CNS Carb or NT Jets?

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Techbiker

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Oct 27, 2009
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I am debating about whether I should go with a new CNS carburetor or with a couple different jets for my old style NT carburetor. My 70cc Dax engine is running very rich and my plugs foul right away. It usually 4 strokes and only 2 strokes occasionally when I am going up a very steep hill. I also need to get an offset intake manifold since my stock one hits my seat tube. I was wondering if it would be a better idea in the long run to just get a CNS carb. I am guessing that I will spend $25-$30 on an offset intake and a couple jets including shipping while the CNS carb is $50+ shipping from Spookytooth. Will the CNS carb allow me to lean out the engine a bit and is it worth the extra $25? It also comes with new fuel line and throttle line so I would take that into account too... I am only wondering this because if I end up having to rejet the CNS carburetor anyway with a smaller jet or something, I might as well just get some jets for my old carburetor.

Thanks
 
turkman

turkman

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Nov 12, 2009
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Hey now I don't know what you should but here's what I did and what happened,44 tooth rear sprocket nt carb 29 mph,plenty of torqe on hills ,changed sprocket to 36 tooth 32-34 mph ,tried re jetting and ? didn't seem to make a diff , put on a CNS stock manifold 35 mph no four stroking , made a large id manifold 39 mph BANG!.I wonder if your motor is broke in it took about 4 gal. to get mine to smooth out that all I got on this , good luck Later Bob
 
T

Techbiker

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Oct 27, 2009
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I've put about 150 miles on the engine so it might not be broken in yet, although it does seem to be picking up more power. I guess that you recommend just getting the CNS carb. $50 isn't too much and it seems to come with quite a bit of accessories. I'm running a 40 tooth sprocket by the way.

Thanks
 
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stv1jzgte

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Feb 11, 2009
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Firstly if you are 4 strokeing with an nt yes your way to rich and should fix that first and see how it goes
. Bolting on the cns will cause it to constantly 4 stroke as the jet is alot bigger than the nt yeh it process more air but more fuel also.

Rejet you nt smaller you should never be 4 stroking

You can just but a smaller drill bit, solder your jet up then drill smaller .60 - .65 should do it
 
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421SmQQthie

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Feb 6, 2010
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i just ordered a cns carb for mine because the old style carbs are designed for a 49cc motor and never should have been sold for 66cc or 80cc the cns carb has a bigger everything but yea mabee your not mixing your gas proper is it is 4 stroking the only reason i ordered my carb is because at top rpm's the motor seems to be running out of gas or hitting a govner i think this new one will help[ but i will know soon just ordeered it tonight.
 
T

Techbiker

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Oct 27, 2009
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I talked with Spookytooth and they just recommended going with the CNS carb since it includes a fuel/air mixture screw and since it is more precise. They said that the fuel/air mixture should work with a stock 70cc engine but that it will need to be adjusted. I'm going to install the new carburetor this weekend so I will get back and let you guys know what happens. Hopefully I'll be able to get the mixture right.

Also, I plan to grind out my muffler opening to improve air flow. I don't want to grind out the inlet/ outlet on the cylinder right now since I don't want to take the engine apart. Hopefully this will allow the engine to run better. Thanks for the replies.

Does anyone have any experience with adjusting the CNS carburetor?
 
bairdco

bairdco

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Aug 18, 2009
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before you start spending money, have you tried the basics? like moving the needle clip up? what mixture are you running? you say you've got 150 miles on the engine, have you leaned out your mixture or are you still running the same fuel/oil ratio as your first tank? is your air filter clogged with oil? have you smoothed out the casting flash in the intake manifold? you can do a little port matching to it with a dremel, too.

there's a lot of little basic things that you can do for free before you start throwing money at your problems.

i'd hate to read a thread from you saying how the new carb sucks and it's a waste of money...
 
Venice Motor Bikes

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Yep... I've had really good luck with simply jetting & cleaning up the stock carbs!
I can't believe how many times I've read about guys who put every high $$$ part they can find on their bike, & then they can't get it to run right!?!?! :rolleyes:
 
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stv1jzgte

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flybytaco said:
exactly baird no pissin match here man but yes i do think the nt is the best for the ht i have 2 cns carbs and they are both in boxes not on bikes all because they were to big yes video doesnt lie and i was disapointed with the cns bigtime if your going to spend money buy the delorto been hearing good things
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No ive had no problem tuning the cns seems to work much better for me than the nt ever did though
40-50mile an hour out of an nt is downright amazing.
I think its great there are some videos out there but it would be good to see a vid of a gps straped to a bike.
 
BarelyAWake

BarelyAWake

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Jul 21, 2009
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While which carb is better is a never ending debate lol - there's defo some truth in wonderin' if a more complected carby isn't just gonna cause probs for someone havin' trouble adjusting the dead-simple stock one.

Still - if you've gone through the process, know yer carbs and wanna try bringin' it to the next level - there's nothin' wrong with kickin' out for a quality carb with more features and chuckin' the stock one in the ocean... where in my personal opinion - it belongs :D
 
T

Techbiker

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Oct 27, 2009
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I moved my c-clip to the second highest position (2nd leanest) from the middle position and it didn't seem to change anything. I'm completely prepared to tune the new carb as I like tuning everything I have for maximum performance (like computer, car, etc.). I really want to learn how to tune a carburetor and the stock one is simply too basic. I suppose that if I have to I can always rejet the CNS carburetor. $50 was a pretty good price considering that I would spend about $25 adjusting my stock carb. I'll report back once I've done some dremmeling and have gotten the new carb on and adjusted. Thanks again.
 
bairdco

bairdco

a guy who makes cool bikes
Aug 18, 2009
6,537
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living the dream in southern california
i love the NT carb. i've never re-jetted, i just grind the little step on the intake side of the bore, polish it all up inside, match and clean up the intake manifold, and haven't had any problems whatsoever.

eventually, i'll get a Dellorto or a Mikuni, just because i wanna have something new to play with.

but what i'm trying to say, is, before you spend money on a carb to fix your problem, make sure it's actually the carb.

the bike i'm putting together now, i just slapped a stock intake on it, and it 4stroked all over the place. i ported it, cleaned up the carb, made a custom copper air filter, and it's super smooth, responsive, and, well, it's good.

and it cost me nothin' but time.
 
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stv1jzgte

New Member
Feb 11, 2009
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Techbiker said:
I moved my c-clip to the second highest position (2nd leanest) from the middle position and it didn't seem to change anything. I'm completely prepared to tune the new carb as I like tuning everything I have for maximum performance (like computer, car, etc.). I really want to learn how to tune a carburetor and the stock one is simply too basic. I suppose that if I have to I can always rejet the CNS carburetor. $50 was a pretty good price considering that I would spend about $25 adjusting my stock carb. I'll report back once I've done some dremmeling and have gotten the new carb on and adjusted. Thanks again.
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Tech by moving the c clip all that really does is adjust your part throttle, If you want to tune everything for maximum performance Re drill the jet smaller forget about drilling it bigger as suggested your to rich allready as i said in post 4. Cost of about $2.50 thats it.
If you use the cns carb you will have to rejet smaller as it is about .80 and you will 4 stroke regardless of the c clip setting.
 
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