I have spent the last 2 days working on a 2007 Eton Viper 90R 4 Stroke, which would only run with the choke on. I disassembled the carb, blew out all of the jets, and passages with compressed air, and checked the float level. I did not find any contamination, or blockages in the carb, but it still would not run without the choke. The carb on this model is different from most carbs that I have worked on, being that the throttle cable opens a butterfly valve, and vaccum lifts the slide, operating the main jet needle.
The idle circuit consists of an air orifice, at the rear of the carb air inlet, a pilot jet, in the bowl, and a fuel screw in the front of the carb.
The air orifice is a fixed size, when the engine is cranked over, vaccum draws air through the orifice, and over the Pilot Jet, and comes out in front of the Throttle Butterfly Plate, into the intake. The Fuel Screw is located in the front of the carb, turning the Fuel Screw in, lowers the amount of fuel, or leans out the mixture, turning it out, adds more fuel, richening the mixture.
What I found out was, the Idle Speed screw, which is located above the linkage, where the throttle cable connects, was screwed in too far, causing the Butterfly Plate, to be opened too far, therefore dropping the amount of Vaccum going through the Idle Orifice, at the rear of the carb.
I actually backed the idle speed screw out until I thought the throttle plate was closed, then the engine started without the choke. I adjusted the fuel screw out 1 1/2 turns, from seated. The engine was idling too fast, and surging a little bit, with the engine running, I backed the idle speed screw out a little more at a time until the idle stabilized.

Hope this info may help somebody else.