Carb issues

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devkan

New Member
I have the new style CNS on my 48cc grubee. After sorting through float issues (turned out to be fuel shut off needle upside down from factory). I now have the problem of having to cap the bowl vent (on top off carb) to get to run well. I was having to run with choke closed/on before I plugged the vent. I was thinking air/fuel setting and tried moving the throttle clip down 1 to richen. Now it runs better but I still have to leave vent plugged. I was just wondering if anyone had thoughts. By the way I have liquid gasketed carb to intake manifold to prevent air leaks and have a good seal on exhaust too. Also, thanks norm for the throttle video I think I could do that in my kitchen this weekend instead of the crackpot ideas I have came up with. Thank you for any help I will keep tinkering.
 
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That sounds like a way low setting on the float level inside the carb to me.
If the fuel level is too low inside the carb, then the jet(s) cannot properly meter the fuel ratio. The result would be a too lean (not enough fuel) air/fuel ratio. Keeping the choke partially or fully on will block most of the air flow and enrichen the resulting fuel mixture at the expense of good engine performance.
 
Seriously though, a 16mm CNS is overkill for a 48cc. They are meant for the 66cc, or a fully sorted 50.

Go back to the stock NT setup. It will work betterrerr on your 50.
 
Very good point!
The throat size of the carb needs to be matched up with the engine's displacement.
Too big and it will not develop the proper negative pressure difference in the venturi.
Too small and it will restrict the air flow.
 
Mr Gearnut,

The "choke" on a CNS carb is actualy a third fuel circuit, not a vane or butterfly.

It cannot block any airflow as such.

It can however richen the mix on the fly without blocking any airflow which is a good thing for long uphill hauls.

Fuel is a coolant for aircooled twostrokes.
 
Kewl thank you. Hmm ya one of my problems was fuel constantly overflowing. Looks like I need to readjust float level now. I have seen many people that use the CNS with a 48cc it can't be that bad can it?
 
devkan said:
Kewl thank you. Hmm ya one of my problems was fuel constantly overflowing. Looks like I need to readjust float level now. I have seen many people that use the CNS with a 48cc it can't be that bad can it?
Click to expand...

ok so with the "choke" being 3rd circuit it should not be looked at to stop airflow istead regs. fuel?
 
wildemere said:
Mr Gearnut,

The "choke" on a CNS carb is actualy a third fuel circuit, not a vane or butterfly.

It cannot block any airflow as such.

It can however richen the mix on the fly without blocking any airflow which is a good thing for long uphill hauls.

Fuel is a coolant for aircooled twostrokes.
Click to expand...

Ok... :o
It is an enrichener, not a choke.
That is a whole 'nother beast with a similar outcome.
Still accomplishes the same result, a richer fuel mixture.
Sorry........
*hides in the corner and watches curiously*
 
and thnx wildemere.....Lol after thinking that was a choke as advertised i was looking at the thing all wrong eh?
 
You are welcome.
I am glad that my wrong impression of that particular carburetor actually helped you.
Still, a bit embarrassing to me.
 
well i appreciate the help! I definately had wrong impression but now I know that it is s'posed to be closed and was lookin at backwards. :~)
 
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