Carb flooding and venting, Kitfox4 912 UL

[Bob]

After a 5 year rubber replacement, we started the engine to check for leaks and balance the carbs. In the course of the replacement, we had removed a fuel regulator which the previous owner had in the line to the carbs from the fuel pump. Checking with Lockwood Aviation, we had been told that was non standard and not needed to regulate fuel pressure. After starting, the engine ran well for several minutes. Then both carbs began venting and flooding. I consulted the previous owner as to why the fuel regulator was installed. His response was the the carbs had begun to vent and flood. So, he had installed the regulator to reduce the fuel pressure and stop the flooding and venting. The solution I have in mind is to replace the both carbs.

I am wondering if anyone has encountered a similar situation, or would like to comment. Thanks.
Bob

[jiott]

Before replacing the carbs, I would suggest you replace the little rubber-tipped needles AND the seats in both carbs. Very likely they are worn and don't seal well at the normal fuel pressure.

[Bob]

I bought the 5 year Hose and Rubber Component list from Lockwood Aviation which included the fuel pump, float needles, diaphragm, Carburetor Overhaul Kit, etc. I think the seat might be at fault. Lockwood thought so too, with no guarantee that they could fix it. Rather than loose more time, I'm going to bite the bullet with new carbs. Toys that don't work are kind of useless. Thanks for your comment.
Bob

[rv9ralph]

Did you check the floats to ensure they do not sink. Rotax-Owner.com has the Service Bulletin detailing the process.

Sinking floats will not close the needle valve that keeps the fuel bowl from overfilling and spewing fuel out the vent lines.

Ralph

[desertdave]

That's what happened to mine. I pulled the carb bowls off and one of the four floats was sitting at the bottom of the bowl. Sounds like Bob wants to get back flying ASAP with ordering new carbs.

[Av8r3400]

Did they supply the red or black needles? I believe the red ones are softer and work better with the reversed intake manifolds on a Kitfox 4.

[avidflyer]

If you want a deal on new carbs, Jason Busat from BadAss powersports sells new carbs with intake manifolds and fuel pump for $1250. I got a set from him and they are new. He strips these parts off new engines and puts fuel injection on the engines. Here is the stuff I got from him a couple of months ago. JImChuk

PS a pair of floats should not weigh more then 7 grams together. I've seen them weigh as low as 2.8 grams each. I would verify this is not the problem. Also, do you have a return line? New style fuel pumps make more pressure than old style ones.

[Bob]

Did you check the floats to ensure they do not sink. Rotax-Owner.com has the Service Bulletin detailing the process.

Sinking floats will not close the needle valve that keeps the fuel bowl from overfilling and spewing fuel out the vent lines.

Ralph

The floats floated. Thanks for the comment.
Bob

[Bob]

If you want a deal on new carbs, Jason Busat from BadAss powersports sells new carbs with intake manifolds and fuel pump for $1250. I got a set from him and they are new. He strips these parts off new engines and puts fuel injection on the engines. Here is the stuff I got from him a couple of months ago. JImChuk

PS a pair of floats should not weigh more then 7 grams together. I've seen them weigh as low as 2.8 grams each. I would verify this is not the problem. Also, do you have a return line? New style fuel pumps make more pressure than old style ones.

The weight of the floats checked in at 2.8g each. The new pump has three accesses IN, OUT, and VENT. The stuff looks very nice. The new carbs were $ 1100 something. Thanks for the reply.

[Bob]

Did they supply the red or black needles? I believe the red ones are softer and work better with the reversed intake manifolds on a Kitfox 4.

The new needles were black.

Thanks.