KX250....30 sec of idle kills motor

[/J/]

Ok, the bike has done this since I got it. I've just accepted it, figuring the pilot may not the right size. I've always just blipped the throttle when "idling" to prevent it.

But how likely is it that it is instead partially gummed up? RC5Juan, did the bike ever sit for a while when you had it?

I want to fix it...it'd be nice to be able to let it idle for as long as necessary (especially on trails).

[420]

2-stroke? They don't idle well, if so...

You can set them via air screw for a certain air density, but that changes frequently.

[zman]

True 2 smokes and Idle dont mix

It could be the pilot gummed up tho also

[Indetrucks]

IMO a 2 stroke shouldn't idle for more than 20/30 seconds. You just end up loading the thing up and risk fouling the plug.
Keep that bitch reving.

[/J/]

What you guys are saying is what I previously thought. But I was talking with an experienced rider/owner of many bikes and he was of the opinion that they should be able to idle at least a little bit successfully and I guess it made me forget about all of what you guys are saying.

[Nocontrol]

should be able to idle and idle and idle, not that you should, but it should be able to

id pull the carb, disassemble and let it soak in a bucket of carb cleaner (1gallon can with parts bin you can get at autoparts stores), usually gets the pesky stuff unstuck

[Earl]

My YZ125 and WR250 will idle w/o any problems, after being warmed up.

Sounds like you need to readjust the air screw.

[RC-5Juan]

I always drained the carb after i rode it. Never had issues with stalling. Ill see if i can help ya out next time we are out together.

[420]

2-Strokes in general do not idle well. As I mentioned, you can adjust your air screw to set the idle for wherever you are at, but whether it maintains that setting has alot to do with the air density at where you are riding on that particular day. 2-Strokes are very finicky to air and fuel/oil. Changes in humidity, heat, barometric pressure can have major effects on how they run. Though my dirt bikes seem to have alot less problems than my roadrace bikes.

Also if you are gonna ride your bike relatively soon, it probably better to keep the gas in the carb (not run it out). This keeps the floats in alignment and we have noticed over time the carb needs less maintainence. It takes a while for the oil to break down and gum up the carb.

[SWAMPY]

My bike has been set up to idle as long as possible so it will not kill the 200 or so times I drop it every time I ride. Set the air screw to see if you need a larger or smaller pilot. I would run a newer pug when doing this. Keep in mind weather and altitude will have effects on the settings. Most two strokes I have purchased have been set up to run on the richer side of the spectrum which is better than a lean situation generally.
Adapted from www.all-offroad.com.


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Keihin Carburetion Jetting
AIR SCREW:
The air screw is a small (5mm in diameter) slotted brass adjustment screw located on the inlet side (air filter side) of the carburetor. The airscrew is a fine-tuning adjustment designed to allow the carburetor to be slightly adjusted for variances in atmospheric conditions. The airscrew works with the pilot/slow speed system of the carburetor, mainly affecting the engines initial starting, idling and initial power delivery. Proper adjustment of the airscrew can offer direct feed back on the necessary setting required for the pilot jet. The airscrew is adjusted in a rather straightforward manor.

The ideal procedure for setting the screw in the correct position is to warm up your ATV engine to the proper operating temperature. Then turn the idle up so it is idling about 500 RPM’s higher than normal. Next turn the airscrew all the way in until it bottoms out, once bottomed out slowly back the screw out a ¼ turn at a time (give the engine 10-15 seconds between each ¼ turn of the screw, to allow the engine to catch up with the adjustments). Continue backing the airscrew out until the engine idles at its highest RPM. The preferred setting window is between 1 and 2 turns. If the engine idles at its highest RPM from 0-1 turns out this means the pilot setting is on the Lean side and a larger pilot jet should be installed. If the engine idles at its highest RPM at over 2 turns out, this means the pilot setting is on the Rich side and a smaller pilot jet should be installed.

If you get no RPM fluctuation when adjusting the air screw there is a very realistic chance that there is something clogging the pilot/slow speed system. Clean the system thoroughly with contact cleaner and blow out with compressed air. Carburetor must be disassembled.

If the airscrew adjustment process is unsuccessful and leaves you confused. Set the screw at 1 ½ turns out and consult a professional for further assistance.

PILOT JET:
The pilot jet is a medium size (¾-1”) brass jet located inside the float bowl next to the needle jet/main jet location. The pilot jet meters the fuel required for engine starting, idling and the initial throttle opening 0-1/8.

A lean pilot jet setting will cause your engine to surge at very low RPM’s, bog or cut-out when the throttle is opened quickly and have trouble idling down.

A rich pilot setting will result in hard starting, plug fouling at low RPM’s, sputtering as the throttle is cracked opened.

The pilot jet is not difficult to set. With proper air screw adjustment and a close initial setting from your engine tuner, fine-tuning should be painless. Once set the pilot jet is not terribly sensitive. You should only be required to adjust the setting when confronted with large weather changes or altitude swings of over 2000 ft.

If adjusting the pilot jet gives inconsistent feed back, or does unexplainable things. Check and clean out the pilot/slow speed system thoroughly with contact cleaner and blow out with compressed air.

[/J/]

Thanks Swampy. I've also read the two-smoke tuning guide that was posted on Thumpertalk a while back...only used that to mess with the NSR50R I had. I will play with the KX carb on Saturday!

[Earl]

Thanks Swampy. I've also read the two-smoke tuning guide that was posted on Thumpertalk a while back...only used that to mess with the NSR50R I had. I will play with the KX carb on Saturday!

You might want to take the pilot and main jets out and see what you have in there and compare to what the manual specs.

We can also tune it Sun, if you come out and play!

[/J/]

The jets should be stock unless RC5Juan ever changed them out. Juan?

I plan to be out on Sunday!

[RC-5Juan]

I did change them out when we went to KM. I believe I changed them back to what was in it when I bought it though when we got back.

[zman]

if all else fails bring carb cleaner , sewing needles and jets out to CE
i bet we can make her sing again :thumb

[Sidewinder]

J, I had a KX 250 for 6 years. They are finicky. Keep on blipping that throttle and you'll be fine!!

[Sex Machine]

mine will idle for roughly 10-15 seconds before it does. If I adjust the air screw it'll idle longer probably. No need though. not like it's hard to start a 2 stroke lol.

[Earl]

I plan to be out on Sunday!

Cool, I'll have some carb cleaner with me, I always put some in before I ride to keep things clean.