Piper cub pilot reported loss of power after takeoff; so he returned to departure airport.

Attributes
ACN	1018597
Time
Date	201206
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	J3 Cub
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Flight Plan	None
Component
Aircraft Component	Engine
Person 1
Function	Captain Instructor Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 10000 Flight Crew Type 50
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

[After] takeoff; it became evident that aircraft was not climbing enough to clear trees. I maneuvered the aircraft between obstacles and over the river until gaining sufficient altitude to return for a safe landing. I suspect a stuck valve was the problem in the [continental] A-65.

Original NASA ASRS Text

Title: Piper Cub pilot reported loss of power after takeoff; so he returned to departure airport.

Narrative: [After] takeoff; it became evident that aircraft was not climbing enough to clear trees. I maneuvered the aircraft between obstacles and over the river until gaining sufficient altitude to return for a safe landing. I suspect a stuck valve was the problem in the [Continental] A-65.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.