OMG I have to tune a CNS!!! Help

[merchant810]

ok the plug made it run very smoothly and i believe were making good progress. Now my chain pops off but ill figure that one out. The main issue i need help with is how it revs to top right away. I think this is a choke issue but not sure. Here is a link on youtube to see how it runs, sorry if its not the best video lol. YouTube - ‪80cc occ chopper issue‬‏

 

[Greg58]

I don't know which rear sprocket you used but the smaller tires on the occ will slow your top speed. As far as the vibration I think all do, Mine was so bad when first built I could not keep the gas tank from turning to one side or the other. Funny thing though after I did the port matching and polished the intake and exhaust manifolds the vibs changed from 27 mph to 32, I don;t know why.

 

[biknut]

ok the plug made it run very smoothly and i believe were making good progress. Now my chain pops off but ill figure that one out. The main issue i need help with is how it revs to top right away. I think this is a choke issue but not sure. Here is a link on youtube to see how it runs, sorry if its not the best video lol. YouTube - ‪80cc occ chopper issue‬‏

Actually I think your video is very effective at letting us know how it's running.
It doesn't sound too bad really. especially compared to the way they are out of the box. At least it will take full throttle. Right now the way your bike is running is already tons better than a lot of people have been able to do with these carbs. I think you need more miles. My bike didn't start running it's best till well after 300 miles,

Good job.

 

[merchant810]

im glad to hear it could just be so new, but is it normal that at 1/4 throttle it still hits max rpm its just like its not going fast enough but i might be expecting to much, is it a good idea with my small tire to put a smaller sprocket on it. I still have to get the performance wire and air filter from sbp so im optimistic. also with these mufflers the baffle is welded in it is it smart to take the baffle out or at least take the cap off or do you need the backpressure when breaking them in. I just hate that i cant cruise at any throttle position without it maxing its rpms its annoying i cant really go far.

 

[Greg58]

You were saying you had chain problems, I saw your chain tensioner on the bottom. From what I do at work you need max. wrap around a gear to get best wear. I have not built an occ maybe BN knows more about the chain problem.

 

[biknut]

im glad to hear it could just be so new, but is it normal that at 1/4 throttle it still hits max rpm its just like its not going fast enough but i might be expecting to much, is it a good idea with my small tire to put a smaller sprocket on it. I still have to get the performance wire and air filter from sbp so im optimistic. also with these mufflers the baffle is welded in it is it smart to take the baffle out or at least take the cap off or do you need the backpressure when breaking them in. I just hate that i cant cruise at any throttle position without it maxing its rpms its annoying i cant really go far.

This is what my muffler looked like inside. I hammered a screwdriver into the shut pipes to open them up a little, and left everything else alone.

 

[Sanction]

ok the plug made it run very smoothly and i believe were making good progress. Now my chain pops off but ill figure that one out. The main issue i need help with is how it revs to top right away. I think this is a choke issue but not sure. Here is a link on youtube to see how it runs, sorry if its not the best video lol. YouTube - ‪80cc occ chopper issue‬‏

Hey Merchant810, It looks like your mid range is 4 stroking. This usually means you are getting too much fuel. I suggest you raise your C-Clip up a notch or two.
Remember: low end is the air and Idle screws, The mid range is adjusted with the C-Clip, and the high end is through the jets.

I too have been following this thread with great interest and have learned allot from the very intelligent members of this forum. I take no credit for this information as I am just regurgitating what the real pro's are saying.

Starting next weekend I will also take on the CNS v2 Carb tuning challenge. Soon with enough of us doing this we can get a close adjustment for others to start with.

Hey biknut and all others doing this tune, would you please include your altitude? Thanks!

 

[biknut]

I'm tuning for about 680' above sea level.

 

[Sanction]

I'm tuning for about 680' above sea level.

Thanks biknut! I am right at 100ft above sea level. I would think our settings would be close.

 

[Sanction]

I thinking now the float has to be about high enough.

You gave the measurement for the first 2 float adjustments, but what is the final measurement you have for your float?

 

[Sanction]

How to tune the CNS V2 Carb. ​

I hope you don't mind Biknut, but I have taken all the information from this thread and compiled it into what I hope will be a quick list for setting up the CNS V2 Carb. to run on the 66cc engine 1000ft above sea level or less. Further testing required for above 1000ft.

1: Raise the float level.
Turn the Carb upside down. There's a seam in roughly the center of the plastic float. adjust the float till the seam is parallel to the sealing surface of the float bowl.

