NT carb bogs

J

jmperry55

New Member
I replaced red CNS carb on Grubee 48cc with NT carb from BGF. It cranked OK, ran a little rough till I adjusted the choke. I ran it easy till it warmed up a little. Then off choke, ran good. But then if you accelerate too fast, it bogs down. It will run good and steady at about 3/4 throttle, but more than this and it bogs down. Also some occasional missing and what sounded like a backfire or two. Adjusted idle easily, but there are no other adjustments on this carb. Built one other 49cc that came with slightly different NT carb, and it just ran great from the git-go. I have no idea what to try. Can anyone help? Thanks.
 
Billet intakes work great-

you don't have an offset intake from the CNS do you- the NT carbs like to be close to the motor- may have other problems-- ^^ speed carbs work good too

what was wroing with the CNS?
 
Don't know what a billet intake is. The intake looks the same as came with first NT carb. The way I mounted the engine on the frame this time may make the carb a little less level if that can be of any importance.
The CNS wouldn't idle though I tried all the fixes I saw here.
 
Have you tried raising/lowering the 'C' clip on the needle? Without seeing you spark plug's color or hearing your problem I can't tell if you're running lean or rich. Rich would be my guess so in that case try raising the 'C' clip to the next notch up and see what happens.
Aftermarket so-called performance parts (billet intake manifolds) will not solve a rich/lean condition. You should be able to tune that carburetor without buying parts.

Just noticed that you're at sea level. In that case you might be a little lean. If raising the clip doesn't help or makes the problem worse try lowering it. You have more air at sea level that some of us so you might need a litttle more fuel.
Tom
 
Follow 2 doors advise but try this also.It sounds like your lean or running out of fuel. Make sure you have no air leaks. I would check the float level and make sure everything is clean inside the carb also make sure your petcock is allowing for good fuel flow. Another thing to try is an NGK spark plug if you don't have one already. I've had spark plugs do funny things like that in the past.
 
I agree with checking for air leaks. I recently had a similar problem that an air leak turned out to be the cause of. I also agree that you may need more air at sea level. NGK plugs a good idea too. Also, check your idle adjustment. I once adjusted my idle screw wrong before embarking on a 60 mile journey. The engine bogged the entire time, as if the carb was flooding, until I figured out what was wrong. I was almost home by that time.
 
Thanks to all who replied. I considered all suggestions. Plug color was dark brown. Unusual 3-prong plug. I moved the C-clip on the needle all the way as close to the end as possible and got the best performance which is as good as the first one I did. Also I seemed to notice that the more I run the engine the better it seems to get. Intake was actually shorter than the first one. This one continues to be a little harder to cold-start than the first one, but after warm-up is fine. Again, I really appreciate all your help. I just had no idea what to do next.
 
well this is the same prob I had, everytime I would accelerate it would bog bad.
It was starving for gas, I changed the main jet to a bigger one and it took care of the bog.

try this
going down the road riding it, accelerate and when it starts bogging slightly choke it maybe one click give or take. If the bogging goes away then you need to put bigger jet in it.
 
mines opposite....sealevel....c clip in top slot....lowered float level about 3/16"....stopped the 4 stroking...stopped the bog...runs 31mph...like a chain saw...rpms just keep climbing....I'm stoked.

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dance1
 
From what I have read from some of the guys here that know the nt well, it is jeted for the 66cc so moving the clip to the top leaned the mixture. How does it run at wot?
 
I am still very new at this, just got mine going....it is a 66/80cc...after following some advice on a clutch adjustment. But is seems to be missing quite a bit. I was reading the things written before, but where is the c clip you were all talking about. And my choke is an up/down slide (with lovely Chinese inscriptions) so which position is for starting cold, and which is for running after it's warmed up? I am definitely enjoying reading all of this, partly because I like to learn and partly because I have wanted to get one of these kits for probably at least 10 years so I am really enjoying it now. Using it to go back and forth to the church, about 7-8 miles each way.
 
Here are some pics I took when responding to the advice received here, that show the internal parts of the throttle, including the needle, and a close shot of the "C" ring on the needle in the second from the top slot of four slots.
 

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to Cloud...I'm new at this. I've built two bike so far. The fist bike was w/ the old style carb and it works fine however the second bike I built was w/ the new CNS carb and mine also bogs out when you give it gas. You stated that you put a bigger jet in it. Where is the jet? Sorry, kinda new at this.

Roger

Ok, after moving the c clip up to 2nd position and sealing up intake w/ electrical tape it is still spitting and sputtering and choking out at half throttle. Man, this is kickin my ass. I'm thinking calling kingsmotors today and telling them they should replace this carb.
 
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after reading all the postings so far on this topic. Today I'm going to back the c-clip off so it runs lean. Gonna try using electrical tape to seal the intake and level the carb. I'll let you all know the results.

Roger
 
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