yet another CNS carb that doesnt work

pocdragon · Oct 9, 2011

hello all

im in this part of the forum to help trouble shoot my carb problems

my cns carb was brand new with my gt5 kit i bolted it up and tryed it with gas before opening it up to check for shavings and debris

it kinda worked on the first pop start then died off

so months later i clear the cobwebs off my bike and try again

i completly took the carb apart and swabbed out everything

i melted the plastic off a bread tie and poked ever tiny hole i could find to clear things out

there wasnt any shavings in my carb, and there wasnt anything gumming up parts

the float and needle both work well

i epoxied the carb to the manifold to ensure there are no leaks to the head

the set screws were a turn an a half out from tight

i didnt seal any hoses off i left them all stock and i didnt drill out any jets

what can i do to trouble shoot the carb im at a loss
:-||

thanks
all

i bolted it back up and tryed it out and

decoherence · Oct 9, 2011

did you get it started?
if you couldn't that is one direction.
if it @ least fired off a couple revolutions that could be another thing.

pocdragon · Oct 9, 2011

yes it will kick over and continue to run @ WOT and full choke , if its in ggear it only goes like 12mph

if i let off the throttle it will back off the revs and die

when you let the choke out it doesnt sound any different untill you let off the throttle, and if you let the trottle return all the way it would idle nice and quietly before it sputters to a halt

also the c clip is on the third slot in the middle

any other questions i will be glad to answer to throughly analize what its issues are

thanks

nightcruiser · Oct 9, 2011

You didnt describe to use what problems the motor is exhibiting???
In my experience with the CNS carb, the small pilot jet can cause a lot of idle and low speed issues. It is located down inside that column so you cant really see it. There is a screw slot in it, if you get a flat blade screwdriver down there it should come out. Reem it with your twist tie wire....
The CNS carb is picky about air flow, if the filter gets oily it will effect the way it runs. If there is too much or too little air it will run poorly.
I dont know about epoxying the carb to the intake, that seems kinda extreme, and I pull my carb off a bit often... The rubber seal at the end of the CNS carb seals well enough when properly install in my experience.
Let us know what your symptoms your motor exhibit and we can try to help you.....

nightcruiser · Oct 9, 2011

pocdragon said:
yes it will kick over and continue to run @ WOT and full choke , if its in ggear it only goes like 12mph

if i let off the throttle it will back off the revs and die

when you let the choke out it doesnt sound any different untill you let off the throttle, and if you let the trottle return all the way it would idle nice and quietly before it sputters to a halt

also the c clip is on the third slot in the middle

any other questions i will be glad to answer to throughly analize what its issues are

thanks

CNS carb is hard to tune, I think maybe you have a lot of the issues I had with mine at first. When I first got her running I need to balls out on the throttle and she would go, anything less and she would die... Never could idle etc. I could go into what I did to mine to make it work, started with the float.... Instead I will just link you to the thread I posted about all I did at the time, I think you should find it a good read.....

http://motorbicycling.com/f4/cns-carb-working-great-32736.html

pocdragon · Oct 13, 2011

nightcruiser said:
CNS\. Instead I will just link you to the thread I posted about all I did at the time, I think you should find it a good read.....

http://motorbicycling.com/f4/cns-carb-working-great-32736.html

if u would chek out page 2 i already have contributed and throughly read your writeup

my bike will also only go at WOT
if i try to let it idle it wil just slow down rpm till it stalls, reguardless of the set screw all the way in for idle

nightcruiser said:
CNS\.
the small pilot jet can cause a lot of idle and low speed issues. It is located down inside that column so you cant really see it. There is a screw slot in it, if you get a flat blade screwdriver down there it should come out. Reem it with your twist tie wire

yup did that before when i said i went through every hole i could find

there werent any shavings like alot of others online claimed

the kill switch does not exist because id rather tune it knowing that the kill isnt the problem

if i hold the throttle at a certaing spot it will stay running and at the lowest rpm without dieing, wich is defalot higher than idle
i started adjusting the air/fuel screw at that rpm, and it didnt sound any different or smoke more or less from the air fuel

the choke on it(which i realize isnt really a choke at all) doesnt seem to do much,

can i add a physical choke on it like a weeed wacker style one with a smaller hole in it?