2: For the high end, drill out the main jet.
Buy Machinist bits #64 #65 #66 #67 #68 #69 #70 (Stock jet size is #70)
Drill out the jet one size at a time starting with #69 Test and check for full throttle response and spark plug color. Below 1000ft altitude #65 and #64 seem to be about the right
size. If you drill to large of a hole, fill with solder and re-drill with a smaller
bit.

3: For mid range, adjust the C-Clip on the throttle pin.
(Top is lean and bottom is rich) Again check your spark plug for direction.
Black is lean, white is rich, you want a tan or brown color between.

4: low end or idle.
The air and idle screws on the side of the CNS V2 Carb are for setting the
idle fuel/air mix. First turn the air mix screw (left) all the way in and back it out 1 full turn. To raise the idle turn the idle screw (right) clockwise, counter clockwise to lower the idle. Now fine tune the air screw where your engine runs at it's highest rpm then lower the idle with the idle screw.

Foot note: In some cases, but not all, removing the breather tube from the air filter may result in better performance.

ps: I will gladly edit this information if I have gotten something wrong, or new information is gathered.

 

[biknut]

You gave the measurement for the first 2 float adjustments, but what is the final measurement you have for your float?

This is how I made the final adjustment,

There's a seam in roughly the center of the plastic float. I adjusted the float till the seam was parallel to the sealing surface of the float bowl.

Compared to stock, this made the fuel level slightly higher in the bowl.

 

[Sanction]

This is how I made the final adjustment,

There's a seam in roughly the center of the plastic float. I adjusted the float till the seam was parallel to the sealing surface of the float bowl.

Compared to stock, this made the fuel level slightly higher in the bowl.

ok I edited the list with your final settings for the float.

 

[6cylturbo]

I'm still getting thru break-in time on mine but I can't thank u guys enough for posting all of your hard work here. Thank you!!
Thank you!!Thank you!!Thank you!!Thank you!!

Hopefully when I get things further along I can do the same.

Brian

 

[biknut]

I'm still getting thru break-in time on mine but I can't thank u guys enough for posting all of your hard work here. Thank you!!
Thank you!!Thank you!!Thank you!!Thank you!!

Hopefully when I get things further along I can do the same.

Brian

Maybe as you learn more you will also add to the findings.

I was getting tired of reading about one guy after another saying their bikes wouldn't run, and nothing they could do to the carb would make it run any better, and I'm going to toss this pos$#%t and blablabla.

Hardly anyone ever mentioned the main jet even though at full throttle the main jet is doing most of the gassing.

 

[GearNut]

How to tune the CNS V2 Carb. ​

I hope you don't mind Biknut, but I have taken all the information from this thread and compiled it into what I hope will be a quick list for setting up the CNS V2 Carb. to run on the 66cc engine 1000ft above sea level or less. Further testing required for above 1000ft.

1: Raise the float level.
Turn the Carb upside down. There's a seam in roughly the center of the plastic float. adjust the float till the seam is parallel to the sealing surface of the float bowl.

2: For the high end, drill out the main jet.
Buy Machinist bits #64 #65 #66 #67 #68 #69 #70 (Stock jet size is #70)
Drill out the jet one size at a time starting with #69 Test and check for full throttle response and spark plug color. Below 1000ft altitude #65 and #64 seem to be about the right
size. If you drill to large of a hole, fill with solder and re-drill with a smaller
bit.

3: For mid range, adjust the C-Clip on the throttle pin.
(Top is lean and bottom is rich) Again check your spark plug for direction.
Black is RICH, white is LEAN, you want a tan or brown color between.

4: low end or idle.
The air and idle screws on the side of the CNS V2 Carb are for setting the
idle fuel/air mix. First turn the air mix screw (left) all the way in and back it out 1 full turn. To raise the idle turn the idle screw (right) clockwise, counter clockwise to lower the idle. Now fine tune the air screw where your engine runs at it's highest rpm then lower the idle with the idle screw.

Foot note: In some cases, but not all, removing the breather tube from the air filter may result in better performance.

ps: I will gladly edit this information if I have gotten something wrong, or new information is gathered.

In entry #3, I corrected the spark plug colors in regards to the air/ fuel ratio in red.

 

[Sanction]

Thanks for the correction GearNut! I think a bit of my dyslexia has found it's way into my post.

I was thinking this needs to be at the beginning of the thread. Hey bikenut, can you copy it to your first post or make a link or something?

