sputtering during ride...

Discussion in '2-Stroke Engines' started by Sandman, Sep 30, 2010.

  1. Sandman

    Sandman New Member

    Hello everyone, I'm new here and am having problems with my first bike.
    A little background, I have no 2-stroke or carb experience.
    I have searched but cannot find a solution to this issue, while I am riding my engine starts to sputter and is not at all responsive to any changes in the throttle. It will surge then idle repeatedly, and the only way I have found to stop this is to cut the engine and let it sit for a little bit. I have adjusted the choke both ways it can go, and it doesn't seem to have any effect, it still does it when I get up to speed (I don't know how fast, as I have no spedo.)

  2. Stan4d

    Stan4d New Member

  3. HeadSmess

    HeadSmess Well-Known Member

    hows the plug look when you pull it?

    sorta sounds like its not getting enough fuel possibly... so plug would be dry, not much smoke.

    letting it sit gives it time to refill the bowl... the surge is caused by the fuel level falling so low that the jet is only occasionally immersed.


    check the flow from the tap first to see if its the filter.

    if good, its more inside the bowl of the carb. undoing the drain screw with the tap closed should empty the carb, and if it doesnt start draining straight away when you reopen the tap... ;)
  4. Sandman

    Sandman New Member

    Well I have resolved that it is a fuel flow problem, and here is why.
    1.The plug is dry, and a bit dark, so I know my mix isn't right besides this,
    2. It stalls then it restarts after a bit of time sitting,
    3. I get the same reaction when I forget to open my pepcock when I start out (Imma newbie, so sue me)
    So, I took my fuel tank and carb and drained them, I tested the flow out of the tank, it was a nice thick steady stream. Then I tested the float height, it was right on the money. I replaced the fuel line and filter. I checked the air intake and found it without clogs or a stuck choke. I moved the C ring a couple notches and leaned out the mix a bit. Then I took it for a ride, and it didn't run short on fuel much at all. It's mileage was ****e though, so I screwed the throttle housing down a bit further and got that under control, but I am still running a dismal 80MPG, but the engine has not been broken in yet fully.
  5. motorpsycho

    motorpsycho Active Member

    80 mpg? that's pretty good.
    i think both of my engines only get about 1/2 that mpg on a good day
  6. Sandman

    Sandman New Member

    Well, I am having this problem again, but it is now only really popping up at night when the temp drops. I am stumped here, I have:
    1.Checked for air leaks with WD40, none that I can see
    2. Checked float height, it's kosher
    3. Moved the C-clip down, helped a little
    4. adjusted the throttle cable's height where it meets the carb, it is down low

    I am stumped, and everything I do works for a little bit then doesn't have much of an effect anymore. Now it is even revving sky high when I pop the clutch in, but my idle speed screw hasn't moved one bit. Also there is black, oily build up on the top front of the engine and at the intake of the carb, really oily. I pull my plug and it looks fine though, a very dark brown, so I know the mix needs a little bit of adjusting but not much. I'm perplexed, anyone have any ideas?
  7. Al.Fisherman

    Al.Fisherman Active Member

    With petcock open, remove the bowl drain screw and watch the fuel flow...if it's not a good flow then proceed....Cut fuel off at the tank. Remove fuel line from card with filter attached. Open tank petcock and watch the fuel flow. It should be a steady stream. If it isn't remove the petcock from the tank and watch fuel flow. At times crud is left in the tanks and block up the tank screen.
  8. motorpsycho

    motorpsycho Active Member

    popping in cold weather = lean.
    usually any time an engine pops out the exhaust, it's running too lean. colder air is more dense than warm air which means that your engine is getting more air sucked into the carb. more air - lean.

    a lean condition can also be caused by not enough fuel flow as al said. this would mean that the carb bowl is emptying faster than it can re-fill, and when the float bowl gets empty, it will lean out the mixture dramatically. this would attribute to high revs wit hthe throttle closed, popping out the exhaust and high engine temps.

    high revving when the clutch is pulled in = either it's too lean or your throttle slide is sticking open.

    wd-40 is not a good thing to use when checking for air / vaccuum leaks.
    you should use starting fluid because it is a lot more flammable. seriously, it will get into the smallest of areas and find air leaks much better than wd-40 will.
    Last edited: Oct 8, 2010
  9. Sandman

    Sandman New Member

    Well, I got rid of that problem, I pulled the throttle assembly out and reinserted it, but now I can't idle! If I don't give it a bit of throttle while idling then it just dies after a little bit.

    The fuel flow is running freely, I have checked it multiple times, and clean it all out every time I do. I guess my only problem now is fixing the idle, which is strange because the idle screw is all the way in that it will go, and it still dies.

    I'm getting to my wits end with this thing, fortunatly it still runs and can get me to work and back :) It is so challenging, and secretly, when I am not cursing it for acting up, I love it!
  10. motorpsycho

    motorpsycho Active Member

    make sure that you have the slide inserted into the carb correctly, the slide has 2 slots (one on each side, about 180 degrees across from each other). the slide can go into the carb 2 different waysbut only one of the ways is correct.
    there is a pin on the iside of the throttle bore on the right side of the carb. the long slot on the slide should be lined up with the pin, and the short slot in the slide goes where your idle screw is.

    if you have the slide 180 degrees off, you will not be able to adjust the idle because the idle screw has nothing to seat against. (if it is lined up with the long slot). The idle screw is tapered at the end and when it is lined up the correct way, with the short slot, the screw seats against the top of the slot. when you screw the idle screw in or out, the taper will raise or lower the slide.
    BUT....NORMALLY if you have inserted the slide the wrong way you will not have any throttle response or you will have wide open throttle all the time.
    if the slide was put in wrong, it can get bound up on the pin and it will not move at all, or the pin will be lined up with the short slot, holding the slide open at about 1/2 throttle.

    but you say that it runs fine and you just can't adjust th eidle.
    it is very possible that you inserted the slide the wrong way and either damaged the slide, or broke the pin that's in the carb. if you take the top off the carb. and remove the slide, you can look down the throttle bore and see the pin. make sure that pin is still there. i am thinking that you may have broken the pin off (it's pretty small) by possibly forcing the carb slide into the carb , or you may have damaged the slide.
    i am thinking that if the pin is gone or the slide is damaged, the slide will still be able to move up & down with the throttle, but the idle screw is not lined up with the short slot.

    i.e. the slide is just in the carb randomly and if the pin is gone there is no way for the slide to be clocked in the right position.
    does that make sense?
    Last edited: Oct 9, 2010
  11. HeadSmess

    HeadSmess Well-Known Member

    :lol: my mate pressed that lil pin out of the way on his! i thought it was just missing til he said so...

  12. ChiefGeek

    ChiefGeek New Member

    I'm curious how this ended? What was the solution to the problem?
  13. V 35

    V 35 Member

    Considering how cheap, and how important, the carb is, a spare one is a good idea. You may have problems with the casting itself ?

    I put a new carb on a Honda lawnmower, ran good, than died out, wouldn't start. I drained the fuel bowl and got about a Pepper
    Packet full of black grit in Gas. I checked the fuel, nice and clean. realized the grit came from the carb itself, as the problem never re-occurred.