I have never run anything but an NT carb on my engines. In fact, the carb I have is my first one and its 3 years old. I have read much of the horrors of tuning problems with the cns carbs and decided I would never buy one. I spend too much time working on my bike as it is. Of course, I'm not spending any more money on my bike until I have the money to install a predator engine on my bike. I finally got tired of dealing with the lack of reliability of the china 2 strokes. Its not if your engine will die, its when. its a waste of money to replace engines every year or two. a predator engine will last for years to come, producing twice the power of a two stroke and still being reliable.
Air leak?
- Thread starter T-lo
- Start date
Well, i couldn't keep my carb on the intake again. the first carb i had broke because it was falling off and the vibration did something and it broke at the screw that goes over the intake. the new v2 carb i got running (not really well) slid off enough for it to run too lean and something jerked pretty bad.
The chain broke - which is nothing new, but hasn't happened since getting the correct alignment, and the chain wasn't loose enough this time for it to jump off.
i havn't taken much apart yet, but i can not get the engine started anymore. something happened and i'm not sure what. I have checked the piston rings and head and i don't see any damage. i changed the spark plug, i have compression. it's still very hard to pedal with the clutch out, but i'm not getting any popping. no go.
i'm a little worried.
The chain broke - which is nothing new, but hasn't happened since getting the correct alignment, and the chain wasn't loose enough this time for it to jump off.
i havn't taken much apart yet, but i can not get the engine started anymore. something happened and i'm not sure what. I have checked the piston rings and head and i don't see any damage. i changed the spark plug, i have compression. it's still very hard to pedal with the clutch out, but i'm not getting any popping. no go.
i'm a little worried.
Ahh, the CNS Version 2 carb with a separate idle air circuit and bogging problems, I know a thing or two about this, wrote a whole pic detailed instructional topic about this very topic I just didn't do here as I was 'banned for life' 2 years ago because I put my local MB business web address in my sig so I joined the other major MB site and shared it there.
New owner here and I'm back but I can't reproduce the whole "Inside the CNS Carb' topic here, sorry, bit I will share this:
Unlike the nonadjustable needle and idle air circuit on the CNS 1, the CNS 2 has both.
Up until the new 2011 models the black rubber gasket inside the carb intake that butts up against you intake was too short to seal the gap in the carb where you tighten the screw to attach it.
This created an air leak leading to a lean condition, so gasket sealer on that grove once the carb was attached fixed that.
Then there is the idle air adjustment screw...
Again I can't go into the whole tutorial with the illustrations of how the 2 different fuel systems work together depending on where the throttle is I can tell you this:
You need to adjust the idle air mix screw on the left and the overall barrel idle screw on the right in concert to get a smooth idle and real power in that idle to 1/2 throttle range where they overlap.
As others have mentioned you can just get an NT carb for ~$20 from BoyGoFast on e-bay but if you have a 66cc motor you will never get the performance a CNS2 will give you, you just won't have to mess with it much.
JUST A WORD OF ADVICE FOR THIS COMMON PROBLEM
DON'T START WITH MODIFYING THE CARB!!!!!
The CNS2 is too much for a 48cc, don't even bother, but for a 66cc, especially a performance one it is the best kit option and they perform great if you just tune it right.
As for specific advice to get going for you T-lo:
Buy an NT carb as there is no telling what your 'carb fixes' did.
Get a couple new plugs and gap them properly, ~.030 give or take .002 depending on your wiring and CDI. The bigger the gap the better if it will still spark at idle. Just like the Aux circuit on the magneto the spark voltage goes up with RPMs.
Once you get it started and warmed with a short ride up kill the motor at Wide Open Throttle (WOT) and THEN check the plug for color.
If it's dark move the needle clip down a notch and try again.
If it's white move it up a notch.
If it's tan stick a fork in it, your good ;-}
New owner here and I'm back but I can't reproduce the whole "Inside the CNS Carb' topic here, sorry, bit I will share this:
Unlike the nonadjustable needle and idle air circuit on the CNS 1, the CNS 2 has both.
Up until the new 2011 models the black rubber gasket inside the carb intake that butts up against you intake was too short to seal the gap in the carb where you tighten the screw to attach it.
This created an air leak leading to a lean condition, so gasket sealer on that grove once the carb was attached fixed that.
Then there is the idle air adjustment screw...
Again I can't go into the whole tutorial with the illustrations of how the 2 different fuel systems work together depending on where the throttle is I can tell you this:
You need to adjust the idle air mix screw on the left and the overall barrel idle screw on the right in concert to get a smooth idle and real power in that idle to 1/2 throttle range where they overlap.
As others have mentioned you can just get an NT carb for ~$20 from BoyGoFast on e-bay but if you have a 66cc motor you will never get the performance a CNS2 will give you, you just won't have to mess with it much.
JUST A WORD OF ADVICE FOR THIS COMMON PROBLEM
DON'T START WITH MODIFYING THE CARB!!!!!
The CNS2 is too much for a 48cc, don't even bother, but for a 66cc, especially a performance one it is the best kit option and they perform great if you just tune it right.
As for specific advice to get going for you T-lo:
Buy an NT carb as there is no telling what your 'carb fixes' did.
Get a couple new plugs and gap them properly, ~.030 give or take .002 depending on your wiring and CDI. The bigger the gap the better if it will still spark at idle. Just like the Aux circuit on the magneto the spark voltage goes up with RPMs.
Once you get it started and warmed with a short ride up kill the motor at Wide Open Throttle (WOT) and THEN check the plug for color.
If it's dark move the needle clip down a notch and try again.
If it's white move it up a notch.
If it's tan stick a fork in it, your good ;-}
opened the magnito cover, WATER!? it was raining, but this was 3 weeks ago!
Ok, would water stop the magnet from sending current to the cdi? maybe cdi got wet and didn't like it? the cdi looks pretty well sealed.
just checked magnito with multimeter. no problems there - needle jumping fine. reseated the plug wire with the boot - no signs foul play there either.
i would like to make an hypothesis. the cdi died. what do you think?
Ok, would water stop the magnet from sending current to the cdi? maybe cdi got wet and didn't like it? the cdi looks pretty well sealed.
just checked magnito with multimeter. no problems there - needle jumping fine. reseated the plug wire with the boot - no signs foul play there either.
i would like to make an hypothesis. the cdi died. what do you think?
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everywhere before the cdi; i get a reading on the multimeter.
from the spark plug wire (alone), the metal part that goes on the plug, and the plug all give me no reading. looks like i'll have to get a new one. and they say boats are pain.
from the spark plug wire (alone), the metal part that goes on the plug, and the plug all give me no reading. looks like i'll have to get a new one. and they say boats are pain.
Ohhh ya, I meant the needle itself not the clip, you move the clip up to move the needle down to lean it ;-}
The only test for a CDI is to put your Ohm meter on ~20K, the red lead on the motor ground (a head bolt is a good place), the black lead to the metal part inside the spark plug cap.
You should get 650-700 Ohms.
If you don't get that check your Magneto to motor ground connection, if it's good then ya, it may be a bad CDI, or it may just be a bad plug wire or iffy motor to CDI connection.