carburetor issues?

Discussion in 'Motorized Bicycle General Discussion' started by xldh44, Aug 22, 2013.

  1. xldh44

    xldh44 New Member

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    I have a Grubbee Skyhawk, 66cc w/angle fire head and a Cns carb. Had a lot of trouble with when it when new bogging down and not accelerating at low speeds and cutting out at high speeds once it warmed up and got going. Got it all smoothed out. Took off stock air filter, used 6" x 11/2" tube attached a beer can with one open end and pantyhose over that opening to keep the dirt out; that helped a lot. Got a boost bottle that helped a little more. Installed an expansion chamber better yet. Tightened head bolts, put high performance spark plug and run with choke open on click and it's like night and day from where I started, but still not quite right. Runs great on the flats, bogs down a little uphill but I can give it more throttle and it will hold steady, although a lot slower from being on flat hightway but before if I did that it would bog down to a stall. On the other side however at even just slightly downhill that bike takes off like it got a shot of NOS; I mean it screams and it flies!! Is a float adjustment in order? If so how do I do that? My carb bowl is level horizontally but the front is slightly downhill vertically. If I can resolve this I'll have a virtually perfect ride! thanks
     
    #1 xldh44, Aug 22, 2013
    Last edited: Aug 22, 2013
  2. mapbike

    mapbike Active Member

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    Maybe I overlooked it but what is the problem you're having?
     
  3. dodge dude94

    dodge dude94 New Member

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    Adjust the float so there is a bit more fuel in the bowl. I had done this for a while and my low end was awesome but it bogged a bit at WOT at high speed. Wish I could find a happy medium....
     
  4. xldh44

    xldh44 New Member

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    @ mabike.... my problem is I lose power climbing and take off like a rocket on the down side of the hill. I would like to be able to smooth this out and maintain a consistent steady speed on both sides of the hill. I can't help but believe there is one particular thing causing this. I believe that "thing" to be not enough gas in the "bowl" and the cure is a float adjustment. If that is correct then I am a good guesser because I'm clueless about carbs except I have an idea it's a quick and easy way to get into big trouble. Before I tamper with the carb I'd like to know if that is the appropriate action to begin with and how do I go about making a float adjustment? thank you for inquiring, I appreciate it.

    @dodgedude uhmmm ditto! how do I do that? thanks for your response
     
  5. dodge dude94

    dodge dude94 New Member

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    You take the float bowl off, remove the float, and push downward on the little tab that pushes on the fuel needle that allows fuel into the carb. While you're in there, clean out any crap out of the jet and bowl. :D
     
  6. 2door

    2door Moderator
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    I'm afraid that "thing" is called gravity. Your bike is never going to go as fast uphill as down. You have to understand that you're only dealing with an engine that produces less than 3 horsepower. To expect for it to climb a hill as readily as it will go down one is just a bit unreasonable.
    It sounds like otherwise your engine is performing normally. Be happy with that and help that little 2 stroker by pedaling a bit up steep inclines.
    If you really want to increase your hill climbing ability you'll need to go larger on your rear sprocket size. Doing that will effectively lower your final gear ratio which will decrease your top speed but make hill climbing easier. It's a trade off. But no matter what; it will always go downhill faster.
    Tom
     
  7. Huffydavidson

    Huffydavidson STREETRACER/MANUFACTURER

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    Get rid of the CNS and buy a nt .
     
  8. xseler

    xseler Well-Known Member

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    I solved some of my problems by drilling out and removing the brass plug that covers the second adjustment screw.......the one on the left side.
     

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  9. xldh44

    xldh44 New Member

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    thank you dodge dude. And likewise 2door, I appreciate your taking the time to respond. Guess I didn't explain myself well. I understand and don't expect that I will fly up a hill and actually, yeah I do expect to slow down to some degree. It's the extreme difference between the two that has me believing something is amiss. I'm getting better at it but if I don't plan and adjust just right going into a hill (and I'm not taking steep) I can and sometimes do lose all power. On the downside of that hill, it's not just gravity. That engine cranks so fast I could almost do a wheelie! I get at least a 10 mph increase in seconds, that just doesn't seem quite right to me. My theory is that I fly down the hill because the decline all allows more gas into the bowl. My thought is perhaps I need a little more in gas in the bowl to start with and fare better in general. One thing I'm certain of, as it applies to these two stroke wonders, I got a gem of a ride! This my second build and I had constant problems with everything on the first one! After this experience what I believed then holds true now. My ignorance coupled with an inferior product gave me appropriate results. With this bike/kit I felt good with how I started and every adjustment felt I needed and made was in an improvement so I'm very pleased overall. I'm just into trying to get it to be the best it can be, not something it can't. I'll make this carb adjustment and it will work or not. If it does, well good for me, if it doesn't well, like you stated, I'm still in great shape with this bike. oh... I do understand the sprocket thing but it's relatively flat where I live so I'm good with the 44t that I have, thank you for mentioning that also. I'll let you know. Happy trails!!!
     
