vent hoses on a CNS carb

GoldenMotor.com
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
Got a CNS here and it has a hose near the enrichment plunger that I'm thinking is to deliver air to that circuit - sound right?

It has a vent near the idle speed screw with no hose that I'm thinking is the vent for the bowl - yes?

Also has a hose that has been sealed off near the idle air screw that I'm thinking should be opened to allow for mixture adjustment at idle - yes?

anyone know about these
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
searched here a lot & around net - pics all seem cut off at borders before the ends of the hoses can be seen

guy broke almost every part of this POS bike including ripping back of the cases off, not really wanting to trace all passages in carb too : (
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
looked more and found some post about the hose at the idle air screw that said it came from shipper with that hose melted closed, but it wouldn't run right - no indication if that hose should be opened or not : (

other pics I found show the carb without anything above the air screw

all this carb says on it is a big "YD" near top of body
 
B

bill2781

Member
May 24, 2013
239
0
16
okmulgee OKlahoma
I found some pictures that will tell you what you need to know I jus gota figure out how to post them for you. heres a linkhttps://www.google.com/search?site=&source=hp&q=pics+of+cns+carburetor&oq=pics+of+cns+carb&gs_l=hp.1.0.33i21.2981.7207.0.9800.16.16.0.0.0.0.169.1907.6j10.16.0.stareuni...0...1.1.32.hp..5.11.1463.VLEbHYxaRXU thers pictures of the carb and has wording to tell whats what.
 
Last edited:
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
thanx, been thru google pics - looks like there may be several models of these that changed over the years

most new ones don't even have vents where I got hoses

got enough of the bike together to run it an hour or so ago

seems to run OK on the bench - air mix hose seems to make no diff if it is open or has the plug over it (air screw hits a sweet spot at 3/4 turn whether air is open or closed, but not a big diff either way)

I don't like these CNS things, so as long as I have it running, I'll not worry if hoses are right.
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
that would sound right if I didn't have three hoses (four if you count the bowl drain on the bottom)

after running it in the bench yesterday, I finished it up today & tried a ride - not pulling over about 1/3 throttle, but my back is shot for the day & I'll look at it tomorrow
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
yes, that is a good pic except that I have another hose on the other side right under the enrichment plunger and the air mix screw is not inset, but sticks out a bit from the side of the carb

bike looks to be at least a year old, so I was thinking it should have run better, but maybe it was always like this (might just pull an NT off the shelf, as we don't run CNS here on unmodified HTs)
 
xseler

xseler

Well-Known Member
Apr 14, 2013
2,886
151
63
OKC, OK
crassius said:
yes, that is a good pic except that I have another hose on the other side right under the enrichment plunger and the air mix screw is not inset, but sticks out a bit from the side of the carb

bike looks to be at least a year old, so I was thinking it should have run better, but maybe it was always like this (might just pull an NT off the shelf, as we don't run CNS here on unmodified HTs)
Click to expand...

I've just received a selection of smaller jets to help tune my CNS --- it runs OK (33mph is the top so far on a 44t sprocket), but I'd like to get it a little smoother/leaner/mo betta.

I can say that when I took this bike to the mountains of New Mexico, I never did get it to run right, no matter the adjustment. I think that a much leaner jet would've helped a lot!

Good luck!
 
a.graham52

a.graham52

New Member
Nov 22, 2013
232
1
0
island of misfit toys, maine
If u check again you will find one hose has vacuum. The only vent even nessasary on a carb is a vent for the bowl. The other "vent" is manifold vacuum port just like on motorcycle and most other carbs.
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
well, then it is not a "2"

looks similar to what I've seen on honda 2-strokes from the late 60s-early 70s
some had a vac line to open the petcock & some also had an inlet for oil from the pump

dropped the needle to last notch and it runs quite fast at 1/2 throttle now (about the same as an NT carb at full throttle), but won't climb a hill - I could solder the main leaner, but am pretty sure the stock HT motor isn't going to pull enough volume to get a good mix out of this carb
 
a.graham52

a.graham52

New Member
Nov 22, 2013
232
1
0
island of misfit toys, maine
iv had great luck with this carb! first installed a bigger air filter (less air fuel adjustment necessary from the start!), saudered my main and adjusted the needle. the only thing i have thats not perfect is the pilot circuit taht im saving for next spring.

just remember, if you adjust your main, you will have to adjust your needle again most likley.

for ****s and grins, heres my carb:
 
Last edited:
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
not in a big hurry on this, so will just let it sit a bit - last time I did a main it was solder. drill, resolder redrill, several times to get it right
 
xseler

xseler

Well-Known Member
Apr 14, 2013
2,886
151
63
OKC, OK
I just got a selection of jets. I'll post up the results when the weather turns a little bit better.

Said the factory jet was about equivilent to a 72. So I got a 70, 68, and 66.
 
You must log in or register to reply here.
Top Bottom