Check your tank stopper to ensure it is sealed... You can pressurize your tank a little and hold it under water and look for bubbles but usually if it's tight enougn you can't spin the stopper.

You mentioned you found the needle valve "broken". How exactly was it broken? Over tightened and stripped, tip broken off, rubber O-ring broken? If the engine was abused in anyway you may never get this thing to run right without extensive repair that may as well constitute a new engine purchace.

I for one have never had an engine damaged by a crash or hard landing but I suppose if you landed on the needle valve assembly it could be part of your problem. Also if you sucked dirt down into the crankcase and ran the engine without disassembly and cleaning this can cause reliability issues as well.