I took my SS7/Rotax912S/Dynon Flight Dek180 out for its first taxi today. Brakes were good, tail wheel and steering felt good. But when the GPS said I was moving along at 18mph the Dynon IAS said nothing. I have the basic Kitfox pitot tube, not an AOA unit. I disconnected the air tube from the back of the Dynon. I applied air to the pitot tube and heard and felt the air coming out of the other (Dynon) end. I was careful and the supplied air pressure to the pitot tube was very light...as I moved the (Dynon) end of the tube with air coming out close to the "In" port of the Dynon, the IAS moved up to 26mph or so. I have two static ports on either side of the fuselage. There is a "recalibration" function in the dynon under SETUP/AIRSPEED but that didn't help. This seems like such a simple system...how could it not work? I can call Dynon but with the Holiday it won't be until Tuesday and I'd like to keep working on this. Anyone have any ideas?