I've been flying my Sig Senior Kadet w/K&B .61 2C for a couple months now with good luck... The other day I dinged the nose strut on a hard landing and had to replace it and add some plywood to the firewall to reinforce it... Nothing major, just part of the game... After the repair, I successfully flew the airplane one time... On the next flight, everything was going well until I went full throttle in the air... The engire ran fine at first, then after 2 - 3 seconds it leaned out and died.... I was able to get back on the ground dead-stick without damage... I chalked it up to experience, refueled and tried again... This time, when I took off I got to about 50' AGL at full throttle and the engine leaned out and sputtered... I throttled back and the engine returned to idle, but wouldn't throttle up again, just sputtered and died... I was barely able to get back on the ground in one piece... I then put the airplane on the test stand and duplicated the problem... The engine starts fine, runs fine at low RPM, but when I throttle up it runs fine for 2 - 3 seconds and then dies...

I replaced all fuel lines... Still does it...

I reset to a richer mixture... Still does it...

I checked the clunk in the tank... Attached and functional... Still does it...

I'm at a loss...

Any ideas???

Thanks,

Mark