Problems with new kit...

Discussion in 'Motorized Bicycle General Discussion' started by Redpx, Sep 5, 2010.

  1. Redpx

    Redpx New Member

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    I am having problems with my new kit. I can start it but it will not idle. I got the grubee 48 cc which I am running on a Genesis Mountain bike with 29 inch wheels. The cns carb came with both the air fuel mix screw and the idle screw glued. I got the air fuel mix screw moved but for the life of me I cannot get the idle screw to budge. I got to the point where I decided I wanted to torque the screw out and then just order a rebuild kit. The screw is brass I think and quite weak. I destroyed the screw and it still did not budge. I think that this is the reason my bike will not idle. There are a few other factors that I am considering too. I removed the tip off of my spark plug because I needed clearance from the top bike tube. The bike will run but it does not have much power and it will not idle. I dont know what to do about the idle screw now and I am desperate for some advice. I went ahead and order the nt carb from thatsdax and I should get it on the 8th. Is there a way to get that idle screw out and how would I go about adjusting the gear ratio since I have 29 inch wheels? What else can I try to get it to idle. I have adjusted the choke and currently have my air fuel mix screw at about 3 and a half rotations.
    The gas mixture is 16 to 1. Any advice would be greatly appreciated.
     
  2. Nougat

    Nougat New Member

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    You should be using at least 24:1 during break-in. That might be the whole problem. Drain the fuel and put in fresh 24:1 or 32:1.
     
  3. Redpx

    Redpx New Member

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    I thank you for you reply but my manual for my kit stated this:

    During the break-in period (1st gallon of fuel ), the ratio is 16 to 18 parts gasoline to 1 part oil. After the break-in period, the ratio can increased to 25 parts gasoline to 1 part oil. I was warned if the mixture is not right I could seize my motor.

    Is this information wrong?
     
  4. Redpx

    Redpx New Member

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    You know I cant wait to see if that fixes it I think I am going to try that right now actually. I am new so I dont know for sure, but you seem to have alot of posts and ill take your word for it. Ill post the results.
     
  5. Nougat

    Nougat New Member

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    Yeah, the Chinese manuals all say that. Supposedly it's because they use SAE30 in east Asia.

    Use 24:1 for break-in, and 32:1 after that, with regular non-outboard 2cyl oil. High end synthetics can go to 100:1.
     
  6. r00t4rd3d

    r00t4rd3d New Member

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    I wish someone would sticky this.

    DONT BUY THE CHEAP CNS/RACING/NT/ETC CARBS !

    If your going to spend money on a aftermarket carb get a 18mm Mikuni.

    18mm mikuni carburetor items - Get great deals on eBay Motors, Asian items on eBay.com!

    They are about the same price as the other carbs. They are tunable. Parts are simple to find. They been making carbs for years and years. They dont come glued. etc etc etc......

    :)

    Break it in at 32:1 just dont beat the nuts off it. That means no full throttle till you get a couple tanks of gas threw it. If you have been running 16:1 with the spark plug that comes with the kit your bike is gonna run like crap balls till you get a new plug and move to 32:1.


    roar !
     
    #6 r00t4rd3d, Sep 5, 2010
    Last edited: Sep 5, 2010
  7. BarelyAWake

    BarelyAWake New Member

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    OMG YOUR RIGHT WHAT HAVE I DONE?!?!

    lol - root, we're all thankful for the advice... but TBH I'm quite well satisfied with my CNS and until the Mikuni/Dellorto is offered at a similar price from a reputable vendor - I'll not be buying one.

    I simply despise ebay *shrug*
     
  8. 5446

    5446 New Member

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    Sooooo how did you get your CNS carb to stay put on your intake? (sorry for the hijack lol)
     
  9. r00t4rd3d

    r00t4rd3d New Member

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    You could slot the intake on the carb with a dremel and a cutoff wheel to compress like the stock carb. Or get some of that heat rating tubing they use for the exhaust and hose clamp each side.
     
  10. 5446

    5446 New Member

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    It came with a slot and I opened it up myself with my trusty dremel but how much can you remove before you take off to much metal from the slot? Can I just keep opening the slot untell it grabs? Should I use gas proof sealer to try to glue the carb onto the intake? (sorry again for the hijack)
     
  11. r00t4rd3d

    r00t4rd3d New Member

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    Maybe add another slot the same size on the opposite side. I dont have a CNS carb so Iam just guessing. A real hose clamp wouldn't hurt either.

    To seal it either get a o-ring , high heat silicone or an MM intake. An MM intake with a dab of high heat silicone would be unstoppable. You could forget about it.

    :)
     
    #11 r00t4rd3d, Sep 5, 2010
    Last edited: Sep 5, 2010
  12. BarelyAWake

    BarelyAWake New Member

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    I'd not cut the slot at all as there's a chance for a vacuum leak (it's pretty close already) and worse yet I've heard problems w/cracking if cut & compressed too much.

