Air leak?

T-lo · Mar 30, 2012

new V2 carb

Man! sorry to be back in the troubleshooting section so soon. well i'll catch you up. i had a problem with fouling out plugs and leaned it up. that worked out well untill my New style CNS car broke off the air intake. so i ordered a CNS V2 carb that i had good luck with on my last bike.

Ok now i've got my new carb. but i'm not going anywhere. Engine is idleing like crazy and sputtering like it's running to rich. when i try to ride any throtle is too much and bogs down. I took the air filter off. on idle, if i give it a little gas, it's going crazy! if i lower the RPM a little it dies. When it ran right, (or close to it) i could give it some gas and choke it up a notch or two without it stalling. Now, if i click the choke up just once - stalls instantly. I'm spraying starter fluid all over the place and not getting anything. Engine is getting hot quick. I've checked head gasket, removed the head, cylinder looks fine, changed plug - nothing, checked exaust gasket, air intake gasket, and ofcorse i'm doing my best to keep the carb sealed to the intake tube. oh yea, "66/80cc" 2011 skyhawk gt5 w/ cns v2 carb, - the one with the red filter cover.

T-lo · Mar 30, 2012

i'm gona need some help with this one guys. Also to note, i've adjusted the needle all up and down - no change. just curious but.. is there any chance of messing up the timing by removing the head cylinder? i've been working on this since first thing yesterday morning.

T-lo · Mar 30, 2012

I think what i'm trying to get at is that this is an engine that is idleing high at a very narrow range of rpm - high. When riding - it bogs down when giving it any gas at all. any choke whatsoever will kill it. Other than that, you can assume that the engine was not found in the trash and was, up untill gettting the new carb and inspecting the head, a good running engine. Is this problem common of an air leak? Is there a way to tell if the leak is going into or out of the engine?

Bikeguy Joe · Mar 30, 2012

Sounds like a very lean condition...maybe an air leak. The "air leak" is actually a "vacuum leak". If spraying anything around the intake and carb made no difference, then I am guessing the seals or at least on seal is bad.

T-lo · Mar 30, 2012

ok. i'm seeing that with everything that i've checked, i've still things i haven't been able to explain a few things.
#1 lots of smoke from exaust. normally this goes away when i'm warmed up. i'm using the same gas with a 16 :1 (i think) mix.
#2 i'm getting a lot of poping noise in the exhaust like it did when i was running way too rich.
#3 the handlebar mounted choke has some slack in the line but if i click it 1 click, it will stall the engine. looking inside the carb i don't even see the plug move when i click it only once. about 4 clicks is open
#4 lots of vibration on idle.
#5 still no power if i try to ride. any throtle will kill it. messed with the choke while pedaling and even worse still.

Is this an air leak at all? i would like to try the old carb but it broke off and i can't put it back on. I tried the starter fluid, i've also tried pouring water all over the engine and where the carb meets the intake with no reaction! - except for some hot water. i'm lost.

biknut · Mar 30, 2012

First think you need to do is go to 24:1 mix. 16:1 is too much oil.

What size main jet came in it?

The cns carbs are finicky, and need a lot tuning to get right. Take a look at this thread to see what you're in for. One major advantage you have is, when I wrote this thread there weren't any jets available, so I had to drill the jet to make changes. Now you can just buy different size jets. The ones you need are the M6 size. Try a 68 first.

http://motorbicycling.com/showthread.php?t=30169

If you don't want to go to all this trouble buy a NT, or Speed carb, that's a lot easier to tune.

Good luck.

T-lo · Mar 31, 2012

i noticed that this needle is a bit wider than the last. i think this means that the jet would be too. i'm going to switch out both and update after.

T-lo · Mar 31, 2012

ok. i've noticed a slight improvement. the jet is actually smaller in the new carb with the bigger needle. i kept the needle and switched the jet. I'm thinking it's somehting to do with the choke and giving it too much gas. but the choke is not engaged. Is there a way to stop it up compleatly? plug it or something? if you could, would it still work?

rustycase · Mar 31, 2012

Yes.

I have removed my choke cable from the motor bike.
(just cuz I don't like the look of cables and wanted to eliminate one)

You must leave the plunger down in the well for the enrichening circuit, AND the spring that holds it down against the seat.

SO, with no rich fuel mixture available, it will require a bit more pedaling to start, when cold. However, you have eliminated a potential problem. IMO

Mine starts EZ enough, with the throttle closed, and barely coming off idle, when I'm starting it. I gotta take it easy for a few hundred feet when it's cold. Any other time, it's off to the races from the first bump.

Gosh, U shoulda got an NT to replace that cns... sry to say so.
They are cheap, and EZ.

Best
rc

the only reason I still have mine is probably a flaw in my nature.
It aggravates the heck out of me and I fuss with it constantly.
Sometimes I'm able to improve it's performance, but it usually falls off, for some reason or other.

.

