Lets talk about my KDX220...

My Thoughts

About 3 months ago I purchased a 220 from an older gentleman that rode it a few times with his young son and then garaged it...

I rode the bike before purchasing, it ran fine and looks like it came off of the showroom floor - it didn't idle properly and gas drained from the carb (overflow line), indicative of a 'gum' problem.

I pulled the carb off and cleaned it, the pilot jet was gunked up pretty badly. Ever since this 'repair', the bike hasn't been quite right - runs rough (but idles). I've taken her apart again, but to no avail, I can't find any residual trash in any of the jets. Canadian Dave has some nice work in here about float/carb adjustments, which I have followed very closely. I don't have a vernier caliper so can't measure the float distance to the base of the carb as recommended, but the float is parallel to the base of the carb when the tab contacts the button on the fuel stop valve or plunger. I still think this is the culprit though, might go buy the right tools in order to confirm that this is the problem.

If not, I'm at a loss?

If you are pretty mechanically inclined, it takes only a few minutes to pull off the carb. I would take it all the way down and soak it overnight in carb cleaner. Be sure not to submerge any plastic/rubber parts in the solution though, as it probably will not be there when you return. Afterwards, rinse it well and carefully inspect all jets/ports/etc. A little compressed air will clear out residual solution nicely. If you don't want to mess with it, then take it to a reputable shop and they can probably do it for $100+/-. I'd check out the literature on this site for jetting recommendations. While you have it apart, you can easily follow the provided recommendations and subsequent checks to be sure the engine isn't running lean so it is right.

Good luck!

More Thoughts

After reading your post again, here are some more thoughts.

My dad had a bass boat many moons ago that had a 'gas' problem. As it turns out, there was trash in the tank that was restricting fuel flow into the carbs. The tank was removed and cleaned, then she ran fine.

The same might be true for your bike. The fuel valve has 2 inlets, 1 for 'on' and another for 'reserve'. The on inlet might be obstructed, I'd drain the tank, pull the fuel valve assembly off, and evaluate. This might be your problem.

What did the spark plug look like when you took it out?

Have you adjusted the air screw yet?

You turn it in to make it richer and turn it out to lean it out.

The air screw effects the low speed circuit.
So I would try adjusting it in or out a bit to see how it changes. Generally the standard setting is 1.5 turns out.

Give it a try.

Something else to consider is your petcock valve. If you are having problems with the bike taking gas and it runs better on reserve, then maybe your petcock assembly is corroded. My brothers XR sat with gas in the tank and carb, and his petcock assembly came out all ate up and gummed from the gas. Just a thought.

Sooooo.... has irhxcbcziuzxs come back with any news?
Have any of the excellent suggestions resulted in a crisp-running KDX for the OP???

Mr. OP....???