Need help understanding CNS carb....

N

nightcruiser

New Member
My engine is starting to get broke in now and I am just about done with my first gallon of regular mix (32:1), so its time for me to start tuning the carb....
I have the CNS carb (newest version) and it is very frustrating to work with for me, I just don't seem to understand what is going on. Depending on how things are set sometimes the choke makes the engine run faster when its out, and with other settings its just the opposite, it will run slower when its out! Very confusing!
So I am wondering if anyone can explain this "choke" circuit to me? I understand that it is an extra "pilot jet" to richen the mixture rather than an air damper from what I have read. I am wondering if this choke jet is putting in extra fuel when the choke cable is pulled or when the cable is slack? I ask the question in this manner (cable pulled or cable slack) because when I read "engaged" or "disengaged" it is not clear to me (engaged=cable pullled???) At any rate, is this choke jet adding fuel when the choke cable is pulled or slack???
I think I need to understand that first, before I go any further. An additional comments or tips for tuning a CNS carb are grately appreciated..
Thanks
 
I got a cns48 that uses a cable connected enrichener circuit.
It pulls up a brass plunger on the port side of the carby that is otherwise held down by coil spring pressure.

I don't trust it to seal well enough... there's a rubber pad on the bottom of it.
And I don't trust a cable that may pull up the slack at any time with a turning movement.

I dumped the cable partly to clear up some of the clutter on the handlebars.
Gotta have a throttle and front/rear brakes, and the clutch.

I used a short piece of copper wire with a ball rolled on the end of it that fits into the brass plunger. I pull it up for a second or so when pedaling from cold and it sucks in a shot of raw gas to improve cold running... abt 600-800ft cold running I'm ready to give it some decent throttle and go somewhere.

...suppose I should put a 3" bit of loose cable on it to a lever there on the top bar, but I'm about to plug that circuit in the cns carby to eliminate that potential problem in my quest to get a cns to run right.

...and I've read through nearly all the cns threads here to find someone with a positive answer and details for making them work right... no joy.

Seems the conventional wisdom fix is an nt carby!

I hope to track down a used dellorto so life doesn't become too ez.

Good luck
rc
 
rustycase said:
I got a cns48 that uses a cable connected enrichener circuit.
It pulls up a brass plunger on the port side of the carby that is otherwise held down by coil spring pressure.

I don't trust it to seal well enough... there's a rubber pad on the bottom of it.
And I don't trust a cable that may pull up the slack at any time with a turning movement.

I dumped the cable partly to clear up some of the clutter on the handlebars.
Gotta have a throttle and front/rear brakes, and the clutch.

I used a short piece of copper wire with a ball rolled on the end of it that fits into the brass plunger. I pull it up for a second or so when pedaling from cold and it sucks in a shot of raw gas to improve cold running... abt 600-800ft cold running I'm ready to give it some decent throttle and go somewhere.

...suppose I should put a 3" bit of loose cable on it to a lever there on the top bar, but I'm about to plug that circuit in the cns carby to eliminate that potential problem in my quest to get a cns to run right.

...and I've read through nearly all the cns threads here to find someone with a positive answer and details for making them work right... no joy.

Seems the conventional wisdom fix is an nt carby!

I hope to track down a used dellorto so life doesn't become too ez.

Good luck
rc
Click to expand...

I was poking around with the cns carb, blew down the hole where the choke plunger goes and could feel air coming out a hole in the air filter side and also the hole right where the seal is for the intake. So it seems this plunger is opening an air passage for sure, and I guess a fuel jet also?
I have made some adjustments in the float, the float position seems to have a huge effect over how this enrichment circuit operates. I am not really sure how to get the "proper" float adjustement, my carb sits a slight bit off level to make it more difficult. The first float setting gave me nice high end speed and crappy rough low end, the second float setting has given me much more low end power and smoothness, but there is no high end to speak of, unless I pull the "choke" cable a bit, then she starts to roar. I am not sure if it is the air or fuel from the choke circuit that is bringing the high end to life?
I will keep fiddling with this CNS carb, but I am tempted to get an NT and try it out to see how she runs with that. This CNS has been pretty tough on me, I mean, she runs, but no matter what the settings I can't seem to get good idle and solid pull in low and high range of throttle....
These are the only carb choices I am aware of, CNS and NT, I am wondering if there are more?
Thanks in advance to anyone who has info to share....
 
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