piston rod broke

Discussion in '2-Stroke Engines' started by unintent, Dec 12, 2006.

  1. unintent

    unintent Guest

    I think the piston rod broke. While I am VERY handy with tools, I am not a mechanic and do not know all the correct terms/jargon for things, so try not too laugh too hard when I get the name wrong.

    Well I got the 70cc from dax and have been using it around 6 month and then all of sudden it starting making a loud constant banging noise from the piston area. I took off the head and it looks like the piston has broke away from the crank shaft. I didn't take the piston all the way out because it never quite came out far enough for me to grab a hold of. What I observed with the head off was when I turned the rear wheel by hand, with the clutch enaged the piston would indeed be pushed up but was not getting pulled down as I turned the wheel, so I guess the piston rod broke away from the piston. What I mean is as I turned the wheel, the piston would come up and then stay there. I would have to push donw on the piston for the action of the wheel turning to push the piston back up.

    Reading through these post I didn't really find a detailed break down of this motor but it woule apear I am going to have to uninstall the motor and the engine block separates into two pieces.

    Does anyone have any detailed directions for doing so I can avoid any "gotchas"? And more importantly is there a place where I can buy a new piston or piston rod or both if that is what I need? Also, might the rod be attached to piston with some kind of pin or nut and bolt and I can just possibly reattach the rod to the piston?

    Do you think this is fixable?

    Also I did find a piece of metal on top of the piston when i took the head off. The piston wall looked find as far down as i coudl see of it.


    Thanks In advance for any reply.

  2. Steve

    Steve Guest

    You should be able to remove the cylinder from the engine case after the head is off. ( However, you may have to remove the engine from the bike to do that.) Anyway, after the cylinder if off, you should be able to see the rod and it's connection to the piston. I did not look too closely at mine, but there will be a pin that goes thru the piston and the top of the rod. If you have a broken rod, and it still turns over, it will be broken either at the extreem top, or the extreem bottom.
  3. istbenz

    istbenz Guest

    i saw a 'parts kit' on ebay the other day for like 60 bucks. it had a whole top end and a bunch of other stuff. i don't know if this will work for you or not but its worth checking out. glad to have you on the forum :D
  4. unintent

    unintent Guest

    so you're saying, I take the head off and underneath that, I can take the cylinder off? There didn't seem to be any separtion or nut or bolt or anything. It looked like to me the whole engine was three pieces.... the head (the part the spark plug screws through) and the remaing piece seemed to be two parts right down the center. I will recheck when I get a chance but you think there is a possibility there is another piece that comes off similiar to the head and this is the piece the piston goes up and down in? Thanks again. I will repost when I get a chance to look again. Thanks!
  5. Steve

    Steve Guest


    Yes, the cylinder is under the head, and the two are held onto the crank case with four long studs. Take the four nuts off the top, remove the head, and then the cylinder will slide off of the studs as well.
  6. bird

    bird Guest

    if your piston rod broke your motor is pretty much dead. its realy hard to get the motors apart with out damaging them, the lower half of the motors are pressed together. i would just use it for the parts that are still good.
  7. Cookie

    Cookie Guest

    break down of engin and parts

    http://www.grubeeinc.com/ <<<break down of engin and parts
    Also call dennis Ph# 918 855-1807 he is the gurbee go to guy and he is real nice he has helped me quite a few times
  8. Edward

    Edward Guest

    Usually you must remove the engine from the bike in order to remove the cylinder due to clearance issues. Once the head is removed the cylinder can come off, the "gotcha" here is the gasket between the case and cylinder will act as a glue and some gentle prying on non-mating surfaces can help it up. Cramming a screw driver into the gap between the mating surfaces is a very bad idea. DON'T. The piston has a pin that slides through the connecting rod, the pin is held in the piston by circular wire clips on either side. A new gasket made of a thin material should be made before getting too much further into the project.
  9. unintent

    unintent Guest

    Thanks for all the good feedback. I already have the gasket material (lost the muffler gasket on day one!). I will try to remove the cylinder and hopefully I can just repair the pins. Thanks again.