im going to richen up the fuel pin to the lowest clip set and if that doesnt let this thing idle im going to buy a stock motobike carb i already know how to make those work well :-||

pocdragon · Oct 13, 2011

pic for click

nightcruiser · Oct 13, 2011

pocdragon said:
pic for click

did you ever do a float adjustment??? What have you tried other than cleaning and reeming through the jets? (I want to make SURE you didnt miss the pilot jet which is harder to notice than the main jet)
I have been helping quite a few people with different scenarios, hard to keep things straight, I have to just read the latest post and comment and try to help that way.
Looking at your pic it seems your carb tilts a little forward, like mine did. I had to do a float adjustment to lower the fuel level in the bowl to compensate for that tilt before my bike ran well. Before that it was WOT or dead, idle screw all the way in and still no idle, or barely... so, did you try any float adjustments?

pocdragon · Oct 13, 2011

i unscrewed both jets and cleaned them both, yes

i didnt bend any parts of the float to adjust the action, the needle releases and seats well (maybe too well?)

its raining here in newengland
so test runs will have to wait

nightcruiser · Oct 13, 2011

pocdragon said:
i unscrewed both jets and cleaned them both, yes

i didn't bend any parts of the float to adjust the action, the needle releases and seats well (maybe too well?)

its raining here in newengland
so test runs will have to wait

You probably need to adjust the float man, tuning a carb is not just cleaning.... Just because the float releases and seats well is no reason not to adjust it, you adjust it to change the fuel level in the carb bowl, not to make it seat better or whatever... From your pic it seems your carb leans forward, leaning forward makes fuel rise higher on the motor side of the carb than the air filter side, adjusting the float to lower the fuel level can compensate for this leaning carb... Lower the fuel level in your bowl and you will probably get rid of this over wet situation in your motor.

PS Rainy days are for wrenching, sunny days for riding. Wrench today so you can ride on the sunny day instead of wrench!

IreBo · Oct 18, 2011

pocdragon said:
i unscrewed both jets and cleaned them both, yes

i didnt bend any parts of the float to adjust the action, the needle releases and seats well (maybe too well?)

its raining here in newengland
so test runs will have to wait

I agree! just cleaning is not the only thing to do, but is important.
the float level controls the amount of fuel in the bowl and if the level is too high then fuel will seep out of vents and circuits and cause a flooding scenario.

the cns carb has to be re jetted no matter what you do or think. they seem to have been set lean stock for 49cc engines not our 66/80cc engines. you need to buy a jewelers drill bit set and ream the main jet to 67 or 64. the stock is about a 70. the smaller the number the bigger. somewhere in that range seems to work great at about 1000 feet above sea level. if you have put an expansion chamber on the bike may need to go bigger. if you are higher than that you my need to adjust

since i have re jetted i rarely have to use my enricher (choke) unless it is cold out or haven’t rode for a while. i eliminated the choke leaver all together and made a small hand activated pull tab on the choke. cleans up the handle bars a bit too. less cables and junk!

the problem you have now is that you epoxeyed the carb to the intake!! DOH!! not nessary foo! you need to take it off sometimes!

nightcruiser · Oct 18, 2011

IreBo said:
I agree! just cleaning is not the only thing to do, but is important.
the float level controls the amount of fuel in the bowl and if the level is too high then fuel will seep out of vents and circuits and cause a flooding scenario.

the cns carb has to be re jetted no matter what you do or think. they seem to have been set lean stock for 49cc engines not our 66/80cc engines. you need to buy a jewelers drill bit set and ream the main jet to 67 or 64. the stock is about a 70. the smaller the number the bigger. somewhere in that range seems to work great at about 1000 feet above sea level. if you have put an expansion chamber on the bike may need to go bigger. if you are higher than that you my need to adjust

since i have re jetted i rarely have to use my enricher (choke) unless it is cold out or haven’t rode for a while. i eliminated the choke leaver all together and made a small hand activated pull tab on the choke. cleans up the handle bars a bit too. less cables and junk!

the problem you have now is that you epoxeyed the carb to the intake!! DOH!! not nessary foo! you need to take it off sometimes!

Yep, you're right about all that...
However, I found my stock jet would only let a #72 drill bit through, opened up to a #69 bit with the stock air filter and she ran great. When I opened her up further to #65 I lost about 7-10 MPH off the top end, until I opened up the air filter for a little more flow, then the top end came back.
Riding weather here is pretty much gone now, but next season I plan to install an aftermarket air filter and retune this jet. I also have a rebuild kit, the main jet in THIS kit was the size of a #70 drill bit (unlike what came with my kit). After tuning with the aftermarket air filter and riding a while I plan on installing the stock rebuild kit along with the stock air filter, just to get a comparison. I want to try this because I was super happy with the way the bike ran with the #69 hole and stock filter. Sucks I have to wait until next spring to mess with this more...

decoherence · Oct 18, 2011

now that i finally got a job i can pick up some drill bits. or jets.
is it the main jet or the idle jet that needs work?

nightcruiser · Oct 18, 2011

decoherence said:
now that i finally got a job i can pick up some drill bits. or jets.
is it the main jet or the idle jet that needs work?

