Engine Trouble Engine randomly cuts out at full throttle even under no load (swapped everything)

Discussion in '2-Stroke Engines' started by x9a3k, Aug 9, 2014.

  1. x9a3k

    x9a3k New Member

    Hey there, I've been working on this for the last week or so and I'm at a dead end. I've been searching for an answer to no aval.

    My 66cc Grubee skyhawk recently started acting up when ever at full throttle even when the clutch is disengaged. It seems like it just gives out almost as if you are hitting the kill switch.

    I've swapped the spark plug, the spark plug cap, the fuel line, verified the fuel is flowing fine, the ratio and oil type hasn't changed in 2 years of use, everything is tight, I've tried stock caps and NGK caps, verified the gap on 3 spark plugs (one brand new never used), I swapped the fuel filter, verified the kill switch wasn't shorting, the clutch assembly was replaced 2 months ago, I tried my spare carb and apart from the ignition coil and the engine block itself everything else has been tested/swapped to fix this.

    I have spares of pretty much everything and have tested almost everything that would make sense.

    Anyone have any idea's what it might be? I have a new ignition coil/cdi in the mail right now but I figured it would be worth checking to see if anyone had any ideas.

    It's kind of embarrassing heading to and from work and having it just die and watch all the traffic pass me :p

  2. crassius

    crassius Well-Known Member

    did you drill a vent hole in the gas cap? - just had a bike today that did that & started right back up after opening the cap
  3. x9a3k

    x9a3k New Member

    I don't think it's pressure in the tank considering I've had the same tank and cap for a year but I have 3 spare caps laying around so I'll try that out when I get home tonight or try with it loose. I'll try any suggestions tonight/tomorrow morning after and before work. Worst case scenario my father in law is a mechanic and he's fixed stuff on it a few times.
  4. butre

    butre Well-Known Member

    fuel starvation is still a possibly, check for kinks in your lines
  5. x9a3k

    x9a3k New Member

    Line is perfect, I have tons of fuel line laying around and even cut out a new chunk to try. I also never used the stock line, I had my own fuel injection line which is way thicker and better quality. I even checked with the petcock attached and it's flowing perfect. I'll double check because I barely made it to work today and plan to pull it apart bottom from top.
    It just started happening almost out of the blue. Two weeks ago it was running fine as it has forever. Too and from work daily (30KM a day at least)
    Last edited: Aug 9, 2014
  6. crassius

    crassius Well-Known Member

    if it always restarts, I'm still thinking fuel, but could be overheating and doing mini-seizes

    or possibly a CDI heating up 'cause it's ready to blow out
  7. x9a3k

    x9a3k New Member

    Well I checked the fuel flow with the petcock again, still flowing fine, I tested with a loose (and no) gas cap and it still borks up. Everything is tight and no air leaks, I'm going to pull the carb apart in a bit and see if something might have gotten through the filter although it's unlikely as both carbs seem to stuggle.

    I'm wondering if something might be up with the clutch assembly because I had some issues with it in the past. Worst case senario I guess I'll just replace the entire engine. It's served me well for 2 years and easily a couple thousand km. I've been thinking about building a new one from scratch with the huffy frame anyways. Like so HuffyBoard.jpg
  8. crassius

    crassius Well-Known Member

    I once had a piece of gray lint from a rag hanging by one thread that was stuck on the main jet - same color as inside of carb - opened & cleaned it a LOT and never saw it, but when fuel was present it floated up into the jet & blocked it - just got lucky one time and saw it.
  9. HeadSmess

    HeadSmess Well-Known Member

    2 years... lots of mileage...

    one, crank seals?

    two... new rings and new cylinder/re-hone.
  10. x9a3k

    x9a3k New Member

    Hey everyone, just an update. I found the issue last week! I got home and sprayed some carb cleaner near the intake and it turned out to be an air leak! The gasket for the intake (which hasn't been touched since I installed this) was cracked, a new one with some silcon to seal it up got it running just like new!

    Also I am almost done building the new bike

    10557686_568244333285781_6152374020472796425_o.jpg 10479148_568244299952451_5449017170773722756_o.jpg

    It's got a custom welded exhaust pipe, will have fully functioning mirrors, turn signals, and break lights once it's done. It also has a custom welded gas tank holder. Still lots of work to do on it and hopefully the weather stays nice long enough for me to ride it :)

    Thanks to everyone for the help!