Have a 9.8 tohastso and after 4 months wouldnt idle.
Bottom line idle jet prone to fouling as are some of the galleries within the carb body.
this reoccurs about every 20-30 hours of use.
to resolve each time remove carb and dissasemble. Clean jets, including side ports, with carb cleaner. I also pole them through with a strand of copper wire. Blow out the various passages in carb body, especially the idle gallery.
use carb cleaner and q tip to clean seat for float neddle valve, this area prone to gunking up.
put back together and reattach, careful with the gaskets.

For preventative I use a off engine seira filter water seperator and add fuel stabalizer everytime I fill.