Board Thread:Questions and Answers/@comment-173.198.171.132-20130815192422/@comment-8607467-20130818161520

try this it works for me it will bring up the gui though

java -Xmx2G -Xms2G - jar TekkitLite.jar

pause

Also you cant just change the ram setting though the launcher because its a sever hes trying to do. the launcher only says how much ram the client would have which is fine if playing single player.