912 flooded carb

[taco]

Would like some advice. My right carb continued to flood out through the air tube with mechanical fuel pump at about 4#s. Put a pressure regulator on the gas line with a setting of 2#of pressure and bypassing the electric fuel pump. The pressure gauge when running shows 2.5 # and the flooding stops. The engine runs smooth at various rpms with run-up to 5000psi. Everything seems good. Question - is 2.5 lbs. of gas line pressure adequate for flight? If so, i will replumb through the electric fuel pump which i only use for takeoff and landing. Would appreciate your thoughts! thanks.

[Delta Whisky]

Taco - have you done anything to uncover the real source of the flooding? (Or, why isn't the float and valve doing its thing - properly?)

Past that though, is 2.5lbs enough? That question is best answered by a fuel flow test. Can you run your system the way it is plumbed by the electric pump with the pressure regulator set to 2.5#s? With a pump system you need 125% of rated max power fuel flow. I forget the exact numbers for a ULS but it should turn out to be almost 10 gph.

[Av8r3400]

I would consider at least replacing the needle valves, if not the floats, too. IMO 2.5 psi is not enough fuel pressure.

[109JB]

Well that all depends. There are many gravity feed systems that operate on less than 1 psi. Motorcycles, ATVs, lawn mowers, and airplanes come to mind. However, it depends on the carburetor and how it is designed to function. The Rotax 912 manual I have list fuel pressure limits from 2.2 to 5.8 psi, so 2.5 is in the green but at the low end. That said, 4 psi should not cause the carbs to overflow and there is something wrong. The carb floats on rotaxes are a know problem, and there is a test for weight of the float to determine if it is fuel soaked. Coincidentally the 582 uses the same floats as a 912 and I had a bad float on my 582 that caused the same issue. Replaced the float and all is good. Bottom line is you really need to find out what the real problem is, and 4 psi of fuel pressure is not the problem.

[taco]

Thanks for your thoughts! I think your right, there is a problem and regulating the psi to 2.5 really doesn't solve it. the floats are good so plan on mechanical sync to see if that helps and go from there. don't really want to take carb off but may have to replace needle. not mechanically inclined so all this is difficult. thanks.

[Av8r3400]

What was the weight on the floats?

Needles can be done with the carbs in place.

Maybe you might consider having the carbs professionally gone through.

[ScottS97385]

Thanks for your thoughts! I think your right, there is a problem and regulating the psi to 2.5 really doesn't solve it. the floats are good so plan on mechanical sync to see if that helps and go from there. don't really want to take carb off but may have to replace needle. not mechanically inclined so all this is difficult. thanks.

Did you weigh the floats?

You can get one of these from Amazon for under $10.00

30582

[Slyfox]

this kid has the same problem, right carb, left is ok. Now my plane is a 4 so the original left carb is now on the right. went 800 hrs with no problem, now the right one wants to flood and only when it's hot. I let things cool and turn on the facet pump and no leak. I fly for a half hour and taxi back to hangar and rough. stop and fuel is pouring out the vent of the right carb. I've rebuilt the carbs, replaced the floats (new), replaced the arm, replaced the needle, polished the seat. replaced the bowl with the updated one. I don't know what to do next other than replace the carb. Larry you say the needles with the red tip, you got a part number.

[taco]

yes, i weighed the floats and under 7oz. I've read it's really difficult to replace needle valves with the carb in place, is there a simple way to do it? first i am going to resynch the carbs both mechanically and pneumatic. dont know if vibration problem causing overflow? thanks.

[Slyfox]

Taco, first off mine would leak with engine off. Now I replaced my original needle and arm because I would get a little fuel on the floor about the size of my hand when I came into the hangar with the fuel on. So a long while back I started turning the fuel off after flight. I changed out the needle and arm and started having flooding problems. Now with that said the definition for NEW is = never ever worked. So I just went out to the hangar and put the old needle and arm back in, I run the facet pump and flushed the needle real good and made sure it was centered good. I put things back together and ran it, ran great, and warmed it up good. no leak so far. I put things back together and am now waiting for good weather, high winds right now and thunder storms coming through. will see how things work out.

[Slyfox]

I took and loosened the carb and rotated it on a 45 and pushed the pin out with a small punch, hit it with a wrench to loosen it. the pin has perforations on one side, you need to look for that and hit on the other side. mine was on the inside so I hit on the outer side of the carb (right side) and slowly removed the pin. hope this helps.

[Av8r3400]

this kid has the same problem, right carb, left is ok. Now my plane is a 4 so the original left carb is now on the right. went 800 hrs with no problem, now the right one wants to flood and only when it's hot...


I was trying to find them on the LEAF website, without luck. Maybe give them a call, ask for Brett and see if he knows if they still make the softer tip needles. They used to have red or black tips. I think the red ones were the softer ones. I still have the original 1996 tips (and floats) in my carbs because the new ones sucked so bad.

[Slyfox]

I put my original needle back in and flew it again and no flooding, time will tell I guess. thanks larry

[Slyfox]

I put on some new carb sockets last night (jbm) mine were very old(jbm) and found a nice improvement. I flew this morning and it was nice and smooth full throttle, just a little rough not bad in the lower rpm's. No more flooding, the new needle I got must be junk. I'm just going to fly it, when I have time I might take the mid range jet out and soak it in gun cleaning solvent. I need to do that with my injectors for the rv, I do that when I change the oil. The kitfox is time for an oil change so that will be the time I do that one. take care see you a OSH.

[AvDES LLC]

Next time you open up the carbs you may want to polish the needle seat as well. I had these same issues and leaks with the new replacement needles as well. Upon taking an eye loop and staring into the needle seat, you can see chattering from the drilling process that resulted in the needles not being able to completely seat and thus fuel leaked by. I took some metal polish, a q-tip (or 3) and a drill to solve that issue.

pull the cotton tips off of 2 or 3 q tips and wrap them around the head of another q-tip. Just building up the cotton to ensure that it polishes all surfaces in the seat simultaneously. Then a dab of metal polish and chuck the ass end of that q-tip into the drill and give it a go. I DO NOT suggest spinning that drill at super high speeds - be smart and realize polish is an abrasive and too much pressure will chew up some serious material. Polish slow and blast out residual with carb cleaner. Turn in fuel briefly after completion to ensure no polish snuck up through the port and into the fuel line. Once it runs clean, re-sssemble, verify fuel level in bowl, grab a handful of gummy bears and pat yourself on the back for a job well done.