cns carb ! beware!!!

[rogergendron1]

so my bike started to bog a little and leak from the over flow hose and also the idle suddeny would go out off and on pluss my choke was all jacked up it was making my carb overflow and the motor run leaner when turned on !!!!! the choke is suposed to richen the mix on this carb !... ok easy fix the float bowl needs to be adjusted to close sooner so the fuel wont fill the bowl to the overflow post...thats what i thought the prob was.....

so i open up my carb and i find the float chamber filled with plastic hunks and strands all half desolved and everywhere !!! no way ! my idle jet was clogged with it and it was all over and in every passage !!!


so i clean it up and give it a warm soapy wash and blow out all the ports pasways and jets..............

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

then after the soapy was and blow out i decide i am going to inspect all the ports with a led flashlight ..... here is what i found....

the choke hole was drilled off center and strait through the casting into the top of the float bowl !!!!!!!!!!!!!!!!!!!!!!!!!!!! W T F !!!!!!!!!!!! no wonder it didnt work right !!!

so when i turned the choke on instead of drawing gas up through the tube that runs to the bottom of the bowl it sucked the air from the top of the chamber above the float giving the motor air instead of fuel !!!!! that suction of air from the choke was fed by the vent tube and caused neg preashure in the bowl causing gas to be sucked in from the float needle over flowng the bowl and leaking everwhere !!!!!!!!!


the light shining through in the first pic is from the hole the drilled throgh into the top of the float bowl !!! in the last pic i put a flashlight in the choke hole and you can see exactly where the hole in the roof of the chamber is !!!! the brass post is not even funtional because they missed the passage !!! it just pulls air from the top of the chamber over the float and it keeps getting iar fed to it by the vent tube and causes neg preasure and then suckes from the float boal needle and then floods the bowl ....

honestly i have never seen anything like this in my life WHERE IS QUALITY CONTROL ? HOW COULD THIS PASS!!!!

to fix this i have removed the choke cable and blocked off the choke with a bolt holding the spring and plug in place.

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

here is all the plastc i got out !!! just out of the carb !!!!!

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

this would have been a great carb if it wernt f ed up !!! now i have no choke ! and the only real thing to do to fix this would be to just get a real carb like a mikuni vm or a detoro no junk clones with crappy castings and misdrilled holes !!!! so i am looking at a 60$ part now, but i will run this one without the choke temporaraly until i get some cash to buy a real carb.

all those vent hoses surve no pourpose aside from sucking dirt in eather lol
i think they stuck them on there just so it would look cool to the uninformed ... average joe see's a carb with all kinds of bells and wistles and hoses and thinks wow thats must be high preformance lol but we all know a high preformance carb is nothing but a carb that meters fuel and air verry well and is very adjustabe and that is all !

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

now that this thing is together i have to readjust my air fuel mix and idle ... i hope with the choke blocked off and everything cleanned up i can get this tuned up right now !!!

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

ok got it all together and on the bike and test ran it wile tunning it ahhh damn it now it 4 strokes at all rpm's when not under load ! the air fuel mix i keep turning out 1/4 turn but its still doing it .... another few turns farther it will be all the way out and i still think it will 4 stroke,also my needle is non adjustable the clip has only one pos all the way up. should i order a few smaller main jets ? the stock one is not labled however so i do not know what size to order as i do not have a refrance point to go on lol

what size is the main jet in the cns carb on the grubee gt5 ???


on that note.... the bike even though its 4 stroking when not under load, is running a lot better and has a snappier throttle responce. it also pulls hills a little better than before. and runns a little bit faster but winds out at the top end.

 

[mrfubs]

Re: cns carb...OMFG ! beware!!!

not sure what caused the plastic to do that but as far as the 4 stroking goes its just as simple as rejetting. i believe stock is 70-72.

 

[nightcruiser]

Re: cns carb...OMFG ! beware!!!

That's pretty bad, but in general quality control is pretty bad on these motors. This isn't rocket science and they aren't manufactured by high paid skilled workers like in an auto plant, so the quality control is pretty much up to you...
If I were you I would send the pic showing light (improperly) coming through the enrichment jet area to the retailer and ask them to send you a new carb, I don't think they would have a problem with that, this is obviously bad manufacturing and not something you did to your carb.
I've had a CNS carb (V2) for a couple years and have been pretty happy with it since I got it tuned up. The float setting has a huge effect on the mix, I found I can lean it out quite a bit with the float adjustment. Mine hardly ever 4 strokes and has nice throttle response through the whole throttle range, and I do like the handle bar choke lever.... Well, not the cheap lever so much, I connected the choke cable to my unused front derailleur lever, which is real convenient. I find I just need the choke for a few seconds when I first start out so I just hold it in with my thumb (don't push it far enough to latch) and then release when she starts to smooth out after a few seconds running.
The CNS carb catches a lot of flack here in the forum, but if you get one that is manufactured properly and get it tuned properly they do work really well....

 

[stonegrinder]

Re: cns carb...OMFG ! beware!!!

The float setting has a huge effect on the mix, I found I can lean it out quite a bit with the float adjustment....

How do you properly adjust the float? I need to lean out my cns carb. The thing only runs right if I take the air filter off.

 

[nightcruiser]

Re: cns carb...OMFG ! beware!!!

How do you properly adjust the float? I need to lean out my cns carb. The thing only runs right if I take the air filter off.

Bend the tab up on the float so that it closes the needle valve earlier and keeps less fuel in the bowl...

