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fuel coming out of vent tubes

  • Privatepilot
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6 months 2 weeks ago #18153 by Privatepilot
fuel coming out of vent tubes was created by Privatepilot
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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6 months 2 weeks ago #18155 by admin

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6 months 2 weeks ago #18156 by Privatepilot
Replied by Privatepilot on 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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6 months 2 weeks ago - 6 months 2 weeks ago #18157 by Rodeche
Replied by Rodeche on 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: 6 months 2 weeks ago by Rodeche.
The following user(s) said Thank You: Privatepilot

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6 months 2 weeks ago #18161 by Privatepilot
Replied by Privatepilot on 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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6 months 3 days ago #18263 by Rodeche
Replied by Rodeche on 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 months 2 days ago #18273 by RobSeaton
Replied by RobSeaton on 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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