2011 skyhawk GT5 carb question...

Discussion in 'Motorized Bicycle General Discussion' started by T to the IMMAY, Apr 13, 2012.

  1. T to the IMMAY

    T to the IMMAY New Member

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    ok, first off...im a newb with MB`s and some people will say im as mechanically inclined as a fart. but i did manage to assemble the 2011 skyhawk GT5 kit and install it on my 4 year old walmart schwinn skyliner in less than 4 hours! ;) but i am having trouble with one little thing....

    Q- there are 3 small tubes coming out of the motor. one i know is the fuel overflow but what are the other two tubes for? they seem to stick straight up.
     
  2. NunyaBidness

    NunyaBidness Active Member

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    Pictures would help.
     
  3. T to the IMMAY

    T to the IMMAY New Member

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    haha yeah good point, here is a pic of the motor and the two tubes that stick straight up. what are they for?

    [​IMG]
     
  4. Al.Fisherman

    Al.Fisherman New Member

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    #4 Al.Fisherman, Apr 13, 2012
    Last edited: Apr 13, 2012
  5. halfevil333

    halfevil333 New Member

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    Beh, I've heard a TON of complaints about this carb' but if you follow the instructions above for the tubes, and get a billet intake from pirate cycles you'll have few problems once you get the air/ fuel screw set....
    These take a bit more patience, but perform just fine..
     
  6. T to the IMMAY

    T to the IMMAY New Member

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    thank you VERY much guys :) you have been extremely helpful.
     
  7. nightcruiser

    nightcruiser New Member

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    Al. tells everyone to throw away their CNS carb, I'm not quite sure why...

    The CNS is a bit harder to understand and tune than the basic NT or speed carb, but they are good carbs when tuned properly. Here is some basic info.

    The standard NT or Speed carbs have a single fuel jet and an air choke on the carb. The CNS carb has a main fuel jet, an idle fuel jet, and an "enrichment jet" which is attached to a lever which richens the fuel mix for cold starting (in place of an air choke. Some scooters use the enrichment method rather than an air choke, often controlled by an automatic plunger rather than the manual lever on the CNS). So the CNS IS more complicated than the NT or Speed carb.

    Things I have noted about the CNS, the idle jet is VERY SMALL and can clog easily. This will cause hard start condition and rough running in lower RPM range. I use a very thin wire (wire brush bristle or bare wire from a garbage bag twist tie) to ream through the idle jet when I clean the carb because carb spray had not been effective for me. When your kit is freshly installed you might get a little debris down your fuel line that could easily clog this idle jet, so make sure you keep it clean. If the carb is sitting off level you might need to adjust the float to get her running right. The main jet might be a bit small...

    I have a CNS V2 carb, slightly modified at this point, haven't had one of the V3 in my hands yet.... That said, the three tubes you were asking about, the bottom one is the overflow, keep that tube pointing downward where it can drain away excess fuel if there is overflow. The other two just need to be open (connected to nothing). On my V2 carb one of them go into the air filter, I originally had the red plastic air filter, while your V3 should have a high flow cone style filter. Also, I hear the air mix screw is capped off on V3, and may be screwed in fully under the cap (a turn or two out would normally be a better position). Someone had reported that the cap comes off easy enough by drilling a hole in the cap and prying it off, then you can get at the air mix screw.

    I don't want to go into giving tuning advice before you post feedback on how she runs right out of the box, so post back on how it went and we will try to help you get her tuned up...
     
    #7 nightcruiser, Apr 13, 2012
    Last edited: Apr 13, 2012
  8. T to the IMMAY

    T to the IMMAY New Member

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    WOW!!! awesome info :) thank you :)

    I have had it all put together and running since yesterday and now its all rainy looking here so im not gonna have any real feedback for you for a couple days maybe. but as soon as i have some ,I will post it here.

    *I still think i might order the NT carb and see how that performs?????*
     
  9. nightcruiser

    nightcruiser New Member

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    I thought the same thing when I first started working on my CNS carb. Once I got it running right I forgot about that right away, mainly cause I would have to change over the throttle cable when I change carb, and I am plenty happy with the CNS after I got her tuned up....

    Glad you got her running already, seems like you did well. If you have good throttle response through the full range you should be good to go. If she bogs down at a certain point you might need a little tuning.

    As for throttle response, on the CNS:

    The idle jet, air screw, and idle screw have the most effect at idle throttle.
    The needle position has the most effect for mid throttle response
    The main jet has the most effect at WOT (Wide Open Throttle)

    Lets hope yours is running smooth through the whole range and you wont have any special tuning to do....
    Enjoy!
     

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