New Build, Starts WON'T Accelerate!

Discussion in '2-Stroke Engines' started by katelen101, May 26, 2008.

  1. katelen101

    katelen101 New Member

    I just installed a 70cc 2stroke. It starts up and runs, but will hardly accelerate at all, if I didnt pedal it would barely would forward. Is this common with new bikes? I got it from thatsdax and supposedly it can get up to about 35? Any suggestions or similar experiences?

  2. Does it stall when the choke is on? Might be air leak, or might check the needle setting in the carb.
  3. eljefino

    eljefino Member

    Is it making noise and blowing hot exhaust? Possible you're just turning the motor over and it's not actually adding power, just making a burbly noise as it pumps air?
  4. HoughMade

    HoughMade Guest

    Does it rev up fine when the clutch is pulled in?

    Does it rev with the clutch out, but without acceleration?
  5. fordtech

    fordtech New Member

    spark plug gap

    my best friend just built his first motored bike and ran into the same issue, he asked me to look at it. first thing i did was pull the spark plug and it had an unmeasurable small gap, so may want to check that, mine is at .027 runs great
  6. check compresion as well.


  7. (Ian)

    (Ian) Member

    I'm having a similar problem. Were you able to solve yours?
  8. 210061741

    210061741 Guest


    Check for spark.

    Bad coil.

    Is the plug wet.
  9. Bezzi1

    Bezzi1 New Member

    Bro I'm having that exact prob my motor starts but makes a gurgly sound when I try to acclerate sum1 plz help .... I just built the bike and it ran a lil before doing this
  10. Anhevius

    Anhevius New Member

    Here's the basic troubleshooting checklist for all petrol motors:

    1. Check for spark. Pull the spark plug out. Put the boot back on it, and ground the plug on the motor (metal to metal contact). Turn the pedal of the bike with the clutch in gear, and look for spark.

    2. Check spark plug condition. Did you foul it with anything? A little brake cleaner will do wonders for it if the plug isn't nice and clean.

    3. Shine a light down the spark plug hole. Look and see if there's fuel puddled on the piston. If there is, tighten down on your carby to restrict the flow more. With any carbureted motor, there is going to be fine tuning to get proper flow.

    4. Check for compression. If you're in the US, you can get a compression tester kit from AutoZone or Advance, and you'll get your money back when you return it in good condition.

    5. Check your chain. Make sure it's not too tight (there is such a thing) and providing too much resistance against the motor. If the motor can't spin properly, then it'll bog down.

    Though to me it sounds like bad spark/too much fuel. When you start it and it idles, do you get exhaust that smells extremely powerfully of petrol? If you do and no smoke, you've got no spark. If you're getting stinky black smoke, you're flooding the engine.
  11. KCvale

    KCvale Motorized Bicycle Vendor

    You do realize this was a 4 year old topic before posting in it right?

    With no pics of how your engine and carb are mounted but that 'choking' sound you hear is usually just caused by raw fuel pouring into the crankcase because you left the gas shutoff on when parked or the carb angle is at so steep and angle fuel just flows in running or not.

    Try this...
    Turn off the gas.
    Pull the plug.
    Go pedal it up and down the street a couple times with the the clutch out like you are trying to start it but don't give it any throttle.

    That will blow out all the fuel sitting at the bottom of your engine making that gurgling sound.

    Put the plug back in and try it.
    If it runs find out what is causing raw fuel to flow into your engine and fix it.
    Bezzi1 likes this.
  12. butre

    butre Well-Known Member

    when I first got my bike the plug was gapped at around .010 and wouldn't run properly. I gapped it at .035 and it immediately ran as it should have been
  13. Bezzi1

    Bezzi1 New Member


    First off thanx for the help bro ... I really appreciate it...ok so far I just went and got me an Ngk plug because the I heard the Chinese stock plug are no good... And upon taking the old one out i noticed it was kinda of wet and and darkish and it smelled like gas i tried the spark test with it and got some spark tho ....yesterday when I tried to ride I noticed the muffler was dripping like an oily black liquid that smelled like gas so with that said I think it is bad spark and too much fuel.... So what should I do now? I going to put the new Ngk plug just to have a better plug anyways... Is there anything else I should do ? Or some type of way I should start it ?.... And I haven't gotten it to idle correctly yet... And once again bro thanx for the help
    Last edited: Aug 16, 2014
  14. Bezzi1

    Bezzi1 New Member

    lol i realized it after i i was jus like "f" it....but here are some pics i just took of the spark plug and engine mounted up photo 2.jpg photo 3.jpg photo 1.jpg

    Attached Files:

  15. Bezzi1

    Bezzi1 New Member

    and im going to do that asap to blow out the fuel thanks for the help
  16. KCvale

    KCvale Motorized Bicycle Vendor

    Ya, that is one soaking wet spark plug.
    Either your carb float is off and it's dumping raw fuel into the engine or you have no spark.
  17. Anhevius

    Anhevius New Member

    You're getting WAY too much fuel. The plug should never be wet, considering it's pretty much on fire constantly. You'll need to re-tune your carb, and make sure you've got good gap on your plug. A gap tool is only a dollar or so.

    The NGK is the right way to go. With kit motors, I NEVER keep the stock plugs, except as an emergency spare. (I always keep a few tools on me. A portable socket set and a spark plug socket)

    When you get the plug, you need to consider the environment you're in as well. Any plug will work, but the right plug will work better. If you're in a cool/temperate area, range six is great. If it's extremely hot (like Florida and Texas in summertime hot) get a range five. If you have cold winters, get a range 8 plug for that time frame.

    It's a little change, but even a 1% increase in operation efficiency can increase the lifespan of your motor and mean more fun with it.

    Good luck and let us know how it goes!
    Bezzi1 likes this.
  18. Bezzi1

    Bezzi1 New Member

    ok guys thanks for all the advice ...i did some work on the carby last night and blew out the fuel in the engine ... im going to try it out now and give you guys an update later thanks again... i think i've been puttin gthe choke up too much thinking it was a gas issue...
  19. Bezzi1

    Bezzi1 New Member

    ok guys i put the new plug in....and the carb isnt leaking anymore but its stilll not accelerating ...sounds like it wants to but isnt do think it might b the kill switch thats causing that?
  20. Bezzi1

    Bezzi1 New Member

    ok i put the new plug in....and the carb isnt leaking anymore but its stilll not accelerating ...sounds like it wants to but isnt do you think it might b the kill switch thats causing that?