A Carb Poll

I don't believe that the stock carb limits performance until you do much modification to the port timing. If the A/F ratio is good for your conditions, then save your money. I have a bone stock carb on an otherwise higher compression/pipe/ported/intake 66 and it is faster than my old 66 with cleaned up ports/pipe/intake/cns-carb. The old motor needed much leaner jetting than the cns carb had stock, but I cant find jets anywhere for it. The only advantage to a better carb, like a mikuni, is accurate A/F tuning across the RPM range. I run 20:1 to get my stock carb lean enough, even with the needle dropped all the way down. The CNS is much richer out of the box, and needs a smaller main jet. I'll slap it on tomorrow to see if there really is a difference.

i thaught the cns was a waste of money. my stock carb jetted has been the best so far no matter what engine work has been done..

Out of all the carbs I have tried the stock works the best

PaulFlorida said:

I don't believe that the stock carb limits performance until you do much modification to the port timing. If the A/F ratio is good for your conditions, then save your money. I have a bone stock carb on an otherwise higher compression/pipe/ported/intake 66 and it is faster than my old 66 with cleaned up ports/pipe/intake/cns-carb. The old motor needed much leaner jetting than the cns carb had stock, but I cant find jets anywhere for it. The only advantage to a better carb, like a mikuni, is accurate A/F tuning across the RPM range. I run 20:1 to get my stock carb lean enough, even with the needle dropped all the way down. The CNS is much richer out of the box, and needs a smaller main jet. I'll slap it on tomorrow to see if there really is a difference.

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Really? Odd, I found exactly the reverse to be true concerning jetting - the CNS was almost perfect "out of the box" with jus' a lil fine tuning needed with the fuel/air mix screw - heck I'm even one of them crazy folks runnin' a 100:1 synthetic lol yet I've not even touched the clip settings let alone the jets on the CNS while the old "stock" carbys are notorious for runnin' way rich... I'm assuming given yer in Florida that we're both at sea level...

This may sound dumb an' I don't mean it that way - but is there any chance at all you've mistaken which way the enrichment circuit works? I only ask because of my own foolishness - when I first installed it I had the lever the wrong way I've also noticed it's quite sensitive to air filter type & cleanliness...

I find the CNS to be a very mixed blessing overall - while I think it a far far superior carb to the ol' NTs, it's true that they require quite a bit of fiddling to get 'em "just right" - but that's the trick of it, you can get them dialed in for across the full RPM range. The "downside" is the more adjustment a carb allows for - the more adjustment yer required to do & I suspect for the vast majority of folks it's simply unnecessary complication, particularly w/o a shift kit and/or spending all yer time @ WOT *shrug*


I will say given the troubles folks new to engines have dialing in even just the simple, old style carbys w/just clip settings & jets... I'm a lil concerned that the new motors that include the CNS as stock are going to be quite problematic as the CNS is FAR more sensitive to the slightest change... while before we could simply advise "move the clip to the 2nd notch frm the top & chk plug"... with the CNS... geez, I dunno - it's so very dependent on so many variables (which is ofc part of why I like it lol)...

The only prob I ever had with the stock carb was flooding. No amount of adjusting the tangs worked for me until I gently arched the tangs. That in turn seemed to allow the float to recenter itself better. It was flooding until I did that little bit to it. I played with three carbs that year drove me crazy .

I had a friend that was the king of automotive carbs he had done tons of them as a professional mechanic. That's where I got the Idea.

That said I have had good luck with the stock carb. My China's run fine with them. For outta the box I cant complain. I will not put down the stock carb at this point.

I do want to try a carb with more adjustment though. Last a myrid of other mods porting,port timing tuned pipe etc.

Unfortunately I am saving money and hoarding parts still for my next two builds.

I have had luck with is my buddy's Dellorto, and that one was provided by a sponsor. It takes a little tuning and does have a little better performance. But I can get the same thing out of a stock carb with a little work and it dont cost so much.

For those of us at high altitude (above 5000 ft) the more adjustable the carb the better off you are. I just installed a CNS carb last week and can't be more happy with it. Yeah it took a little more time to dial it in right but was well worth it. It even motivated me to go back to my other two bikes running stock carbs and solder and re-jet for altitude and that made an improvement but still not as much as the CNS did all on it's own. Am considering re-jetting the CNS too to see if it can improve even further.

fairracing31 said:

The only carb I have had luck with is my buddy's Dellorto, and that one was provided by a sponsor. It takes a little tuning and does have a little better performance. But I can get the same thing out of a stock carb with a little work and it dont cost so much.

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This Dellorto was provided by my Buddy Alex (Blue Fox) sponsor. And not by any sponsor of Motorbicycling.com or for me.....

Baw, I was gonna say that about the new kit's. I really hope they got them things more dialed in or there are gonna be some words said i'm sure. all of a sudden the stock carbs will be the desired carb lol. maybee someday i'll devote a whole day to making a cns work for me maybee the 2 i have are duds? who knows. and at 100:1 an already rich carb would be even richer. baw you are a lucky dude to have it work great for you

amazing variances in peoples experience, even more so
nearly as many people said waste of money as who said improvement.
i got the "red" carb im sure some of you know from "bikeberry" maybe.
to be honest i would be guessing if i said i knew where, but all i have to
say is good things. still limited adjustment (c clip job) but it will let the motor
rev freely, as far as your willing to push it. it would sound like four stroking before
if you held the clutch in and revved it, now it sounds like an angry chainsaw.
im not game but my mate revs the guts out of his (same carb) and i just laugh.
lower speeds suffered a bit but the top end it gets is well worth it. i noticed the bike
sounded better as soon as i fitted it, even at idle.didnt quite sound like a nice
2 stroke before, if you know what i mean. couldnt be happier, sounds like the motor
is running the way it should have been.some people run this carb and say there was no difference.
odd.
just my 2c.

I suspect it's a simple matter as the right tool for the job, even as minor as simple expectations... advertising tends to give folks the wrong impressions...

If you're prone to riding around at WOT/redline & interested in speed alone, there's little to be gained from a more complex carburetor - wide open throttle relies solely on the proper sized main & clip settings & even the most basic carburetor would be all that's needed.

If your interested in improving the full range of RPM because you tend to put about, have a shift kit to maintain a higher speed at a lower RPM, interested in maximizing fuel efficiency and/or just want your engine to run it's very best even if just idling - that's all a more complicated carburetor provides.

Is it worth the extra fiddling and effort for no perceivable gain in top speed? That's up to you and what you want from your bike.

Aside from variances in throat sizes, there's no added advantage to be had from just a speed perspective... but maximum speed isn't the only aspect of "performance" in my book anyway

i used all the after market carbs, with the proper jetting the stocker works best for me. with a #73 jet and needle on the 2nd clip i get good performance, even with a pipe and porting.

I'm in the 'stock is better' club... A simple re-jet & moving the 'C' clip up or down can get your bike running fine!

It's also 'luck of the draw' on if you have a good engine to start with. (some engines just aren't happy no matter what carb you put on them.)

I voted 'waste of money'.