Need help...please read...

Discussion in 'Off Topic' started by roozterdvx, Nov 9, 2007.

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  1. roozterdvx

    roozterdvx Guest

    Hey guys, this isn't on a motored bike but I hope someone can chime in with some help...

    I had bought my kid a mini bike last X-mas. The bike has not been run since the spring. I brought it out and noticed fuel had leaked out through the carb. It was put away with Sta-Bil mixed in the tank. I refilled the tank, cleaned out the fuel bowl, and started the bike. The bike runs for about 30sec. then dies and is really hard to start, (full choke and throttle 1/2 open). I then drained the tank, and refilled with fresh fuel, same results for starting, fuel still leaking.
    I went on ebay and found a replacement carb...bought it. Installed the carb, got everything hooked up...fuel still leaking and starting is improved, (still not easy like it used to be), but no power. The only way to stop the leak, is to turn in the screw right above the fuel bowl completely, then the thing won't start at all because the fuel supply is cut off. Even with the leak, I took the bike for a ride. The bike has no power and struggles to move. I've tried adjusting the screw, from almost completely closed, to almost falling out and no change.

    I'm almost at my wits end...

    I don't know what brand motor this is, but attached are pics of the carb I bought, and some pics of an identicle motor i found on ebay.

    Does anyone know anything about these carbs or motors?

    Sorry about the long-winded post, and I know it's not a motored bike, but I could really use some help.

    Attached Files:

  2. Alaskavan

    Alaskavan Guest

    I was going to suggest a stuck float. But you replaced the carb. Hmmmm...
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Drain and clean the entire fuel system.

    if that doesn't work, install the engine on a bicycle, then fix it.:cool:


  4. Hmmmm....maybe the carb you bought is also bad....granted maybe not as bad as the original...but fuel leaks....if bad enough are definitely not good from a running standpoint or safety standpoint either....If you can verify that you have a good strong spark and remove the muffler to verify that it is not obstructed and the exhaust port is not all carboned up....I would have to say it is a carb problem....FWIW I had a weedeater engine with a leaky fuel line (very small hole....but do definitly check the fuel lines too....may actually be running down the carb making it look like the carb is leaking when in fact it could be a fuel line)...Anyways, when I replace the line....engine ran fine...
    Good luck and let us know what you find......
  5. Oh....primer bulbs can leak too...gotta find and stop the fuel leak(s) then hopefully all will be good....Lastly make sure any venting tubes for the fuel system are unobstructed.
  6. roozterdvx

    roozterdvx Guest

    I'm leaving work a little early today and will disassemble the carb and clean everything. I'll check the exhaust and fuel lines as well.

    Hopefully this works. I appreciate the help. I know it's not a bicycle, but I figured you guys have a wealth of knowledge about these little motors, so that's why I asked. I've been looking through forums about mini bikes but the they tend to have younger members generally and since I'm already a member here...well you know.

    I'll post any results.
  7. davidsis

    davidsis Guest

    Sounds like a float. see if your float is still floating make sure it is not full of fuel. and that that little arm attached to it is bent at the right angle.
  8. Alaskavan

    Alaskavan Guest

  9. roozterdvx

    roozterdvx Guest

    I disassembled the entire fuel system...cleaned every thing and reassembled.
    The bike ran a little better. Still some hesitation and power is not what it used to be. i spent some time adjusting the screw near the bottom of the carb, getting closer on the tune. From what I can tell, the screw on this carb is not for idle, it's for high speed. I pulled the plug to check the color of the tip, light tan, (ran the bike at wot...took a while to get there...then turned of the key and coasted into the draiveway.) I opened the screw out about 1 full turn and then made the same run, checked the plug...darkened to chocolate brown. Tried one more time with the screw 1 more full turn out...plug turned almost black. After all this, I put in a new plug, brought the screw back in 1 full turn.
    The bike has actually picked up some top end power, (it has a speedo which is electronic based on rpm..not the most accurate but this bike used to run almost identical speed to two other bikes just like it, (yes I have 3 of these and this is the only one giving me problems)), on the top end it pulls away with me on it from the other two.
    It still has some stumble/hesitation off idle, and the fuel is still leaking.
    I'm guessing the stumble may be too much fuel since it drips out of the throttle bore whether the bike is at idle or off.
    There is a tube which comes up from the bottom into the throttle bore and the is a rod from the top which goes down into the tube. When the throttle moves, the rod is raised up in the tube to allow fuel to pass, (the tube has a slot on the side). I can see fuel coming out of the tube with the engine off.
    I can't see any way of stopping this except by installing a fuel shut-off valve.

    By the way, you guys are great. I've learned quite a bit by searching a reading threads here at MBc. Even though I haven't seen anything here that matches this motor/carb...I've been able to relate much of the information here to get a basic understanding of how it operates.
  10. mickey

    mickey Guest

    Is sure does sound like a float problem. Either the float isn't floating or you need to bend the metal arms that connect the float to the float valve. Fuel should not continue to flow into the carb once the bowl is full.
  11. roozterdvx

    roozterdvx Guest

    there is no float or float bowl, only a primer bulb.
    The appearsto be some kind of fuel pump to this carb. There is a supply line and return line and a small port through the intake and into the carb for positve crankcase pressure pulse.
  12. mickey

    mickey Guest

    weird. What is inside the bowl-looking bottom of the carb? AFAIK, even on pressurized systems there's a valve of some kind to prevent the very type of leak you're describing. Did you happen to take a photoswhile you had the carb disassembled?
  13. srdavo

    srdavo Active Member

    besides the bubble primer....your fuel leak could prolly be the fuel lines.
    napa has fuel line for $1 per foot. sometimes the supply & return lines are NOT the same size. If your carb is leaking.... a cheap fix is, replacing it with a (better quality) carb from a broke-down weedwhacker. A lot of this stuff will interchange.

    Is you fuel tank mounted higher than the engine? (gravity fed?)
    Last edited: Nov 11, 2007
  14. roozterdvx

    roozterdvx Guest

    I have the old carb and will try to get some pics up in various stages of disassembly. I left my camera at work so it won't be until tomorrow.
  15. Just a mention ... you talked of using the choke lever only once I believe in the original post ... from past experiences I've had be certain of when you really need it on and off ... and check that it is truly turning off when you don't need it ... case in point is the 2 happytimes I have ... neither engine wants or needs the choke lever at any Ca. temp I've experienced .
  16. roozterdvx

    roozterdvx Guest

    attached are pics of the carb in disassembled state and complete...

    in the pics with the throttle open, you can see the tube inside the bore. the "needle" in the tube is raised up when the throttle is turned, exposing a slit in the side of the tube to allow fuel to flow.
    it's this slit in the tube which keeps letting fuel out even when the engine is off.

    I don't know how to insert the pics into the post so I attached them.

    Attached Files: