Not really enough information, but it sounds like one of two things.

1- you are trying to idle too low
2- your low speed needle needs to be leaned just a tad, or maybe richened just a tad. Since you say "loads up", I'm assuming the engine is slowly loosing rpms and stopping when at idle, that would indicate it being rich, and you want to lean the low speed needle. Try moving it 1/8th of a turn at a time. very small adjustments are the rule for the low speed needle on most engines.