The inside of my thrashed 66cc engine

Discussion in 'Motorized Bicycle General Discussion' started by mapbike, Jun 30, 2010.

  1. mapbike

    mapbike Active Member

    Joined:
    Mar 14, 2010
    Messages:
    5,380
    Likes Received:
    1
    Here are some pics of what I found today when I removed the head and jug from my #2 bike, the pics are not the best so I got a new camera and it isnt that good I guess, but anyway I think you can see well enough to tell what I'm dealing with here, I have a new piston, rings, cylinder and gaskets, but I can see that iI will need to pull this one all the way down and do a very good cleaning before I even think about putting it back together.

    I have not been into one of these engines yet so I'm not sure of the order I will need to take it apart, I know I will have to use my little puller for these engines to get the drive sprocket off, but ther is a question I have for anyone that has rebuilt one of these little engines.

    :My Question:
    The rod bearing in this engine has got what seems to me to be a farely good amount of up and down play in it, and as I hope you can tell in one of the pics, the roller bearings between the Rod the Crankshaft have maybe a 1/4" gap between them as if there are a couple of rollers missing, this just doesnt seem to be right and I would like someone who knows about this to let me know if the rod should have this up and down slack and if it is normal to have this amount of spacing between the rollers.

    I'm asking for someone with for sure knowledge on this to answer my question, I'm not looking for opinions from those who have not had experience with these motors, Thank You, I do not mean to offend but I need to know what I'm dealing with here I want to get this thing right when I go back together with it.
     

    Attached Files:

  2. CoastalCruiser

    CoastalCruiser New Member

    Joined:
    Apr 28, 2010
    Messages:
    338
    Likes Received:
    0
    Ouch! Oh! Ick! That sucker is Toast! You might save some pcs but it'd be cheaper to buy a new engine.
     
  3. 5446

    5446 New Member

    Joined:
    Jun 7, 2010
    Messages:
    84
    Likes Received:
    0
    I think I saw one on ebay being sold by bgf for $70.00
     
  4. mapbike

    mapbike Active Member

    Joined:
    Mar 14, 2010
    Messages:
    5,380
    Likes Received:
    1
    I bought a new jug, piston, rings, gaskets for $32 + shipping made it a total of $52.00, BGF sells the engine alone for $72.00 + $15.00 Shipping= $87.00 delivered, if the lower rod bearing is bad in mine I will just replace the entire engine and keep the one I have for parts, but I would like to save this engine if I canbecause it is balanced so well in the lower end, it ran so much smoother than my other one, I'm waiting to get an answer on the lower rod bearing question I ask above which will help me decide what I do with it.
     
  5. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    1
    I haven't blown one of these in paticular,but I can tell you from your discription and pic that is no longer a rod,the case may be good
     
  6. mapbike

    mapbike Active Member

    Joined:
    Mar 14, 2010
    Messages:
    5,380
    Likes Received:
    1
    The rod and the crankshaft are still intact, the pics make the lower part of the engine look worse than it actually is because of lighting and the fact that it is so dirty looking with the oil and the small Aluminum fragments that came from the scored cylinder and piston sitting on top of the crank area seen in the pic, my main concern with the motor is the up & down slack that I can feel when I hold the connecting rod between my fingers and move it up & down, I can feel some slack in it which seems to be movement between the rod and the roller bearings themselves, I would estimate it to be maybe .010 + or - a little.

    I am looking for someone who can tell me if this is normal for these motors or if it should have very minimal movement, the slack between these 2 points has me concerned more than anything else right now.
     
  7. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    1
    Isn't that a chunk missing where the bearings are showing,that would be the down stroke part of the rod (when it fires),,,might spray it with cleaner and look,a lot of metal went through the engine as it started to fail,,,where is the snap rings out of the wrist pin holes(pin in the piston)
     
  8. junked

    junked New Member

    Joined:
    May 2, 2010
    Messages:
    65
    Likes Received:
    0
    No, play between rod and crank is not normal and would only get worse very fast if you were to just replace the jug, piston etc. You probably have damage to the crank pin also, not just the bearing. I would buy a new engine.
     
  9. mapbike

    mapbike Active Member

    Joined:
    Mar 14, 2010
    Messages:
    5,380
    Likes Received:
    1
    Thank you "Junked" and all who have commented on this thread,

    I have many years of experience working on 4 stroke engines and have rebuild and modified many of them to stock and/or performance specs. but these cheap china 2 strokes are a new animal for me and since the rest of the parts in these engines seem to have such loose tolerances I was unsure about the amount of slack that is acceptable in the lower roller bearing between the rod and crank journal, this engine had a clacking & knocking sound to it from the very begginning and now I am thinking that this sound was due to the lower bearing having all that slack all along, from the way it looks there were never enough rollers place between rod and crankshaft from the factory, there is enough room to put maybe at least 3-4 more rollers in there, I bet one of those rollers got turned at an angle between the rod and crank and then broke under the stress and this may be what came up and hung between the piston and the transfer port in the cylinder, I know something did, because the ring retainer pins were still in place and intact when I pulled the piston out of the cylinder. well looks like this is a spare parts engine now, Dang-it and it was so darn smooth running for it's short clacking life.

    :-||
     

Share This Page