    I simply roughed up the end of my intake manifold a bit to give the spacer something to grip and added a touch of 'Seal All' (fuel resistant glue): Amazon.com: Seal-All, 3/4 oz: Home Improvement to the outside of the spacer to grip to the carby... tho I've removed the carb a coupla times since then & haven't bothered w/regluing - I think it's all the roughed up intake that's working for me.

    I've had absolutely no problems with carb movement or rotation - but I'm also not using the extended intake *shrug*
     
  13. BarelyAWake

    BarelyAWake New Member

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    It's just the nylon[?] spacer allowing the slip, cutting additional slots (or bigger) will just cause the spacer to compress - breaking the aluminum carb mount, the bolt they use to compress is actually far better than the NT carb's clamp so a hose clamp would be a downgrade ;)

    It's got an "O ring" included with it to help seal between the manifold & carb already - and I'm pretty sure you'd not be able to use the MM intake with the CNS as the carb itself is much larger (bowl would prolly hit the engine)... I dunno for sure as I'm not particularly a fan of the MM intake so I've not gotten one (I make & mod my own), the reported performance increase is no doubt due to it's reduced length and straight shot... but not only is there some potential for clearance problems, but often it places the carb at an excessive angle (req major float tab compensation, could lead to fuel starvation at WOT/max RPM and/or engine relocation) and ofc it's aluminum - nessasatating far thicker walls for strength which ofc means reduced flow (the ports are already FAR larger than the stock steel intake's passage)...
     
    #13 BarelyAWake, Sep 5, 2010
    Last edited: Sep 5, 2010
  14. Redpx

    Redpx New Member

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    Nougat it is running better but still not the results I am looking for. I am now running 24:1 and it idles for a minute or two then dies. I still have no power at all. It seems to run best with the choke all the way down. I am doing about 5 to 6 miles per hour uphill and about 10 miles an hour on level ground. My concern is my spark plug. A friend ripped the tip off for clearance to get the motor in with out the top being pressed tightly against the top tube. Could this be my problem with power? I found a cross reference page on these forums. Is there a low profile plug I should get instead? I read another thread that recommended the champion CJ7Y for 2 stroke motors. I bought that plug but the threads on it seem to be a millimeter or two shorter then the one that came with the kit and it didn't cross reference on the site I linked to that plug, but then again the reference site does not tell if the plug is a low profile plug. I've got the Tri Spark LD Z4JC. I also ordered the NT carb for 14 bucks from thats dax for now. It should arrive on the 8th. I am also wondering if maybe its the engine tilt... Here is a pic of another mountain bike that has more of a tilt in the motor than I do.

    Thanx for all of your help so far. This is my first build. I wish I would have gotten a cheaper bike xD. I plan on building another bike next summer with the experience that I have gotten from this first bike.
     
    #14 Redpx, Sep 5, 2010
    Last edited: Sep 5, 2010
  15. Nougat

    Nougat New Member

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    If you have a slant head, you can remove the head and turn it around, so the plug slants the other way. If that will give you decent clearance, do it, torquing the head nuts to 120 inch-lbs.

    I'm not sure I understand what got ripped off of what, though. The only thing I can think is the wire end cap that goes on the plug got removed from the wire. If that was put back on badly, your spark will be weak.

    Could also be a bum plug, if it's still the kit one. NGK B6HS or one of the iridium equivalents is what you'll want.
     
  16. Redpx

    Redpx New Member

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    It was the little metal tip of the spark plug, it was just screwed off. Ill make a trip to the store tomorrow and Ill get that plug. Also I noticed today that the chain is running the back top bike tube that goes down to my wheel. Could I possibly put the tension bar and wheel on the top bar instead of the bottom one? One more quick question... I read in one of the threads on this forum that the kill switched should be hooked to the blue cable and not the white one, that overtime if hooked to the white cable it will destroy the cdi ignition coil. I will posted when I get it all worked out and thx again for the information.
     
    #16 Redpx, Sep 6, 2010
    Last edited: Sep 6, 2010
  17. killercanuck

    killercanuck New Member

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    First builds are fun. I wouldn't run the tensioner on the top, that's where all your power is going. Maybe you can turn your rear sprocket around for a little more clearance if you can. For your killswitch I keep this pic handy:
    [​IMG]

    gl.
     
  18. Nougat

    Nougat New Member

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    No, you can't put the tensioner on the top. If you need to change you chain alignment, try flipping the rear sprocket over. Most of them have the teeth offset just a little, and changing the direction of the offset might give you enough clearance.

    The kill switch can go to the blue and black wires to short the CDI, or to the white wire and ground to short the mag. You'll have better luck with the former.
     
  19. Nougat

    Nougat New Member

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    Another note about the sprocket rag joint:

    The rubber rags are supposed to be one on each side of the spokes. The instruction that came with mine had both the rags on the same side, which is just silly. If you have both rags on the outside, your sprocket is too far out. Put the sprocket back on right, and you'll be in good shape.
     
  20. Redpx

    Redpx New Member

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    Ok so the pic has a note that the black wire is grounded internally in the motor... do I still have to ground any wires to the frame?
     

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