bigted, following Bruce's advice, I suggest you start with items 54 and, especially, 55 on the Illustrated Parts List in the WT manual here:
http://www.walbro.com/media/21907/WTseries.pdf

If that does not fix the problem, it will be time to set the metering lever height, inspect the needle, etc. and go through the process as detailed in the manual. Please keep us posted as you go - hopefully we can help if you get stuck. And be careful when you remove the metering lever - last time I did one the little spring pinged into the distance and it took me 20 minutes to find it.