 

[biknut]

This is Duchess. A beautiful silver blue Micargi-Rover beach cruiser, with a silver Grubee SkyHawk 80. It's only a few hours old now, and has been around the block for about 3 miles so far. It belongs to my friend Corinne.

Here's a close up of the carb.

When I fired this bike up for the first time, a few hours ago, it started easily enough with full choke. After a little warm up, what I noticed was a total lack of power above about a 1/4 throttle. All it will do is bog if you give it any throttle. It can barely get up to 10 mph. After a little screw turning I was at least able to get it to idle pretty good, so I don't think it's leaking air.

That's the total extent of the tuning I've done so far. This carb has a aftermarket air cleaner, but the red plastic one is what came on it.

I've been reading about the typical problems people are having with the CNS carb for months, but this is the first time I've had one in hand. I won't toss it in the trash until it's running good lol.

Based on the comments I've read about this carb, I have to agree. Everyone pretty much nailed the description of the symptoms. What I want to know now is what to do next. Some people claim they've made it work, but the how seems a little vague.

Edit//after a few weeks time and further experience tuning this carb.

How to tune the CNS V2 Carb. ​

I hope you don't mind Biknut, but I have taken all the information from this thread and compiled it into what I hope will be a quick list for setting up the CNS V2 Carb. to run on the 66cc engine 1000ft above sea level or less. Further testing required for above 1000ft.

1: Raise the float level.
Turn the Carb upside down. There's a seam in roughly the center of the plastic float. adjust the float till the seam is parallel to the sealing surface of the float bowl.

2: For the high end, drill out the main jet.
Buy Machinist bits #64 #65 #66 #67 #68 #69 #70 (Stock jet size is #70)
Drill out the jet one size at a time starting with #69 Test and check for full throttle response and spark plug color. Below 1000ft altitude #65 and #64 seem to be about the right
size. If you drill to large of a hole, fill with solder and re-drill with a smaller
bit.

3: For mid range, adjust the C-Clip on the throttle pin.
(Top is lean and bottom is rich) Again check your spark plug for direction.
Black is RICH, White is LEAN, you want a tan or brown color between.

4: low end or idle.
The air and idle screws on the side of the CNS V2 Carb are for setting the
idle fuel/air mix. First turn the air mix screw (left) all the way in and back it out 1 full turn. To raise the idle turn the idle screw (right) clockwise, counter clockwise to lower the idle. Now fine tune the air screw where your engine runs at it's highest rpm then lower the idle with the idle screw.

Foot note: In some cases, but not all, removing the breather tube from the air filter may result in better performance.

ps: I will gladly edit this information if I have gotten something wrong, or new information is gathered.

 

[GearNut]

No worries. I have mild lysdexia too.

 

[biknut]

Edit//after a few weeks time and further experience tuning this carb.

How to tune the CNS V2 Carb. ​

I hope you don't mind Biknut, but I have taken all the information from this thread and compiled it into what I hope will be a quick list for setting up the CNS V2 Carb. to run on the 66cc engine 1000ft above sea level or less. Further testing required for above 1000ft.

1: Raise the float level.
Turn the Carb upside down. There's a seam in roughly the center of the plastic float. adjust the float till the seam is parallel to the sealing surface of the float bowl.

2: For the high end, drill out the main jet.
Buy Machinist bits #64 #65 #66 #67 #68 #69 #70 (Stock jet size is #70)
Drill out the jet one size at a time starting with #69 Test and check for full throttle response and spark plug color. Below 1000ft altitude #65 and #64 seem to be about the right
size. If you drill to large of a hole, fill with solder and re-drill with a smaller
bit.

3: For mid range, adjust the C-Clip on the throttle pin.
(Top is lean and bottom is rich) Again check your spark plug for direction.
Black is lean, white is rich, you want a tan or brown color between.

4: low end or idle.
The air and idle screws on the side of the CNS V2 Carb are for setting the
idle fuel/air mix. First turn the air mix screw (left) all the way in and back it out 1 full turn. To raise the idle turn the idle screw (right) clockwise, counter clockwise to lower the idle. Now fine tune the air screw where your engine runs at it's highest rpm then lower the idle with the idle screw.

Foot note: In some cases, but not all, removing the breather tube from the air filter may result in better performance.

ps: I will gladly edit this information if I have gotten something wrong, or new information is gathered.

I edited this post into the first post. As more information comes out about tuning this carb, I'll try to add it to the first too.