hot weather and LPG.....

ever since it started getting warmer in the mornings my el has been stating really rough on gas and unless i give it a few revs it dies straight away. even then it wants to drop below 500rpm and shudders heaps.
now that its cooled down again it starts perfectly on gas. is this something to do with how its tuned? the type of gas system ive got? something not working?
now that its cooled down again it starts perfectly on gas. is this something to do with how its tuned? the type of gas system ive got? something not working?