 

[stonegrinder]

Re: cns carb...OMFG ! beware!!!

Thank you! Going to try it in the morning and see how it goes. I think I am down to the last couple things I can try. If it doesn't work by end of day I'm done with it and ordering a new carb. My wallet can't take anymore abuse that my other vehicle is giving it. That would be my '69 ford 3/4 ton with a 360ci that gets about 7 mpg. yea...ouch.

 

[Huffydavidson]

Re: cns carb...OMFG ! beware!!!

Pirate cycles said it the best CNS carburetor is an overjet ,untuneable, mystery carburetor .
Many other members here and said things like they should have jailed Don Grubee for bringing that POS into the country . BUY A RT.

 

[mrfubs]

Re: cns carb...OMFG ! beware!!!

that is not the correct way to lean out your mixture. To make dramatic increases or decreases in mixture you will have to play around with the jet sizes. In your case your going to want to go down in jet sizes in increments of 2 or until the engines quits 4 stroking at max rpm. KEEP IN MIND do not tune your engine until it is warmed up!

Also on the CNS carb there is a pilot jet that controls idle-1/2 throttle. The air/fuel screw is for the really fine adjustments(screw out to lean and screw in to richen). You want the float as high as it will fill the bowl with out over flowing out the tube. So leaning out the carb via less fuel in bowl your just not feeding the pilot jet because it sits higher in the bowl than the main jet.

1. get bike warmed up, take the bike for a 1/2 mile at least in order to get a proper plug reading.
2. take the plug out and see what it says! Make your adjustments as needed to get a nice tan burn on the insulator of the plug.


The CNS is not a bad carb like everyone says, you just need a little bit of tuning knowledge. A carb in basically any situation you cant just slap on with out tuning to get 100% results. Your elevation above sea level makes big effects on performance.


Good Luck!

 

[stonegrinder]

Re: cns carb...OMFG ! beware!!!

I tried to go that route, changing to a smaller main jet, to lean out the mix, and it had no effect. I went down as far as a .64 in .02 increment changes from the stock .70

 

[nightcruiser]

Re: cns carb...OMFG ! beware!!!

mrfubs, solid/correct theory, however, I messed with my CNS carb a lot initially and what I said about the float setting is what happens in reality. Lowering the fuel level in the bowl a bit DOES lean out the mix quite a bit and that was the magic bullet that made mine run great...
I had done some jetting (I think I ended up using a #69 or #70 drill bit to cut my jet) but the float setting still needed some adjustment to get her running sweet.

A quick and easy test, while 4-stroking turn off the fuel valve and keep riding the same speed, if the 4-stroking stops after a little bit then you can probably fix it up with a lower float setting....

 

[mrfubs]

Re: cns carb...OMFG ! beware!!!

If you keep the fuel level below the pilot jet you will suck air instead of fuel through the pilot jet, that's why its leaning out. going down in size 3 increments isn't much. I went from 70 to 94 so that how's you how much play room you have. Eventually you will get it where you want. Peace

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

wow man finaly after a week of tunning and soldering and drilling and resoldering and redrilling jets and adjusting floats and numurous plug chops at differant rps and throttle positions i fiiiiinaly have this thing tunned to the T !!!!! even without the choke i still managed to tune it pretty good. i got rid of all most all the 4 stroking .. wel i decided that i want some 4 stroking at cruise with no load, but uder even the slightest load or acseleration there is none and all is good thoughout the rpm and throttle range !

pics of stock plug from engine before i tore down the carb and tunned it and pics of the current plug after tune ! also pic of how i tunned my motor

just have to e mail them to myself from the phone

u know ... this carb if the quality were there ... would be a verry nice carb !!!! i have learned this cns carb inside out and i decided i like it, now i can easly tune it myself and i know where and when what jets come into play and how to adjust them to work together. even though the needle has no clip adjustments i have found that the air idle screw goes all the way up to almost half throttle anyway and the needle has a shorter duration than normal carbs before the main comes into play. it never realy needs to be adjusted because the air idle screw can cover most of the beginning of its range.

all in all i like the cns now ... probably only becaust i know it now and can adjust it and i bet would love a sha deltoro ! but money is tight and if i were to buy a new carb it would be a walbro !

ohh and this carb does not respond well to float bowl adjustments ! when adjusted way down it ran exactly the saame as before acsept at fll thottle for a long time it would runn out of gas by drainning the bowl, and at a high position it ran the same as before acsept when idleing it would overflow and leak out the vent hose. right in the middle and it wont run the bowl dry or overflow and seems to rn the same ... i dont thing you will get any leaning or richening out of this carb by flaot adjustments at least from my experiance.

just set it so you have a full bowl without overflow on lvl ground and you will be set. if it bogs wile at full throttle for a wile you need to raise it up to let more gas in .

 

[rogergendron1]

Re: cns carb...OMFG ! beware!!!

ok here are the pics...........
as you can see the 3 prong plug was the one that came with the motor and was used wile the carb was run stock with the recomended 16:1 ratio lol its terrible !!! AND THEY CAPPED OFF THE CARB ADJUSTMENTS SO YOU CANT CHANGE IT LOL

the single prong plug is my current plug after pulling the cap of the air idle screw and tearing the carb down and rebuilding it and cleanning out the garbage that was in it.... nice brown color.

to get it tunned i marked a line on my throtttle for idle then marked a line for wide open then half throttle then 1/4 then 3/4, this way i can see where my throttle was wile my bike was running and properly tune the correct jets