  10. xldh44

    xldh44 New Member

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    xseler, I thought about doing that. Can you make gas/air adjustments with the screw that you put in there? Also, you didn't specify what your problems were, was one of them the problem I was inquiring about? And for that matter, what were ALL the problems, if you don't mind my asking and are willing to share? t would be interesting and helpful to know. thank you
     
  11. xldh44

    xldh44 New Member

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    Huffy D. I thought of that also but I'm not convinced it's necessary. Seems likely I could have this particular problem with any carburetor, I'll tinker a bit longer and decide from there. thanks for your thoughts
     
  12. xseler

    xseler Well-Known Member

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    It was doing quite a bit of 4 cycling before. It ran OK, but using the left adjustment screw really dialed it in. Gained about 3 mph afterward. It runs a lot smoother also.

    I don't have any real steep hills in my area, but the inclines I do have are no issue at all with my set-up (66cc Skyhawk, CNSV3 carb, 44 tooth sprocket, and a home fabricated exhaust system)........still pulls 30mph up the inclines in my neighborhood. I also run a 50:1 Echo 2 cycle mix.

    Good luck in ironing out your little kinks!!
     
  13. xldh44

    xldh44 New Member

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    thank you X. Your comments and info have been extremely helpful!! Before I drill something I can't "undrill" (trust me, I've learned all my lessons the hard way) my plan for right now is to make a float adjustment first and see how that works. That said however, knowing me the way I do and reading the results you realized from what you did... it won't be many days before I'm in the automotive store, getting the tap and screw necessary to take this step. My automotive supply buddies will be seeing me soon.
     
  14. dodge dude94

    dodge dude94 New Member

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    You might be able to pop out the cap. That's all it is: a brass cap mandated for EPA emissions requirements. There is the air idle adjustment screw under. Basically you're drilling a hole, then prying it out.

    Simple simple.




    off topic, whereabouts in texas do you live?
     
  15. xldh44

    xldh44 New Member

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    hi X, awesome! I will definitely do that. I meant to tell you, my gas oil mix is 40:1 right now using Lucas semi-synthetic oil but I'm about to switch to Opti-2 which will allow a 100:1 ratio. I studied up on this a bit and found nothing but stellar reviews. Thank you again, I believe the info you and another provided is really the missing link and cure to having my ride run the way I believe it can.

    I live in Waxahachie which is approx. 30 miles south of Dallas.
     
  16. xseler

    xseler Well-Known Member

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    Yep......I just drilled a small hole, threaded a drywall screw, and pulled out the plug with a pair of pliers.
     
  17. mapbike

    mapbike Active Member

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    Your carb probably does need some fine tuning because all of the do out of the box, but just as Tom/2door mentioned, you will always hqve a lag going uphill and quick acceleration going down, my engines are broke in well and tuned well and I loose several mph on hills, if its just a slight incline not much is lost maybe a couple mph, there are other things that determine how much speed you will loose also, the condition of the wheel bearing, type of tires, air pressure in tires, weight of the rider and how long it is to top of the hill, get the carb tuned so that you are not 4 stroking at your typicql cruise speed of 25-28mph using the stock rear sprocket, then with properly inflated tires and with wheels that hqve good smooth bearings you will see how your bike will pull the hills, better exhaust and q few engine mods will make it do a bit better but we have a tendency to ask a bit much from these little china girls sometime, they can be made to give good rpm and top speed performanc when set up right, but they're not ever gonna be torque monsters and have loads of low-end pulling power.

    Best wishes and keep at it, and you realize better performance once the carb is dialed in better, just dont expect to much on the hills.

    Map
     
  18. xldh44

    xldh44 New Member

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    okay guys, here's the follow up. I had written inquiring about carb adjustments for my Cns because of "4 cycling" and difficult hill climbing. I was planning to make a float adjustment believing I wasn't getting enough gas in the bowl on the incline; xseler informed me that I had an air adjustment screw hiding beneath that little brass plug on the carb and having had success with that adjustment I might want to try it. I always try go for the less invasive and ideally reversible adjustment first and since his suggestion involved a screw, with precise adjustments either way vs. a manual bending deal with the float... I dug out the plug and made the air adjustment. VOILA!! Eureka, etc I had found it! I tried a few different adjustments in combination with my idle and choke and as good as that ride had been, excepting the concern I wrote about, it was even smoother yet. You might imagine my glee when I found myself racing up a hill instead of bogging down! It did not match the downhill speed (nor did I expect it to) but the point is that I could accelerate on the incline and maintain a steady speed of 20 miles an hour. So there lucky me, I accomplished what I set out to do; I believed my motor capable of better performance than I was experiencing and indeed it was. Thank you to all who took the time to respond and offer suggestions, they were all very helpful and I really appreciate it. It so nice to just go and ride and lose what was becoming the customary test run! thank you, thank you, thank you!! ride safe
     
  19. xseler

    xseler Well-Known Member

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    Glad it worked for you!! The members on here have experienced and tried a lot of things.......most of us are glad to share our findings.
     
  20. xldh44

    xldh44 New Member

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    ...yes I have observed that, this is a great site!
     

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