Help! KTM440 won't idle ! - KTM Forums: KTM Motorcycle Forum

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post #1 of 31 (permalink) Old 11-14-2012, 12:49 PM Thread Starter
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Help! KTM440 won't idle !

hey all, just acquired a 1994 KTM 440. All I have to say is OMG this bike has insane power ! It rips through each gear, lots of compression, and no stalling or problems when I rev it. However, the dang thing will NOT idle if I let it sit on its own. I have to keep the throttle cracked for it it idle. As soon as I let off the throttle, she stumbles and dies.

I pulled the carbs and cleaned every nook and cranny, including the jets, floats, etc. The carb actually look REALLY clean, but I cleaned it anyway. So I know it's not a clogged pilot jet causing the problem. I also put in a new plug...but I used an Autolite plug instead of the NGK because Napa didn't have it. I will be installing a NGK soon, but I don't think it's the soul cause of the rough idle. I put in fresh 91 octane with synthetic Motul, so I know it's not bad gas.

The only thing I could think of is possibly bad reeds. I haven't pulled the old ones out yet, but judging by the air filter and plug (and lack of previous owner maintenance) I would assume that the reeds are ruined. My question is, could bad reeds actually cause no idle/stalling issues? My bike runs GREAT, it just won't idle at all. I even set the air screw on the carb.
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post #2 of 31 (permalink) Old 11-14-2012, 03:06 PM
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You'll get blow back in the airbox if the reeds are bad, so thats easy to look for when examining things.

Umm, you should have an idle screw on that thing, little black guy. That opens up the throttle plate slightly and gives it more air. Don't mess with the air screw because that has a different agenda.

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post #3 of 31 (permalink) Old 11-15-2012, 08:03 AM
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Sounds like an air leak on a carb boot.

2011 Husaberg TE 300
2008 KTM 950 Super Enduro R
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2004 BMW 1150 RT

Past Rides
'06 Ducati 1000S Multistrada DS (SOLD)
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'95 KTM 620 RXC (SOLD)
'90 KTM 500 MX (SOLD)
'88 Yamaha TT600 (SOLD)
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post #4 of 31 (permalink) Old 11-15-2012, 11:42 AM
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Usually too much air (cracked boot) has the reverse effect, causing the motor to spin out of control without being on the throttle. Usually stalling when opening the throttle and running normally everywhere else, is a carb issue. But I have been wrong before! LOL

2013 250SX-F
2009 Duke 690 (sold)
2007 144sx (150 build)


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post #5 of 31 (permalink) Old 11-21-2012, 12:53 PM Thread Starter
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ok....slowly getting somewhere. pulled the jets, only to find they are WAY too small for the current setup (pipes and air filter/pro reeds). It had a 48 pilot jet and 170 main. According to my manual, they came STOCK with 52/185. So I bought the 52/185 jets and installed them. Just to start as a base. I got it to idle for a little bit, but then it died. It still revs fine...no bogging or hiccups when hitting the throttle...just no idle...unless I crack the throttle just a little. I left the choke up/on and she idled fine, until I put the choke off. Obviously it's starving for fuel.

So, first question, what jets should I try next, considering I have a race pipe (FMF) and reeds/air filter ? it has 52/185 now, which is stock, so I'm thinking 60/190 ? Or should I try bigger?

Next part. I took the petcock off only to find the reserve pipe completely snapped off ! Not sure if this pipe draws in fuel for BOTH on position AND reserve, but the pipe was broken. Filters looked super clean. Nonetheless, I ordered a new petcock. I'm leaning towards this being the actual issue, and not the jets. Because a non functional pet cock will cease full gas flow to the carbs.

Any ideas ?

edit: sometimes it pops/backfires out of the exhaust pipe (just once) when trying to kick it over.

Last edited by slothman; 11-21-2012 at 01:00 PM.
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post #6 of 31 (permalink) Old 11-21-2012, 12:55 PM Thread Starter
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also, I looked all over the carbs....and it doesn't have any black knob idle screw to adjust the idle ! I just see the bigger air idle screw, and the smaller idle screw.
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post #7 of 31 (permalink) Old 11-21-2012, 01:59 PM
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I know you said you have "fresh" 91 in her but,,,fresh 91 is laced with "ethanol",,,,start by pouring in some "Startron " ethanol treatment,,, all my two strokes run like crap without it,,,,,,,
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post #8 of 31 (permalink) Old 11-21-2012, 02:51 PM Thread Starter
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Quote:
Originally Posted by maddog53 View Post
I know you said you have "fresh" 91 in her but,,,fresh 91 is laced with "ethanol",,,,start by pouring in some "Startron " ethanol treatment,,, all my two strokes run like crap without it,,,,,,,
I really doubt that's the issue. Most US fuel now a days contains 5-10% ethanol. Especially Chevron (I hear they have more like 10-15 %). But my other bikes run fuel, with the same fuel, from the same exact station.
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post #9 of 31 (permalink) Old 11-21-2012, 04:25 PM
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Again, there should be an idle screw on the carb. You should be able to just kick up the idle.

If not, then the air screw is clogged somehow and isn't letting air through.

Not enough fuel causes it to bog at higher RPM, too much fuel causes it to bog at lower RPM. Why would it have too much fuel? Because there isn't enough air getting into the system. Not enough air equates to the throttle plate to far closed. The idle screw literally props up the throttle plate, just like what you do with the throttle tube to keep it idling.

2013 250SX-F
2009 Duke 690 (sold)
2007 144sx (150 build)


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post #10 of 31 (permalink) Old 11-21-2012, 04:27 PM
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Quote:
Originally Posted by slothman View Post
edit: sometimes it pops/backfires out of the exhaust pipe (just once) when trying to kick it over.
Backfiring is unburned gas which is ignited out of sequence.

Again, leading to the issue being TOO MUCH FUEL!!!!

2013 250SX-F
2009 Duke 690 (sold)
2007 144sx (150 build)


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