Tuning CNS High Perf Carb

I am having the same problem I can't find any info on this other than a picture. I have tubes running nowhere and I haven't the slightest clue what to do

If you search tuning the cns in the search box near the top of the page you can find all kinds of info on the cns Carbs.

When I click the search button I can type one letter then it disappears

Are you using a phone? I use mine sometimes and it works for me, its better on my kindle because us old guys cant see! Click on the search box first then type what you are looking for the click the search button.

I'm going to take a shot in the dark here and say something is clogged.

Pull your fuel line off the carb, with a tray under it, turn on the petcock on the tank. Gas should flow out pretty well.

If it does, pull the bowl on the carb. Gas? Good. No gas? Bad. Little gas? Also bad.

If it seems like the bowl has a good amount of fuel, I would remove the main jet (it's that fat sucker in there) and try to blow it out good.

This is all I can think of off the top of my head. I will likely be getting one of these carbs soon as mine is cracked. :\

I had a new Skyhawk kit motor with the same problem today, what can happen sometime in shipping is the needle that attaches to the float arm get jammed.
This can lead to no gas or too much indicated by fuel in the overflow hose at the bottom.

The 2 other hoses are air vent hoses for the main and idle carb circuits, do NOT plug or otherwise mess with them, just tuck them in between the 2 cables from the carb top.

To see if your float is working pull the top off, loosen the clamp bolt and pull the carb off keeping it level so you don't spill the fuel in it.
Holding it level unscrew the bowl nuts and drop it out, it should be a good 95% full of fuel.

Another common issue is simply not mounting the carb on all the way properly.
There is a grove where the bolt to tighten the carb is on the top, this needs to spread wide with a flat head screwdriver before you even start.
Then there is a plastic insert with a grove, put that grove down, hence opposite the carbs grove.

Slide the carb on until the intake pipe is up against the rubber gasket in the carb and then tighten it down good.

Also note that with any carb they are gravity fed and need to be level, if you mounted your motor so the carb is over about 10 degrees off level it will always fail.

KCvale said:

I had a new Skyhawk kit motor with the same problem today, what can happen sometime in shipping is the needle that attaches to the float arm get jammed.
This can lead to no gas or too much indicated by fuel in the overflow hose at the bottom.

The 2 other hoses are air vent hoses for the main and idle carb circuits, do NOT plug or otherwise mess with them, just tuck them in between the 2 cables from the carb top.

To see if your float is working pull the top off, loosen the clamp bolt and pull the carb off keeping it level so you don't spill the fuel in it.
Holding it level unscrew the bowl nuts and drop it out, it should be a good 95% full of fuel.

Another common issue is simply not mounting the carb on all the way properly.
There is a grove where the bolt to tighten the carb is on the top, this needs to spread wide with a flat head screwdriver before you even start.
Then there is a plastic insert with a grove, put that grove down, hence opposite the carbs grove.

Slide the carb on until the intake pipe is up against the rubber gasket in the carb and then tighten it down good.

Also note that with any carb they are gravity fed and need to be level, if you mounted your motor so the carb is over about 10 degrees off level it will always fail.

Click to expand...

Good to know. Thread jack here, but what do you think of the offset intake offered by multiple vendors?

dodge dude94 said:

Good to know. Thread jack here, but what do you think of the offset intake offered by multiple vendors?

Click to expand...

All I buy are Skyhawks which come with the Z pipe and I like them just fine.

Read what KCvale has to say he knows skyhawks plus check the gas cap for venting right. Pull the fuel line off that attaches to the carb and turn petcock on and make sure fuel is coming out in a little stream if so that's not the problem.

I run the CNS V2 carb and am very happy with it, so I will throw out anything I've learned that I think will help you....

First of all, know your carb! The CNS has 3 jets (as opposed to the standard carb with only has 1 jet), a main jet, an idle jet and an enrichment jet (choke). The idle jet (inside the tube next to the main jet) is very small and clogs easily, if it gets clogged you will have hard start and rough low RPM riding. Mounting your CNS is a bit different too. The white plastic ring, contrary to popular belief is NOT the seal, its simply a bushing. Inside the throat of your carb there should be a black rubber SEAL that is form fit on one side for the carb, and the other side is formed to fit OVER the end of the intake. You MUST seat the carb all the way down on the intake and INTO that rubber seal to mount it properly. So pry the neck of the carb open a bit, push it on until it bottoms out, then wiggle it around a bit while pushing it on to seat it that last little bit INTO that rubber seal. (pull the seal out and inspect it to see how it is supposed to mate to the intake) When you tighten the mounting screw make sure you are pressing the carb firmly onto the intake, if you do this you should not have a leak at the carb/intake junction. If your carb is not sealed on the intake it will not draw fuel properly.
Since you said the plug looked dry I would say look for air leaks at the intake, exhaust and at the head (is the head torqued down properly?) I would also look for clogged fuel filter in your petcock, frankly I would tell you to remove that fuel filter all together and run an inline fuel filter instead. You can check if your fuel flow is restricted by removing the fuel line and letting fuel flow or even better you can remove the drain screw from the bottom of the carb and see if fuel flows out of it (this will tell you if your needle valve is clogged).
The float has a HUGE effect on how the CNS carb runs, you adjust the float by bending a little metal tab on it that pushes up on the needle valve. If your carb is too rich try adjusting the float to close earlier and hold less fuel in the bowl, if your lean then adjust to hold more fuel in the bowl. The float is a rather simple mechanism, pull the bowl and there it is, one screw holds it in place. You should see where the metal tab pushes on the needle valve. Inside the needle valve is a little part (don't know the name) that will fall out, the pointed end of this part goes INTO the valve and chokes off fuel flow when it gets pressed by the float. Make sure this part is moving freely (not jammed)
Don't worry about all those hoses, they are hoses to nowhere....

EDIT: I find I dont need much "choke" to get my motor running, not long after it has started up the motor does not like to idle with the enrichment jet open. So make sure before you back down to idle you try turning off the choke.

I've read that the extra hoses shouldn't be plugged as they are vent hoses for the various areas that need venting.


And just to throw this out there, my bike only needs to be choked if I haven't ridden in more than 2 days. Just needs that little extra bit of fuel to pop over, then it's roaring.