OMG I have to tune a CNS!!! Help

Not easily. The carb has YD cast into it. Idle adj. screw and mixture adj. screw (closest to air filter and capped off) and the letters C-32CNS66EPA on the fuel bowl. (I think the first letter is C...It's kinda smeared)
 
JCG said:
I got a new CNS carb with my bike kit. Capped off mixture screw, only one slot on needle for e-clip. Starts good, idles good, ok power on the low end , NO POWER at mid range to full throttle. (bogs down) I can take the cap off the mixture screw. Now what? Where should the float be adjusted?
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You should warm up the motor and then do a plug chop while riding in the region that you are experiencing bogg. Then let the motor cool down and pull the plug and examine it to try and determine what condition is causing the bogg...

Here is a very handy guide to help you read the spark plug and determine the condition. After you decide if it is running lean or rich then we will know how to adjust....

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Also, an easier test you can do with the CNS to determine if its running lean or rich... Warm up bike, ride into the range where the bogging occurs, while bogging pull on the Enrichment Jet (choke lever), if the bogging goes away or is reduced then the bogging was caused by a lean condition (since the Enrichment jet added extra fuel and richened the mix), if the bogging continues or worsens with the choke lever pulled then you are too rich already....
 
they cap off the mixture screw because EPA regulations mandate it, to keep people from adjusting them richer and spewing unburnt hydrocarbons into the air.
 
JCG said:
How do you adjust the mixture with the screw capped off and only one notch on the needle?
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I would look into determining what adjustment in the mixture need be made before worrying about how it can be done. The cap on the air mix screw can be popped off and the screw is there below, but the air mixture screw adjustment isn't going to cure a situation where it runs good at low RPM and boggs at mid to full throttle...
 
just find a needle from a nt carb, or if its lean you can look into some small spacers to put under the clip on the need and raise it up. i think the spacers from the shocks of a RC truck could work.
 
Like was said above check your spark plug color, it should be light to med. brown. Also you can try a test run without the air filter and see if that helps, if so it is running rich.
 
Ok ...I did the test. Ran worse with the choke on. Spark plug was wet and had oil on it. Ran better with the air cleaner off. When I rev the motor with air cleaner off, A little fuel mist(????) come out of the carb. I guess it sounds like it's running rich. What's the fix?
 
If you know how to solder up the jet its an easy fix, if not you will have to order a jet. I think sbp has them. You will need to know which size you have now. If you have a micro drill bit set check which bit fits tight in the jet then solder it up and redrill it a couple sizes smaller. Remember, the higher the number the smaller the drill size.
 
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Don't know the jet size. My bits only go to # 60 and it's too big. We're talking about the bigger main jet...right? Also the bowl vent tube is always filled with gas. I have it in an up turned position so as not to spew gas all over my bike and leg. Is this normal? And.....why should I need a new jet on a brand new carb? Why wouldn't it have the correct jet to make it run right in the first place. Would this carb work at a higher elev.? I live at sea level
 
JCG said:
Don't know the jet size. My bits only go to # 60 and it's too big. We're talking about the bigger main jet...right? Also the bowl vent tube is always filled with gas. I have it in an up turned position so as not to spew gas all over my bike and leg. Is this normal? And.....why should I need a new jet on a brand new carb? Why wouldn't it have the correct jet to make it run right in the first place. Would this carb work at a higher elev.? I live at sea level
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If the vent is full of gas the float level is too high or debris is holding the needle off the seat under the float. I got my drill set from amazon for less than ten bucks shipped, it has a hand drill which looks like a ink pen. We are talking about a smaller jet, my stock jet was a #71 drill bit size. Fix the float problem first then the jet. Does the carb have the vent tube going to the back of the air cleaner? If so pull it out and try a test run.
 
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Are there any specs on the float adj. or is it just trial and error? The vent tube doesn't go to the back of the air cleaner. It just hangs down. Like I said, I have it turned up to keep the gas from spewing everywhere. Here's a picture with the air cleaner off. (note fuel level in tube) It seems odd that the carb isn't level, but all the bikes I've seen on this site and others seem to be about the same angle.
 

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JCG said:
Ok ...I did the test. Ran worse with the choke on. Spark plug was wet and had oil on it. Ran better with the air cleaner off. When I rev the motor with air cleaner off, A little fuel mist(????) come out of the carb. I guess it sounds like it's running rich. What's the fix?
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A little blowback from the carb is to be expected RE: mist.

If you're running rich at WOT, you could change the jet size (either different jet, or soldering up and drilling back your old one smaller as suggested), but my experience with the CNS says you can probably fix her up with a float adjustment. Mine was running super rich and the float adjustment leaned her out... You want to bend the tab on the float that pushes up on the needle valve, bend it toward the needle valve so it closes the valve sooner (when the float is lower in the bowl). Small adjustments are needed, not big ones.
 
What you have tied up is the bowl over flow, the vent is the tube on top of the carb closest to the air filter. So check the float, it is set wrong.
 
JCG said:
Don't know the jet size. My bits only go to # 60 and it's too big. We're talking about the bigger main jet...right? Also the bowl vent tube is always filled with gas. I have it in an up turned position so as not to spew gas all over my bike and leg. Is this normal? And.....why should I need a new jet on a brand new carb? Why wouldn't it have the correct jet to make it run right in the first place. Would this carb work at a higher elev.? I live at sea level
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Like I and others have said, you need to adjust your float so it closes the needle valve when the float is lower in the bowl. The rich condition and the fuel in the overflow indicate that your float needs adjustment. Once the float is set to hold a lower fuel level in the bowl the overflow tube will be empty and the rich condition will lighten up. The main jet is the biggest of the 3 jets, yes....
When you reassemble the float make sure you put the pointed side of the needle into the valve... Just make a small adjustment and then check it out, it should only take a try or two to get a feel for it and get it set right.
 
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Well I adjusted the float about 10 times. Very small increments. First 1/64ths. Then .030 - .040. Here's what happened.....gas kept coming out of the overflow until finally I had it so tight the bowl wouldn't fill. So I backed it off just a hair and the overflow started spewing again. I never got it running right. At one point it would only run with the choke wide open. So I opened it just a hair and the overflow spewed again. Unfortunately,all this is now moot because I took the carb on and off so many times that it cracked at the mounting ring and now I need a new one. What do you suggest I get? It's a 66cc Gt5
 
Sorry to hear that! You can order a basic nt from ebay for under 15$ shipped. Did you ever remove the needle and check for debris between the needle and seat?
 
Yes I did. No debris. I tried JB weld on the carb. I doubt it will work but its worth a try. Do you know the link for the $15 nt? Still cant figure why I had so much trouble with the cns
 
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