Need troubleshooting ideas... 70cc Dax with no power and sputtering out.

Discussion in '2-Stroke Engines' started by danhill, Oct 17, 2009.

  1. danhill

    danhill New Member

    I am getting a little bit frustrated trying to get my motor to run correctly. I am running out of ideas of things to check. I have a pretty good idea that the problem is in the carb but for the life of me I can not figure it out.

    This is a Dax bought happy time F80 70cc kit engine.

    I have only had this engine for about a week. I got it running monday and have been fiddling with getting the bugs worked out of the bike side and trying to get the engine to run correctly.

    When I first installed I had to adjust the forks on the floater down so that gas would not leak from the air intake. After I got that fixed the bike ran ok for about 6 miles but had somewhat low power.

    The problem:
    The engine will start just fine, but it has very little power. I am topping out at maybe 15mph. The engine sounds like it is bogging pretty badly even on flat roads. Now, after about two blocks the engine just stops. Once it has done this I can get it started but only will run for a couple seconds.

    Everything I have done so far:

    1. Tried every setting on the choke. It will not run in anything but the all the way down position.

    2. Moved the little needle on the throttle to every position on it. No change.

    3. Tried to find an air leak. To the best of my ability, I have found no air leaks.

    4. Blew out and cleaned every part of the carb I could find. No change.

    5. Checked exhaust for any blockages. Did not find any.

    6. Rode around the block with the exhaust off. A lot of power, but still engine still died.

    7. Checked spark. Getting plenty of spark through the wire, zapped the living !@#$ out of myself on accident.

    8. Checked compression. Compression was good.

    9. Cried like a little girl. No change.

    I am at a loss as to where to go next. I would try another carb but I don't have one and would rather not buy a carb if its not the problem. I am tearing my hair out trying to figure out this problem, I know there is so much fun to be had but instead I am sitting on my front porch learning out to disassemble/reassemble a chinese carburetor in under a minute.

    I need suggestions, been trying everything I could find on the forums and so far no luck. If someone thinks I need to check something from the list again go ahead and tell me so, I am new at this and may have goofed something up.

  2. mattysids

    mattysids Member

    Sorry to say, but it is VERY likely to be a bad carb problem

    these chinese carbs can break in any number of ways and it seems by the way you put it that the engine is recieving WAY too much fuel

    What color is your plug?

    If black and oily, the carb is the problem
  3. danhill

    danhill New Member

    It is a little too dark for me to go play with the spark plug. I will give it a look first thing in the morning. Does it matter if it is sitting over night or do i need to get the motor hot before I check it?

    I am almost to the point of just ordering a new carb to see if it makes a differnce haha. I will give this one the weekend before I give up on it.
  4. mattysids

    mattysids Member

    if the problem has been consistent, the plug will be black even without running it beforehand
  5. danhill

    danhill New Member

    Alright checked the spark plug and it didnt look very bad. A bit on the black side but it wasn't oily.

    Went through and cleaned the carb and rechecked everything. Added a better fitting O-ring between the carb and intake tube. Still the same problem. Ran fine about a block then died.
  6. srdavo

    srdavo Active Member

    To me, it sounds like the fuel flow to the carb bowl is NOT refilling fast enough to keep up with the amount of fuel used.

    Is your needle valve clogged?

    How about the screen in your fuel tank? Is it clogged?
  7. danhill

    danhill New Member

    Hmm, tore the carb and cleaned it out again so that is good. I will check the filter and if that is clean imma try bending the forks up further. Maybe I got them too far down?
  8. mattysids

    mattysids Member

    Did you ever bend up your float prongs?
  9. danhill

    danhill New Member

    Just got in from fidding with the bike. I may have found the problem.

    I took off the little brass hoo****er where the fuel line connects. There was a bit of black gunk down in it. I poked around at it with a safty pin and hooked everything back up. I have only rode a couple blocks ( its dark and it felt intensly dangerous with no lights) and it didn't die.

    I will ride a couple miles tomarrow and see how it goes. I am kinda wondering why the filter didn't catch that gunk. Might have been in there from before.

    Power was still a little bit on the low side, but at least I am to the point where I can start fine tuning.
  10. GearNut

    GearNut Active Member

    I strongly recommend getting a small in line fuel filter, such as used in professional lawn equipment. The "filter" in the gas tank is just a small screen that is really not much of a filter at all. It only stops small stones and sand from getting through. I doubt that this will be your cure, but it will save you from future headaches.
    With all the talk about poor cylinder castings, have you checked for excessive casting flash in the cylinder ports? How well does the exhaust and intake line up to the cylinder? Do a search on "match porting" to learn what I am referring to if you do not understand.