so i need your opinion please

Discussion in 'Motorized Bicycle General Discussion' started by twostrokejimmy, May 14, 2014.

  1. twostrokejimmy

    twostrokejimmy New Member

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    im looking to upgrade my 49 that's ported and port matched and milled down head and can its pretty snappy now but what would be a good carb middle of the road ya know thanx dnut
     
  2. 2door

    2door Moderator
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    What carburetor are you using now?
    With no more done to the engine that what you've listed you won't get much better performance than with the good old NT or NT Speed carb. They'll both provide you with good all-round performance, easily tuned and basically troublefree. Just give them clean gasoline and they'll work well for you.

    Tom
     
  3. twostrokejimmy

    twostrokejimmy New Member

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    huazhong that's all I see it dosnt look like a lot ive seen round so just a good upgrade is all I need
     
  4. mapbike

    mapbike Active Member

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    One of my fastest bikes is running a NT Speed Carb as Tom suggested above, it has good power and I can cruise all day @ 43+MPH on the flat without a head wind, I weigh 215lb currently.

    I'm running this carb on a stock Dax GenIV lower and I have done all my own rookie port work on the jug and I have a Cat eye pocket bike expansion pipe with about a 12" header pipe going to it, a stock CDI ignition and a 34T rear sprocket on a 26" wheel, I had a 70cc hi hi Puch head on this engine before putting a 6cc fred head on that I bought used from a forum member last year, the "fred head" made no realized performance gain over the Puch head but it's shiny and will be replaced by a Jakes Diamond Head when they are available...LOL

    I said all of this to let you know that with the right engine and set up, a reliable bike that will cruise at 40+ mph can be had with a simple and inexpensive NT or NT Speed Carb, no big honking carb is required to have a 40+ mph bike if everything else is right, and on the other hand if your bike wont do 40+ mph with the NT carb, it wont do it with a bigger carb either because most of the time the carb isn't the limiting factor for good power and MPH with these China Girl engines unless the engine is extremely modified and very well balanced.

    A good-well balanced 66cc with a well tuned carb, good exhaust that isnt to restrictive, a correctly ported jug, enough compression, wheels on bike that roll easy, correct gearing and the right fuel/oil mix = good performing china girl bike build.

    I can tell you that no matter what you do you will never get the power, torque or speed from the 49cc as you can get from the 66cc, but you can get all it can do from a NT Speed carb that is tuned right.

    Old Hot Rodders saying is " There is no replacement for Displacement" and this also applies to these little china girl engines when it comes to power, torque and top speed.

    Map
    dnut
     
    #4 mapbike, May 16, 2014
    Last edited: May 16, 2014
  5. Davezilla

    Davezilla New Member

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    I agree about teh NT and speed carbs, with the right jet and needle settings, there's not really a need to go bigger even after a few good mods.
    Personally I don't like the Speed carb, but it's not the actual carb I hate, it's that fuel shutoff valve that was giving me all kinds of trouble shedding off rubber particles and blocking off the main jet or keeping the needle and seat valve from closing so the engine would either starve at the worst time or it would flood. I finally gutted out the fuel valve and sealed it off, problem solved.
    The NT carb just has a fuel inlet so it don't have this problem and will perform just fine even after a few good engine mods.

    Right now I'm running a CNS on mine and I'm really liking it, the CNS doesn't come without it's problems tho... First and foremost, the CNS won't just clamp to the stock manifold, the plastic shim leaks like crazy, and it comes jetted too rich.
    When I installed the CNS on mine, I took out the plastic spacer shim and threw it in the nearest trash can and used a 3/4" long section of 3/4" ID silicone hose to take up the space, then used RTV on the outside of the clamp and stuffed it into every void and opening on the clamp, then installed it to the manifold and let it cure overnight.

    After it cured I installed the manifold onto the engine with the carb preinstalled on the manifold, connected the fuel line, turned the fuel on and checked for leaks, no leaks, gave the starter a quick pull and it fired right up. It didn't stay runnning because the choke (or enrichner in this case) wasn't needed and the idle was set too low, but with choke off and idle adjusted up it fired and ran.

    What I really like about this carb is that it has an idle mixture adjustment and once set, the engine idles smoother than ever and I can idle it under 1000 rpm, but that was just to see if it would, I set my idle at 1300 to 1400 rpm for regular use.
    Throttle response is nice,even set too rich so when I swap out the jet later on today it should be right where I want it to be and I'm thinking it should do good with either a #65 or 67.5 main jet.

