NT carb won't idle right

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GreedyRogue

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Feb 15, 2011
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I have a 66cc gt5 that came with a cns v2. Since I couldn't tune that, I bought an nt carb to replace it. I got the rubber o-ring with it to help with air leaks.

Got it mounted and started and the idle was too low. To get the idle anywhere near proper, I had to screw the idle in so far it put a dent in the needle. Contacted the seller, did a few diagnostic tests and was sent a new one free of charge. (Thanks Dax!!!!)

Im having the same issue with the new carb. I even replaced the main jet with a #66 I had to try getting more flow. The screw is in as far as the spring will allow, the slide is up quite a bit, and it still idles so low it actually died when I came to a stop sign yesterday. Here's some pics to show you what I'm talking about.

The first pic is with the screw tightened with the spring still on, not far enough to hit the needle.

I have built 2 other 66cc's with nt carbs and didn't have an issue like this. Any ideas?

 
Pilotgeek

Pilotgeek

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Apr 6, 2011
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Does it run fine when it's not idling? Have you checked plugs to make sure the mixture is alright? If you're running anything off the white wire, that can also make idle difficult.
 
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GreedyRogue

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When riding the bike it is a little slow to accel, but I have the full range up to about 28-29 mph. Haven't checked the plug yet as I just got it on yesterday, and nothing on the white wire.

The c-clip is currently on the second notch down and seems to run fine. A plug chop wouldn't hurt though.
 
Pilotgeek

Pilotgeek

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I personally just had to replace a carb due to tabs breaking off where it meets the intake. It was not idling right for a while due to an air leak.
 
timboellner

timboellner

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Sometimes when you have an air leak it will only idle with the choke on, try that.
Air leaks don't necessarily always only come from the carburetor.

Since the fuel mixture is pulled into the crankcase from the carb it is possible that you may have an air leak in several other places.
The cylinder jug gasket, the crankcase gasket ( separates the left and right side of the engine block), the left side or the right side round rubber crankshaft seals located behind the magneto magnet on left, and small bevel gear on the right side.
These engines were probably not assembled by people who actually give a rats a$$
TiM
 
bairdco

bairdco

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Aug 18, 2009
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the idle screw should never contact the needle. it pushes against an angled groove on the slide which raises it.

with the idle screw out, the slide on the NT should sit all the way down in the carb, covering the throat. when the screw is turned in, it'll slightly raise it up until you find the right setting.

if you screw the idle all the way in (don't foce it, just till it stops,) the factory setting is 3.5 full turns out.

from your pictures, it looks like your slide isn't going all the way down.

if the slide is raised like that and it won't idle, i'd definitely look for an airleak. it should be revving super-high otherwise.

also, this may sound stupid, but make sure your choke's all the way off after warm up.
 
ToxicAz520

ToxicAz520

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Mar 11, 2011
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i agree with the rest of the experts here it maybe an air leak from somwhere else def try the choke cleaner like u said and let us kno wat u find cause the idle screw should never be all the way in.
 
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GreedyRogue

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Couple posts to reply to here so lets see if i get it all.

Haven't tried the carb cleaner on the new carb yet, but I will here in an hour or so.

With the first carb I sprayed the entire engine, top to bottom, and no bogging or revving.

The slide works fine, the pics are just to illustrate how far up the slide is just to keep it running. Lower than that and the thing dies.

It's warm enough here that I have never had to use the choke more than 1 city block, and it will not idle or run with the choke on.
 
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GreedyRogue

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Ok, did the carb cleaner and found out I have 2 air leaks, both on the carb.

First is on the carb to intake, second is the cable inlet at the top. I can fix the cable with a small o-ring , but how do I fix the intake?

I already have an o-ring there to stop the airleaks, but that did no good. Even tried taking the o-ring out and still have a leak.

Funny thing is, the first carb didn't have any dying issue when I sprayed it with cleaner, but this one does. Yet both had an air leak.
 
hawaii_87

hawaii_87

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May 17, 2011
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I have the same issue except the bike revs like **** after I give it a lil gas. It will just keep going and sounds like its going to explode and just does not idle.
 
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