KQ300cy

So, going back through the things I need again to make her run...spark-good, fuel-good...but decided to check it again... bingo!  At idle, the fuel pump works fine (almost seems like too much fuel), but when given throttle, the fuel flow stops.  Vacuum line going to pump is good, and the diaphragm in the carb looked good...so now where???

The spark is consistent...not a big spark by any means but white and very visible.

Just put a fresh plug in, no change.  I am guessing that the adjustments are fine because it was running good then this issue came up when I was riding it.  I do recall it happening, then it ran fine...then reverted back, and hasn't been the same since.

So, verified that all parts are in the carb correctly, cleaned, and reassemble/installed.  Fired it up again with the same chugging sound...smoothes out a little at idle.  I did remove the charger once started, but same result both ways.  I will try to attach a video of the sound.

Thank you so much for all of the info, the document on the carb breakdown has my exact one included, so thank you!  And the post regarding voltage is interesting...mainly because, my battery is dead, an I am starting it with and have my charger connected to it until the battery is replaced.  Surely is is getting a higher voltage...i will check it out.

Hi all, new to the forum, looking forward to getting some help/advice on maintaining an 18 yr old atv!  So my King Quad 300, recently started running really rough (otherwise ok til this point) at anything more than idle.  After started, choke on/off, doesn't seem to matter, it shutters (Not sure how else to explain it) really bad when given throttle.  I can let the engine run for several minutes, but this never improves.  

Fuel pump checks out ok, and I don't see any gas in the fuel pump vacuum line.  I am a novice on a carburetor, but I need to see what's going on, so after taking it apart, I have a question about this plastic part with an o-ring that is above the jet needle.  Appears as if someone rebuilt this carb, because it is extremely clean...so I am wondering if this plastic part looks to be typical for this carb...or not.  Thanks in advance for the help!