chainsaw?

i have a homlite chainsaw and sometimes it starts first time but not very often most of the time it wont start at all i have checked the fuel the sparkplug.when i took the spark plug out the plug and carb were completely dry but i had been trying to start it prior to doing this when i have been pulling on the cord then open up the fuel cap there is a biuld up of pressure in the tank and when it does start if it stops it is a pig to start again can any one help me