1999 Polaris Xpress 300 Starting Issue

[Zachary]

Hey guys I have a 99 xpress 300 and I'm having an issue, I rebuilt the engine and it will only start when I put my han over the intake on the car (when I manually choke it), I am not very familiar with plunger chokes.could some one help me understand how this choke is supposed to work and maybe how to ajust it so it works, thanks!

[Mech]

Hi. Well the choke works by sucking extra fuel up out of the float bowl when you pull the choke plunger out, either with a cable or a knob. It draws fuel up and mixes it with air then discharges it through a drilling that comes out between the butterfly and the engine. The fuel will only be drawn up though if the butterfly is fairly well closed. If you open the throttle/butterfly while cranking the cold engine the vacuum decreases and the fuel doesn't get lifted enough to get discharged into the engine. So it's important to have the throttle adjusted well closed off as far as possible, and not to use it till the engine has had a chance to be richened up by a few cranks.

That said.. Did the choke use to work before the engine work ? Are you sure the choke is the problem ? Could it have an air leak into the sump, either a seal or a gasket somewhere, or a leak at the manifold ? One indication of an air leak would be it not idling well, or not being able to adjust the idle mixture rich enough.