70cc lost of power (help!!!)

Discussion in '2-Stroke Engines' started by arielatom300heps, Jul 6, 2008.

  1. arielatom300heps

    arielatom300heps New Member

    Can some one tell me what's wrong with my 70cc engine?

    Yesterday when riding to a mate's house I had it maxed out at about 55km/h when it suddenly reduced to about half power even those I had throttle at full power. I got off the gas and tried to accelerate up to speed again but it had no power. It would only get to about 30km/h and it took a long time to get there.

    When I arrived at my mate's house we took carbie apart and cleaned it out along with the fuel line with air compressor. Power came back a bit but it is only running at about 70% of what it used to and maxes out at around 40km/h.

    Can someone give me advice on what it could be?

    Last edited by a moderator: Dec 15, 2015

  2. GasKicker

    GasKicker Member

    My first thought is ignition. Is the spark plug fowled?
  3. stude13

    stude13 Active Member

    hi mark; sorry to say but i think you engine is fried. i believe it leaned out and burned the piston, ring and barrel. you will have to open it up to see. good luck mitch
  4. datz510

    datz510 Member

    Yep, pull the head off and see what the cylinder looks like.

    These engines dont live long running full bore. I've got mine geared to cruise at about 1/2 to 2/3 throttle to maximize the life of the engine.
  5. Stud may be correct.

    Also when Running lean And high revs for a period will Heat up your Lower rod Bearing Eventually seizing them.

    A dirty carburetor or Incorrect fuel delivery could give same Symptoms.
    A bad Ignition would give you A switch being turned on and off feeling.
    A bad Plug will give you the same effect but usually a plug works or it don't.

    I hope its nothing Major

    First thing to do is Check the Plug.
    If read correctly it will tell you a good story And you can usually rule out a few factors.
    Next check compression.

    If all is good try new fuel

    I hope its nothing serious .

    good luck



    Last edited: Jul 7, 2008
  6. arielatom300heps

    arielatom300heps New Member

    Thanks for all the helpful info & tips everyone.

    I will take the engine apart some time this week and see if I have fried any thing.
    Do u think it could have been because I was running it 98 octane unleaded petrol and not on 91 octane unleaded petrol

    I think I might have done some minor damage to engine but I would have thought if it was running lean and over heating then the power would have slowly gone away not suddenly like I experienced.
  7. datz510

    datz510 Member

    The octane wouldnt do anything bad to the engine. THe real question is whether the engine was being run all out full throttle for hours on end. That's what destroys these motors.
  8. arielatom300heps

    arielatom300heps New Member

    I think i might have found the problem.

    I took the carby apart completely and got some dirt out of it and now its running better.

    I checked spark plug and it was a browny/black colour and so i have read this means it was not running lean and that the problem must have been the dirt in the carby.
  9. Great news.:grin:



  10. Jakylpops

    Jakylpops New Member

    I've been having the exact same problem the last couple days, so I finally took my carb apart. The whole thing was nice and clean inside, not a speck of dirt anywhere...BUT...

    ...my float was half full of gasoline:mad::mad::mad:

    It had a tiny little hairline crack in the wall of the "donut hole". The crack was so small I couldn't even get the fuel back out, so I had to drill a little hole, drain the float, clean it up really good, then patch the holes with JB weld...still waiting for it to cure right now.
  11. kjparker

    kjparker Member

    You **are** using a fuel filter right?
  12. Mountainman

    Mountainman Active Member

    I like that JB weld -- just wondering how well it holds up while sitting in gas ? Mountainman
  13. arielatom300heps

    arielatom300heps New Member

    no i am not using a fuel filter.
  14. lildeezul

    lildeezul Member

    there could be your problem..

    if dirt gets into your fuel sytem, it can clogg up the carb, or worse, damage the piston and cylinder walls...

    put a fuel filter on there
  15. pilotpeat

    pilotpeat Member

    RE the JB weld and gas-I had a weedeater gas tank that had several small cracks in it that I repaired with JB weld, and they held for a year or two before the JB weld eventually fell off. I then re-repaired it and it held for a few more years. This was on a plastic fuel tank. What I've been able to figure out is the plastic has to be SUPER clean and if possible scuffed up with some coarse sand paper. (like 50 grit) I don't know about using it on the inside of the carb-if the weight of it will make the float to heavy or if it will stay on with all of the vibration.

  16. Jakylpops

    Jakylpops New Member

    Yeah, I scuffed it up good first.
    I put about 30 miles on it today and it ran great, but I'm not expecting it to last very long, I've used JB weld to repair pinholes in motorcycle tanks before and they've lasted for many years. Anybody know where to get a new float? or got idea for material to used in fabricating another one?
  17. Mountainman

    Mountainman Active Member

    Any chance you can solder the float ?? That would make for a real repair.. Don't see many - ever leak -- not wearing - rubbing any where is it ? Happy Riding from - Mountainman
    Last edited: Jul 8, 2008