I have the Grubee Skyhawk 80cc motor. CNS carb. It runs great, starts right up, idles, climbs hills. I only have one stupid question concerning the choke. When sitting on the bike and looking at the choke there is a blue curved line that is smallest near you and gets larger as it curves away from you. NOW - when starting my motor I move the choke away from me to about half way (in warm weather) and bike starts. I then need to move the choke further away from me to get it up to speed and smooth running. Since I am moving the choke away from me I am compressing the spring on the choke inside the carb. Am I opening or closing the choke, because if I am moving the choke lever to the large end of the blue curved line I would think I am opening the choke because that is what the large end of the blue line indicates to me. Anyone understand what I am saying - OR AM I NUTS AND DO THE CHINESE HAVE THE BLUE LINE BACKWARDS?
A really dumb choke question
- Thread starter oldguy387
- Start date
Hey I was wondering the same thing. This means that my engine will only run with choke on. Why would this be?
LOOK here for your answer.
You have a dangerous air leak where the carb and manifold connect.
http://motorbicycling.com/f39/installing-carburetor-manifold-your-motorized-bicycle-303.html
Alright thanks, I'll have to go out and buy some of that sealant. For now, is it unsafe to ride my bike? It runs really strong right now on full choke, but as soon as I move it past half choke it dies immediately.
You are running LEAN too much air not enough fuel OIL mix in your engine.
It needs the OIL very badly to keep on running.
Fix it soon.
It needs the OIL very badly to keep on running.
Fix it soon.
I found the air leak, it is just behind the clamp you use to tighten the carb onto the intake manifold. How should i fix this?
Did you use the rtv or silicone sealant like the post advised ?
You may have to do it again.
http://motorbicycling.com/f39/installing-carburetor-manifold-your-motorized-bicycle-303.html
You may have to do it again.
http://motorbicycling.com/f39/installing-carburetor-manifold-your-motorized-bicycle-303.html
I don't have rtv silicone. I read in another post that you can use a rubber O-ring. Would you advise this? If so, i would rather use the O-ring than the rtv silicone, but i can just as easily get that.
I've never used the O-ring, but the O-ring relies on pressure to keep a seal. Silicone sealant works great and doesn't increase the space between the carb and the engine. I also like the silicone because it helps keep the carb in place.
If you make a copper spacer like I did you can solve all problems with the carb getting loose.
http://motorbicycling.com/f51/cns-carb-spacer-30179.html
http://motorbicycling.com/f51/cns-carb-spacer-30179.html
The "Choke" on a CNS carb has nothing to do with air, because it's not a "choke", its an "enrichment jet" that adds more gas.
I think the lever that they are using for the "choke" is just a generic old school shifter lever and the decal on it likely has nothing to do with the function of the choke specifically...
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The CNS carb is a bit different from the older NT or Speed carb. To start out it has 3 jets instead of just one, and doesnt have a real choke....
On the choke, it is not a choke, its an extra enrichment jet. When you move the lever so it pulls the "Choke" cable it lifts the plunger which opens the enrichment jet and allows fuel to flow from the jet. Pulling the cable opens the jet, creates the "choke" condition by richening the mix with extra gas.
The white spacer is just that, a spacer, it is not the seal. The spacer is there just clamp and hold the carb in place. In the throat of the carb there is a black rubber piece, THAT is the seal that stops the air leaks. It is not a simple o-ring, it is formed to fit over the end of the intake pipe and seat inside the carb throat. You need to get the carb all the way down the intake pipe and seat it into that black rubber gasket to seal the carb. You shouldnt need any sealer in my experience. Just push the carb back until it bottoms out on the intake and then wiggle it around a bit until you feel it seat that last couple of mm into the black gasket, then while firmly pressing the carb in place tighten up the screw on the neck of the carb. The screw on my CNS carb was cheap and wore down quick, I couldnt grab it very well with any screwdriver. I replaced it with a better screw (and nut) which tightens down much better for me. (it dont have to be the same size/thread screw, just get a similar size screw and nut that fits in the hole and it will work)
I had carb leaks at first before I familiarized myself with the actual carb seal, since then I use the above mounting method with the carb and never had any leaks since. I have had the carb on and off plenty of times...
If your motor will only run when there is slack in your choke cable (not pulled) then I wouldnt worry about it, that is the normal position. If you have to pull the choke cable to get her to run then you are probably running lean as suggested, since the extra gas from the enrichment jet gets things rolling.
