2001 King Quad 300, carb issues

[KQ300cy]

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!

[Frank Angerano]

Welcome to Quadcrazy! I’ve attached a diagram to help you out.  That should pretty much explain things.   It may not be your exact carb but I can look that up for you in the mean time. 

[Wolds Alpacas]

This is a thread I will follow with interest as I too have recently bought a King Quad 300 and it is in need of some attention due to rough running.  I will be stripping the carb out in due course and cleaning in an ultrasonic cleaner so will let you know how I get on as well (after sorting out another quad)

[Frank Angerano]

Yes That’s great.  Just take your time and make sure you do a thorough job.   I like to use a cheap white pilllow case on my work bench before I get into one. It helps to see any parts as well as the dirt that comes out.  I buy the cheap ones a two pack for $2 bucks at them cheap stores like odd lot or something.   

I also like to use a can of compressed air to blow everything out.  Staples or any office supply place has them.   

[Guest]

Check the charging system. At idle you should see no more than 14.5 volts. Typically the voltage should read about 14.5 volts at 2500 rpm or so, lower at idle. An over charge condition can seem like carburetor issues sometimes. Rule this out first, it will save lots of head scratching. If you don't have a volt meter just unplug the voltage regulator and see if your issues go away,quick and free to check. 

[KQ300cy]

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.

 

[Frank Angerano]

That’s what Quadcrazy is here for! Good luck and keep us posted.  

 

[KQ300cy]

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.

[Frank Angerano]

Fuel/air screw set properly? 

Have you checked the spark ? 

Maybe  maybe a fresh plug?

[KQ300cy]

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.

[Frank Angerano]

Gotcha. Have you checked the spark for good quality ?

[KQ300cy]

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

[Frank Angerano]

That should be enough.   The only thing I really have left is the pick up coil?

[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???

[Frank Angerano]

Maybe a bad fuel pump. The diaphragm is bad.  It’s common.