The Cessna 120-140 Association Forum

Still trying to master my take off and landings!! Flew with my tailwheel instructor yesterday. Weather was low humidity cool around 45F. Run-up was normal. Adding takeoff power engine stumbled between 1500 rpm and 2000 rpm, then smoothed out and maintained normal climb and cruise rpm. Did four landings and at each touch and go, engine stumbled again same way. Mag checked out ok both on run up and at cruise power (2500rpm) and altitude. By the way out of four landings and takeoffs one was acceptable to this old Bonanzas pilot! Good thing my instructor, who has lots of time in taildraggers, owns and flys a Texan T-6 has a great sense of humor! Thanks in advance for comments.

Have you played around with the mixture?

Is this something new? If so, what were the conditions when it did not happen? Do you know if your carburetor has the single piece venturi? (Check your AD compliance list).

I know Randy will chime in soon, IIRC there can be a lag between the idle and main circuit on the Marvel Scheb but I don't recall the rpm range. I had something similar, but it turned out to be instead a float level thing.

Just a thought and something else to check. IF you have the correct carburetor for the O-200 it should have an accelerator pump. I’ve seen the pump ends get hard with age and not push gas into the circuit.
JMHO, Steve

I agree with Steve. There is a fuel flow deficiency. It could be from the source, thru the gascolater or thru the carburetor. There is a screen where the fuel line goes into the carburetor. You might check that for a partial blockage.

I’ve had same problem with mine it’s a C-85. It’s the way the stromberg carb works. If you add power slowly it won’t stumble.