You just need to make sure the idle jet is clean, it's the main jet that you would be opening up.
A set of drill bits only costs about $6 bucks delivered from ebay....
New 21pc Mini Micro-Drill Bits Set Index 61-80 w/ Aluminum Hand Drill | eBay
That set covers sizes from #61 to #80, perfect range to jet your CNS carb. Be careful to pull only one bit out at a time, and don't bump the case and get all the bits loose, since the size increment is so small it is next to impossible to tell them apart....

decoherence · Oct 18, 2011

i am going to pick up drill bits from a locally owned family hardware store.
i have never done business w/ebay & never will if possible.
i don't do business with companies that i don't like their business practices.

my jets are clean. i have removed & soldered the tube that goes into the front.
here is the thread i started & will continue when i progress more.
http://motorbicycling.com/f51/you-can-polish-turd-project-33449.html

here it is before i started polishing.

it is now in between polished & brushed inside & out.
more like a satin finish.

nightcruiser · Oct 18, 2011

decoherence said:
i am going to pick up drill bits from a locally owned family hardware store.
i have removed & soldered the tube that goes into the front.

You still have a locally owned family hardware store in your area? Good for you, all we got is big box chains. I have had great luck with ebay, if you read feedback you can tell if they do honorable business or not, but to each his own....

On the tube you soldered up, which tube? The one that goes from the top of the bowl to the air filter? My bike runs like crap with that tube disconnected or plugged, so that may have been a bad move if that's what you did.
I know others have said pulling that tube is like a magic bullet, but when I pull that tube I lose about 7-10MPH and she runs like crap. Just speaking from my experience with a Grubee 2010 GT5 66cc.

nightcruiser · Oct 18, 2011

decoherence said:
QUOTE]

Does the carb have a label on it? I am wondering what version CNS carb you have there, cause from the picture I think it is a bit different from mine.
The label on mine says C-32CNS66-EPA and I think it is the most recent version of the CNS carb.

decoherence · Oct 19, 2011

nightcruiser said:
You still have a locally owned family hardware store in your area? Good for you, all we got is big box chains. I have had great luck with ebay, if you read feedback you can tell if they do honorable business or not, but to each his own....

On the tube you soldered up, which tube? The one that goes from the top of the bowl to the air filter? My bike runs like crap with that tube disconnected or plugged, so that may have been a bad move if that's what you did.
I know others have said pulling that tube is like a magic bullet, but when I pull that tube I lose about 7-10MPH and she runs like crap. Just speaking from my experience with a Grubee 2010 GT5 66cc.

we have several. family owned stores.
if you can't find a family owned one look for a true value or service star.
they are usually locally owned.

if you look @ the pic. see that rough spot inside. that is the tube i removed.
it is now smooth
i will be taking the tube from the bottom & have a tube higher than the float line & either have it vent to the open.
also i have a harley sportster tank & besides the vented cap it has a vent tube that sticks out the bottom of the tank that goes to the top of the inside of the tank. i might hook it to that & the other vents.
i have read that many people have had it better running from unhooking that tube from the front & letting it just vent.

i believe it is a cns v1. it is my spare so it is an experiment.
it use to four stroke a lot & the enrichment circuit didn't help starting the engine.
so if i can get it running well, i will see if the enrichment circuit will help then.
if it doesn't i will be grinding & soldering that off also.
i love dremeling & soldering so i won't be bothered if it doesn't work.
if it does work, i may let people send me their cns's to work on.
or coerce i would only be able to guesstimate their needed jets.

nightcruiser · Oct 19, 2011

decoherence said:
i will see if the enrichment circuit will help then.
if it doesn't i will be grinding & soldering that off also.
i love dremeling & soldering so i won't be bothered if it doesn't work.

The enrichment circuit on my CNS carb definitely helps in cold weather for the first bit of the run...

decoherence · Oct 19, 2011

it never did anything for me.
i also have the "speed" carb. it runs well but its choke doesn't do anything to help either.
if i can get the enrichment circuit working on the cns, i will shorten the cable & mount it any where else that isn't the handle bars.

yet another CNS carb that doesnt work

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