Ditto to what Steve and Ryedan posted.
Here is the KayFun users manual which has some great tips:
http://www.meshweaver.com/temp/vaping/SVOEMESTO_KAYFUN_v3.1ES_USER_MANUAL.pdf
Their are numerous ways to "build" for a KayFun so each of us has to find our way for a repeatable and reliable way to build. My own experience and all the threads I have read lead me to suspect a wicking issue as my first suggestion. Here is a pic I did for a friend and although it's not the only way to create a build it helps me explain in pic numbers 4,5, and 6 how important the length of the wick is.
Too long or to short often causes problems. Also, in pic 6, I install the chimney after the wick is cut and saturated with juice. I prefer this way as opposed to threading the wick up through the chimney and then cutting it.
HTH
