy Evans
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2 weeks 4 days ago #18153 by Roy Evans
Roy Evans created the topic: fuel coming out of vent tubes
hello, i have a Rotax 912 ul 80 hp it has two 64 carbs on it and they were rebuilt but fuel is comming out of both vent tubes on the cabs the floats are set corectly at 10.5mm from the base of carb. they have all new parts...help please

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2 weeks 4 days ago #18155 by RotaxOwner Admin
RotaxOwner Admin replied the topic: fuel coming out of vent tubes

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2 weeks 4 days ago #18156 by Roy Evans
Roy Evans replied the topic: fuel coming out of vent tubes
i have.. the fuel is coming out constanty out of both vent tubes while on the ground with the 3 inch tubes

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  • Rodrigo Echenique
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2 weeks 4 days ago - 2 weeks 4 days ago #18157 by Rodrigo Echenique
Rodrigo Echenique replied the topic: fuel coming out of vent tubes
Hi Roy,
Check that both carburators are perfectly vertical, if they are installed in an angle this can cause the neddle float to stuck and you will have a leak at the vents, if the carburators are perfectly vertical and you have a leak at the vent of both carburators you will need to disassemble them again and first check the flotability of each float then check that you don´t have any debris in the float neddle seat and check also the the tip the the float neddles are not damaged.
I s very strange that both carbs have a float neddle leak and more when they where rebuilt, for sure they are not well assembled.
If you did the work check it again and before closing the carburator bottom cup, check thta when you push the floats you have a perfect seal of the needle.

Also check the height of the floats when they push and close the neddle that supply the fuel

Regards
Last Edit: 2 weeks 4 days ago by Rodrigo Echenique.
The following user(s) said Thank You: Roy Evans

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2 weeks 4 days ago #18161 by Roy Evans
Roy Evans replied the topic: fuel coming out of vent tubes
All have been rechecked by myself irmt-A and another a&p irmt again restarted and again fuel coming out of vent tubes... Is possible that the fuel pump is putting out more than 7.5 p.s.i. causing this problem?????

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1 week 1 hour ago #18263 by Rodrigo Echenique
Rodrigo Echenique replied the topic: fuel coming out of vent tubes
I don´t think so, check the flotability of your floats
Your fuel pump will give you about 5.5 psi and with this pressure and even with about 8 psi a good pair of floats and the needle valve will not open and this pressure.
Are you sure you installed the seat of the needle valves or your teied to clean the seats that maybe you damaged the seats of your needle valves of the floats?
Here I have some carbs, I will make a test at how much pressure they will open

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6 days 10 hours ago #18273 by Rob Seaton
Rob Seaton replied the topic: fuel coming out of vent tubes
What type of aircraft? are the carbs and manifolds swapped to the outboard position like a Kitfox 4?
maybe the carbs are shaking too much?
Are the pneumatically carbs synced at idle?
Idle too low?
Engine mount weak (not containing torsional vibration)?

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