I assume by air hose screw he means the adjustment screw for the throttle cable thats on the air hose/throttle housing.
You could pop the back off the carb and flip the top of the diaphragm aside and check that when you move the cable that the grey thing inside the carb gets its full range of movement.
Some wont start on the choke, ive had a few like that.
Id assume that a plastic carb as it came from Victa is pretty well sorted. Anything that doesnt work right has had work shop improvements. Theres no way you could get half the replacemnt parts, theres heap of different spring combos.