    The other good plus about the CNS is it's a Mikuni clone and was used on the Yamaha PW80 and a few other 80cc 2 stroke yammys so extra parts are easy to get for it as well as you can upgrade it later on with a Mikuni rebuild kit. IT also has a power jet port already installed but this won't work just by connecting the overflow drain line to the port, you still need to regulate the fuel going in by making a restrictor (I'd start around .020 to .030" for restrictor size and adjust from there) and an air bleed to emulsify the fuel or it'll just flood the carb. I'm not using the power jet option yet but after break in I might tinker with it and get it working if I can't get the midrange to tune with the idle and top end tuned right. Power jets are really nice for compensating for altitude and temperature, and wher I live and ride, I really don't have those extremes so it most likely won't be worth messing with, but it's there if needed.

    My final opinion on the CNS carb is that it's a really good carb when you have bigger mods like more advanced porting, higher compression, and a good pipe. With it's easy tunability one could dial in just about any setup.
    For bikes that are close to stock or even with some more serious mods, the NT will do just fine and it's easy to set up, just get the jetting properly and the right needle setting and you're set... real easy and low maintainance as well as long term reliability.
    The Speed carb, I wouldn't run out and buy one, but if the bike came with one it's a good carb, I'd recommend getting rid of the built in fuel valve and using a regular banjo fitting there, just shut of the fuel at the tank petcock. The Speed carb is another "bolt on and go" type carb that's very low maintainance and easy to tune by changing the main jet and setting the needle, once set there's nothing left to do but ride.

    NT or Speed for stock to moderately modified engines CNS for those who like to fine tune everything, and no real need to go bigger than 15mm unless you're looking for serious power with reed valves or other major mods. For most people, the NT will be the best choice.
     
  6. mapbike

    mapbike Active Member

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    I've one of the old original CNS carbs I've had in a box sin e 2010, I have been thinking about giving it a try, just to see what I can get out of it on my strongest running engine which currently has the NT Speed carb, I'd like to see if I would notice any mid to upper rpm power improvement over the NT.

    Map
     
  7. Davezilla

    Davezilla New Member

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    You'll probably like it once you get it to seal on the manifold well. Mine is a bit on the rich side with the stock main jet in it so I got some smaller ones to dial it in with. I hadn't swapped the jets out yet today since my air filter duct came in. Since this carb is a PW80 clone I ordered up a PW80 carb inlet duct since it's just the right size and shape to let me run an air filter in my tight frame... I'm really happy with the way it fits and looks, but may need to make up a support bracket for the filter since it can flex pretty far on it's own...

    [​IMG]

    [​IMG]

    [​IMG]
     
  8. mapbike

    mapbike Active Member

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    Looks good, should be easy to make a simple support to stop the filter from bouncing around, being a somewhat Redneck country boy type as myself mine may not look fancy but I'd have something rigged up pretty quick for that...lol!

    Map
    .wee.
     
  9. Davezilla

    Davezilla New Member

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    Lol... thanks, I think I can just weld a small tab somewhere close for the clamp to grab onto, that'll keep it from flexing... I still need to do a few more weld jobs on the frame to support my pipe better anyway then I'll be able to take it all apart and paint this thing...
     
  10. xseler

    xseler Well-Known Member

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    Zippy-ki-ayeeee!!

    For a simple 'temp' fix, you could loosen the hose clamp that secures the filter, slip a small black zip tie under the clamp, and then just 'zip' it to the down tube.

    High tech Redneck at it's finest!!
     
  11. Davezilla

    Davezilla New Member

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    Hehehe... Look at teh pics of my air filter closer and I'm sure you'll find a ziptie in there... I got some redneck engineering going on in my build too...
     
  12. Davezilla

    Davezilla New Member

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    Oops... forgot to mention there's also a 1 1/2" long section of 1" diameter pvd pipe that I cut a groove in on my lathe inside between the filter and the inlet duct to connect the 2 together, the clamp that holds the filter on was too wide for the groove on the duct so the filter got the clamp and the duct it's self got a black zip tie...
     
  13. mapbike

    mapbike Active Member

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    looks plenty good there Dave...

    map
     

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