New member of the 'Sinker Club' (carb floats)

[Piper J3]

Cycle ignitions approx. 2 minutes after engine start with enrichener (choke) off. Do this at ~2500 RPM. Then check again at 4000 prior to flight with engine warmed up. Also check ignitions in-flight at cruise RPM. Then, when back on the ground, and engine running rough, check ignitions again at idle and at 2500 RPM. Report back findings?

[mcems]

Jim

Thanks for the reply
I cant do that its all I can do to keep it running when I can replicate it on the ground.

I little more info here. I was on a test flight yesterday and every thing was smooth and perfect. Then I notice a slight stumble didn't lose and rpms but I noticed the left EGT drop 150 degrees then recovered in seconds. So OK get back on the ground. So I tried to replicate the failure and I got it to fail again this time the right EGT dropped suddenly by 600 degrees. Flooding and shaking like **** . The fuel flow went to 10.5 GPM.

I have been doing mag checks through out all PRM ranges for the last three weeks of this search and all where perfect.

[Piper J3]

I'm re-reading your post #190... You installed new floats, or still running original floats with 1000TT?

[mcems]

i am using new floats

[NinerBikes]

Sounds like possible debris in fuel lines jamming the fuel shut off valve wide open, that the floats are trying to close down when the float bowl is full.

Check for debris in fuel tanks, lines, carbs, float bowls, to see if there are any partial obstructions.

[RFSchaller]

Brad,

Have you had your carbs overhauled?

Rich

[Piper J3]

Just spit-ball'n here... If you suspect the float is not shutting off the needle valve then perhaps remove the carbs and test on a bench. Not the easiest thing to do. You will need to make hose with banjo fitting to adapt to carb fuel inlet and then enough hose length to make column height for 5psig. It would be very tall column and not practical. So, use shorter hose and method to pressurize - perhaps a hand-bulb. Not best situation, and probably two-man operation, but it would tell you if float valve is not up to the task. You could run this experiment with float bowl on and with float bowl removed. With bowl removed, you can operate needle valve pivot by hand and observe.

[mcems]

Good Idea. Jim

Yesterday I did the the syringe testing method to see how much fuel it would take to make it run out the over flow tube. This method is explained in SB-912-065ul.

I found it only took 20 ML to overflow. So I set the flow level down and retested and got 30 ML. The Rotax SB says the correct range is 23 to 40 ML

Originally I set the float level to spec by measurement's only when I put new valve ,floats and bracket in. So my test yesterday showed the float level to high.

I will be doing some test running to see how that goes.

Thanks

[mcems]

Maybe being just a little past the acceptable level would explain the intermittent nature of the problem.

[Piper J3]

Originally Posted by mcems

Maybe being just a little past the acceptable level would explain the intermittent nature of the problem.

Yes, I believe that's possible. If, when things start to behave - do the ignition test I suggested.