T-lo · Mar 31, 2012

update: i tried pluging the choke. didn't help.
stuffed the hole with paper towel. didn't help.
called the place i ordered it from, they said to unplug the black hose that goes into the air filter. Didn't help.
GRRRR!
I duct-taped my old carb with the unbroken parts back on there and removed the new v2 carb. i got it started! i even drove down the road. not the best it's ran being that the plug is covered in oil, i have a new sproket to adjust and the carb was held on with duct tape! but all the problems i've been talking about have been in the carb this whole time. I'm going to say it's defective. i know theyr'e going to say it's not. i may still have to buy an NT.

T-lo · Apr 3, 2012

new V2 carb

so this is the best i've had it running so far. still not right. the sound in the video sux but if you can hear, when i give it some gas and let off, it sounds like it's going to die. it will rev ok, but when letting off it sounds like it's not firing. it's also idleing errratically. up and down all on it's own.

I still have the problem of it bogging down all the way if i give it any gas while riding. kinda like this sound. the air screw is not making any difference unless i tighten it all the way and it gets no air and stalls. if i adjust the idle screw down at all, it stalls. i've plugged the choke and that didn't change anything.

Remember, i did put my broken V3 carb on for a test and it ran fine. Problem is in the carb. but what else can i do?

http://youtu.be/fo1Lz2NrcRo

T-lo · Apr 4, 2012

This is not working. Ok.
I know that it's running way too lean. Plug is turning white. with erratic idle.
I got it to get me to go foward but slowly. any thotle will bogg and on idle, engine is running very lean punctuated by a non-rhythmic "PoP"ing sound from the exahust. The POPing was something i also heard a lot when i had the engine running too rich when i used my last V3 carb.

Let's make sure i got this down.
1. when the pin is pointing down, the notch at the top is lean and the bottom is richer.
it's not helping.
2. the float can be adjusted for how far down in the bowl it falls, regulating the flow of gas into the bowl.
3. the screw on the left is the air/fuel ratio. the tighter the screw, the less air.
4. the screw on the right is the idle rpm adjustment.
5. the jet sucks in fuel at higher rpms. the bigger the jet, the more fuel at WOT.
6. the choke, when engaged, will block some air from entering the engine causing more fuel to enter instead.

Is this about right? because when i had the clip at the top of the pin, the plug was covered in oil. i moved it down and it's turning white. now i've moved it back up and it's still turning white. What's up with that?

Bikeguy Joe · Apr 7, 2012

Have you checked the engine for air leaks?

T-lo · Apr 7, 2012

i only know that i can remove the spark plug and try to turn the engine, and put my thumb on the spark plug hole and try to turn the engine. i've done that, and it seem i do have good compression.

I'm putting my broken carb on and it rides, but it won't stay in place.

the next thing i'm going to try is putting the air filter back on. i wonder if i've been letting it get too much air with it off. My thinking was, 'if it will run with air filter, it will run better without.'

vachon644 · Apr 7, 2012

Removing intake filter leans out the mixture which in your case is not what you're trying to achieve.

T-lo · Apr 9, 2012

i put the air filter back on and adjusted the float some more.
double checking the jet - it's not a smaller jet, THERE'S SOMETING STUCK INSIDE.
i put my lips to it and blew it out of there. - gross
i'm running much better now, but still don't have much top end. I'm thinking about getting some micro drill bits for a rejet.

Do you know if they are too small for my drimmel tool?

rustycase · Apr 10, 2012

Sounds like you got a fine collection of crud from your chinagirl tank, T...
You ARE running a filter, right?

...actually, a dremel tool has too much power for the tiny number drill bits.

I solder my jets closed and redrill 'em using a pin vise. They are only three or four bucks and are just dandy for this kinda project.

We HAD a place here in town that sold the bits individually.
When I discovered they only wanted a buck and a half for em I got 1/2 dozen at a time. Probably all you're gonna need is 65 thru 75, for these chinagirls.

Good luck
rc

blazingoutcast · Apr 10, 2012

T-lo i had the same issue's as u til i switched carbs i went from cns v.3 to a speed both had the same issues the speed was better then the v.3 just cuz it would actually idle but not really drive so i switched to an nt carb since then i let her warm up n can get her to go close to 35mph once i finish this tank of 20:1 ima switch to 30:1 or 32:1 hopefully that might increase my speed but u might have n air leak so do a wd-40 test see if u cant find a leak

Rocksolidperson · Apr 11, 2012

go out of your way to get a dellorto or a clone, most reliable carb ever and has never let me down look in the link on my sig.

T-lo · Apr 21, 2012

I bent my float all crazy like and it was a lot closer to what i was looking for. a few more to the float and needle... closer still. i put a big ol' hole in the jet and not quite right untill i drilled some big grooves into the airfliter cover. i'm still running too rich, but i'm a lot better off. i can actually ride it now. Nightcrusier's post was pretty helpfull too. http://motorbicycling.com/showthread.php?t=32736

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