moonerdizzle
New Member
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.
OMG I have to tune a CNS!!! Help
- Thread starter biknut
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Greg58
Well-Known Member
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
Greg58
Well-Known Member
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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nightcruiser
New Member
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.
nightcruiser
New Member
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
Greg58
Well-Known Member
nightcruiser
New Member
Sounds like you went too lean when it would only run with the choke on... The spacer can be made from a section of PVC pipe for about $1, there is a post in the thread I created about tuning my CNS carb where I detail what I used and how I made my spacer. Check out that thread here....
http://motorbicycling.com/showthread.php?t=32736&highlight=cns+carb+working+great
JB weld on a carb is not a good idea IMHO, you need to be able to remove the carb, not have it permanently attached. The rubber seal in the throat of the carb fits perfectly on the end of the intake and makes a great seal when installed properly (again, read thread linked above). Someone has also detailed how to make the spacer out of copper, but the one I made from PVC water pipe is virtually indestructible, I tried to break it and couldnt....
IF you are lowering the float but still get gas out of the overflow then you have a problem with your needle valve, it is not closing. You need to check it to make sure there is no debris stuck in there preventing it from closing and make sure you put the pointed side of the needle in to the valve. You can check the operation of the needle valve by turning your (clean) carb upside down and blowing through the fuel line. (more details in the post linked above.
I rode the he11 out of mine yesterday, I am extremely happy with how she runs, pulls like he11 from barely rolling right up to top RPM.
http://motorbicycling.com/showthread.php?t=32736&highlight=cns+carb+working+great
JB weld on a carb is not a good idea IMHO, you need to be able to remove the carb, not have it permanently attached. The rubber seal in the throat of the carb fits perfectly on the end of the intake and makes a great seal when installed properly (again, read thread linked above). Someone has also detailed how to make the spacer out of copper, but the one I made from PVC water pipe is virtually indestructible, I tried to break it and couldnt....
IF you are lowering the float but still get gas out of the overflow then you have a problem with your needle valve, it is not closing. You need to check it to make sure there is no debris stuck in there preventing it from closing and make sure you put the pointed side of the needle in to the valve. You can check the operation of the needle valve by turning your (clean) carb upside down and blowing through the fuel line. (more details in the post linked above.
I rode the he11 out of mine yesterday, I am extremely happy with how she runs, pulls like he11 from barely rolling right up to top RPM.
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nightcruiser
New Member
Another thought...
When you pull the bowl make note of where the overflow tube is connected, see that inside the bowl it is connected to a riser tube. The fuel level must reach the top of this tube before it can come out of the overflow.....
If you are getting fuel out of the overflow even when the fuel level in the bowl is low then perhaps this overflow riser tube is not properly seated in the bowl, or perhaps it is defective in some manner (a hole/crack in it) This is not common, but could happen, the fuel inlet nipple wasn't firmly pressed in place on my carb, couple taps and it was all fixed.
Just thought I would throw that out there....
When you pull the bowl make note of where the overflow tube is connected, see that inside the bowl it is connected to a riser tube. The fuel level must reach the top of this tube before it can come out of the overflow.....
If you are getting fuel out of the overflow even when the fuel level in the bowl is low then perhaps this overflow riser tube is not properly seated in the bowl, or perhaps it is defective in some manner (a hole/crack in it) This is not common, but could happen, the fuel inlet nipple wasn't firmly pressed in place on my carb, couple taps and it was all fixed.
Just thought I would throw that out there....
locell
Member
