Hanging Idle

S

Snoboardcore

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Nov 17, 2007
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When ever i come to a stop the idle hangs around 3,000rpm if i hit the throttle real quick it will come down to 2,500rpm then about 10 seconds after will come down to 2,000 what could be causing this? Also the carbs are clean and it has a brand new top end 125 miles ago.
 
Yes you could try that,you'll have to pull the carbs off and look underneith
and you'll see the screw's, stock is 1 1/8 so you could try 1 1/2-1 3/4,also
have your idle around 1,650-1,700 rpm's.

here's your screw's;

scan0001-2.jpg


post back with your results..
 
Hanging idle

My 2002 viper was doing exactly what you described! I called a dealership and he told me to adjust the idle screw just enough to slow the idle a tiny bit.... and so far i have not had the problem again!!
 
I am dealing with this issue as well.
I have searched high and low. There are many posts on the topic but not a lot for solutions. I have tried everything I have read in the post from checking for air leaks, changing pilots, returning my air box to stock, using mutiple fuel screw settings (remote adjusters) with all pilot sizes from 45 to 60, needles up and down at all settings. I have found nothing to cure this problem. So either I live with it or I get rid of the pipes and go back to stock.
 
with pipes you surely need bigger pilot jets,add any kind of aggressive clutching and youll need bigger pilot jets, what pipes and what sled are we talking about now?
 
Not to steal the thread but...
01 MM700. Bender pipes, stock springs, little bit of work on the 8CR weights.
The air box is back to stock right now cause I'm grasping at straws. Jetting right now is 50 pilots, 3rd clip on the needles with both washers under (stock) 150 mains fuel screws at 1.5 out (I have went as high as 2.5 out). I am at 2000'.

The clutching is bang on. No performance issues when I am on the throttle. It is just the hanging idle when I stop. It will sit above 3000 for a little while then drop down to 2500 and stay there until I blip the choke. Then it stays down until the next time I stop.

I have my idle set at 1800 warm. I have tried lower and higher for the warm idle. Carbs were synced at 1.2mm. Oil cable is at 21mm. Throttle cable is at 2mm

I have gone through all circuits on the carb for cleanliness. They are so clean they shine.

This problem only occurs when warm. When I first start it it idles just fine.

The jetting, according to plugs, piston wash, and egts all confirm that the 50s, #3 on the needles, and 150 mains is right for me...but the hang is still there.
 
then you need 1 of the following: more fuel screw setting, try 1.75 turns out. if you get to 2 turns out and it hangs when warm then I would use 52.5 pilot jets. Its just simply lean in the pilot circuit thats all, its close but just a tad too lean.

btw- it also helps to make these adjustment on a cold day, as those are the days the idles gonna hang, the air is better and the engine will need more fuel.
 
52.5 is on the rich side. I tried that. All my testing has been done colder than -15degreesC.

It seems like when I fatten the lower end it will foul plugs in the mid.

With 55 pilots I have to run wide open or it fouls. and the idle habg is still there.
 
if you have a idle hang with 55 pilots then you need to readjust your throttle cable, you cant foul plugs with rich pilots and have a idle hang unless your throttle cable is too tight!
 
Throttle cable is within spec. It has 2mm free play.
With the 55 pilots it gets really garbly down low and unless I pin it, it will spit a plug. Like I said, plugs, piston wash, egts confirm.

The slides come down all the way also, so nothing is blocking the linkage. They were all synced for the 5th time last night to 1.2mm.

I am thinking I might try to go back to stock exhaust to see if it goes away. If it does then I can eleminate other issues that may be masking the problem.

I agree with everything You have said (100%) but it just doesn't work...what can I say.
 
You might try checking and make sure the slides on the carbs snap shut when you let off. Could be binding linkage or dirty / frayed throttle cable that does not let off all the way when you release the throttle slowly, but vibration will take care of later..
 
Mine does the same thing-- tried just about everything you did, richened the fuel screws, tried next size up pilots, cleaned carbs, but mines a single pipe. Turned my idle down to 1600 and it doesn't do it as often, but it still does it. It usually comes down with a blip of the throttle now, where it used to need a blip on the choke:dunno:
 
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It doesn't seem to make a difference bringing the idle setting down that much. The other thing is that I would like to keep it for the pipes...but 2500 is too high.
 
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