Over the past few months I have had this CNS carb tuned so many different ways, sometimes it would idle with the choke on, sometimes not. I never had much use for the choke until the weather turned cold, then it helped smooth out my ride for the first little bit before the motor warmed up.
On the choke, it is not a choke, its an extra enrichment jet. When you move the lever so it pulls the "Choke" cable it lifts the plunger which opens the enrichment jet and allows fuel to flow from the jet. Pulling the cable opens the jet, creates the "choke" condition by richening the mix with extra gas.
The white spacer is just that, a spacer, it is not the seal. The spacer is there just clamp and hold the carb in place. In the throat of the carb there is a black rubber piece, THAT is the seal that stops the air leaks. It is not a simple o-ring, it is formed to fit over the end of the intake pipe and seat inside the carb throat. You need to get the carb all the way down the intake pipe and seat it into that black rubber gasket to seal the carb. You shouldnt need any sealer in my experience. Just push the carb back until it bottoms out on the intake and then wiggle it around a bit until you feel it seat that last couple of mm into the black gasket, then while firmly pressing the carb in place tighten up the screw on the neck of the carb. The screw on my CNS carb was cheap and wore down quick, I couldnt grab it very well with any screwdriver. I replaced it with a better screw (and nut) which tightens down much better for me. (it dont have to be the same size/thread screw, just get a similar size screw and nut that fits in the hole and it will work)
I had carb leaks at first before I familiarized myself with the actual carb seal, since then I use the above mounting method with the carb and never had any leaks since. I have had the carb on and off plenty of times...
If your motor will only run when there is slack in your choke cable (not pulled) then I wouldnt worry about it, that is the normal position. If you have to pull the choke cable to get her to run then you are probably running lean as suggested, since the extra gas from the enrichment jet gets things rolling.
Over the past few months I have had this CNS carb tuned so many different ways, sometimes it would idle with the choke on, sometimes not. I never had much use for the choke until the weather turned cold, then it helped smooth out my ride for the first little bit before the motor warmed up.
Alright i installed the O-rings. Now it runs on 1/2 to 3/4 choke and i sprayed WD-40 where the leak used to be and the rpm's didn't fluctuate, so the leak should be fixed. However, the bike runs well on 1/2 throttle, then on 3/4 it bogs a lot, and then on full throttle it runs well. Does this still mean its not getting enough fuel? P.S. I had the same bogging throttle before the O-ring was installed
Do you have to ALWAYS run with the choke at 1/2, or just to warm up? If you always need to use the choke then there is something wrong... Let us know about the choke, cause its no use messing with mid throttle adjustments before you figure out why you need to run with the choke on...
If you do indeed require the choke always to run then there are a couple things that need checking. You might need to do a float adjustment, might need to clean/ream the pilot jet, and might need to clean the main jet.
To adjust the mid throttle range (fix your bog) you would need to make a needle adjustment. I cant tell you if you are rich or lean in that range, but this test can help figure that out with the cns carb. With a warm engine not running on the choke get her up to the speed where she bogs, while bogging pull the choke on a bit, if the bogging goes away then she wants more fuel, and you need to move the e-clip toward the pointed end of the needle to richen the mid throttle mix.
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Yeah, I do need to run it on 1/2 to 3/4 choke all the time, whether or not the engine is warm. I have the stock NT carb, and i purchased a slightly larger jet from Sick Bike Parts because i thought that it might help with the problem if the engine isn't getting enough gas. Unfortunately the jet was too small to screw in to the main jet. So if i do need to make a float adjustment, what should I do? And regarding the throttle, I'm pretty sure it's running lean; because it only runs with choke so it isn't getting enough fuel.
Well, this thread started out about a CNS carb from another poster, now you are poking in about an NT carb. You would be better off looking for advise about an NT carb if that is what you have, cause the NT carb only has one jet and a real air choke, the CNS carb has 3 jets and no air choke. Totally different beast. If you have to run with the choke on always then there is something wrong, carb adjustments needed...
Oh I'm sorry for the confusion. What do you mean by air choke vs. no air choke? Because the NT carb i have has a hand choke, not the normal choke just behind the air filter.
NT carb choke restricts the air flow, it is a real choke. The CNS carb has nothing to restrict the air flow, it has an extra enrichment jet that richens the fuel mix instead of choking the air. So the "choke" on the two carbs are totally different.....
Alright, thanks for your help. I'm new to this and I can't for the life of me figure out how to post a new thread. I'd like to start a new one instead of just mooching off of this one, which is supposed to be about the CNS carb as you pointed out. How do I post a new thread?
