Sprockets Broken small chain engine sprocket

Discussion in 'Transmission / Drivetrain' started by tmotorbikepad, Apr 2, 2011.

  1. tmotorbikepad

    tmotorbikepad New Member

    I ended up having a tooth brake of on the small sprocket that is attached to the clutch (because of a fallen off chain). I ordered the new small sprocket but i am trying to figure out how to take of the broken one. Do I need to take apart the engine or can it just be taken of more easily?

  2. BiMoPed

    BiMoPed New Member

    there should be a special threaded puller with your kit that pulls the engine 10 tooth sprocket and the 2 gears on the clutch side.
    If you don't have one order it too
  3. tmotorbikepad

    tmotorbikepad New Member

    Thanks for the help but I need a little more; I am not very familiar with how the threaded puller works. I got the tool attached to the threads on the 10 tooth sprocket but once its on good and i turn it, It only pumps the piston. I can't figure out how to make the 10 tooth sprocket release from the engine.
  4. wbuttry

    wbuttry Member

    you need to get a piston lock to aid in removing the sprocket i think you can get them at small engine repair shops or maybe harber freight
  5. dougsr.874

    dougsr.874 Active Member

    There was a thread on here somewhere that suggested using a piece of small dia. rope by removing the plug and inserting the rope just before the piston gets to top of stoke. I tried it once and it works, however besure not to put the rope to far inside the cyld. as it will get caught in the ports...
  6. wbuttry

    wbuttry Member

    sounds like a winner to me
  7. tmotorbikepad

    tmotorbikepad New Member

    Sweet, I think im going to try that rope idea. Im also still wondering how that small sprocket comes off? . Is it going to just pop off once the threads are twisted down or are there other necessary actions to take for getting it off?
  8. wbuttry

    wbuttry Member

    im not really sure how it come off really i know it has a nut you take off and dont you use the puller that came with the kit and the bolt you turn should pull it off on the tool i think it is presure fitted with a key or something and when you put the other back on i think you tap it on if im not mistaken
  9. GearNut

    GearNut Active Member

    The rope trick works very well.
    1. Remove nut and washer that holds sprocket onto shaft.
    2. Remove center screw from tool and oil the threads on center screw.
    3. Oil the threads on the tool and carefully thread it all the way in until it bottoms out inside the sprocket. Take your time as it is easy to cross thread the darned thing and you do NOT want that to happen.
    4. Install the center screw of the tool back into the part you have threaded into the sprocket and tighten it well. The sprocket should either pop off or just slide off of the shaft as the center screw is tightened.

    Keep a watchful eye out for the woodruff key (a half moon shaped bit of metal) and don't loose it. You will need to reinstall it when you install the new sprocket.

    Also, the tools have a hex on the outside of the portion that threads into the sprocket, gear or clutch to let you hold it with a wrench, preventing it from turning, while you tighten the center screw.

    Using this feature of the tool allows you to use it without using the rope trick.
    Last edited: Apr 15, 2011
  10. monsterhobby

    monsterhobby New Member

    I'm not sure if this can be done on a bike motor but on small scale 2 stroke engines I don't like to use a piston lock so I have used what they call a hydraulic seal. what you do is you turn the engine over till you can fill it thru the plug hole with gas and not have it go down the admission ports take a bit of patience but that seal spreads the load over the whole piston not just pressing in 1 place. again I have never tried it on a bike motor.
  11. GearNut

    GearNut Active Member

    This is basically hydrolocking the engine. Quite effective indeed.
    The rope trick is quite harmless to an engine if done correctly though.


    Full instructions on how to to change your 10t small front chain sprocket

    First of all, GearNut is Very helpful, i used some of his info to fix my sprocket. Now it is so easy. REMOVE PIN FROM CENTER OF SPROCKET BEFORE STARING AND IF POSSIBLE THE BALL BEHIND THE PIN.

    as far as the rope goes,(the harder and more dangerous way) remove your sparkplug, feed a couple inches of rope in, turn the sproket slowly in the direction you want to turn,( to the left to remove nut and to the right to put it on) it will lodge itself between the piston and wall and stop it from turning. reverse sprocket to remove.

    the easier way: take your extra chain link from sizing your chain. run it in the sprocket in the top foward position to to remove nut. stop the gear from turning by lifting the first link in an make it jit a wall. use sparkplug tool to remove bolt. note: it will take force to loosen. remove bolt and jagged washer.

    next like gearnut said, oil the threads on the tool. carfully spin the outer piece into the sprocket until it bottoms out. (if you spin to the left first you'll feel it drop into the grooves.) take the center bolt for the tool (OILED) and spin into its spot on the tool. using an open end/closed in wrench put the fitting closed in on the bolt and spin clockwise. it will eventually become hard to turn (the oil helps ease this part) when you cant turn no more, turn with force, it will soon feel easy to turn and that baby is off of there. it will stay on your tool. before pulling away put your hand under the pin that the sprocket is on to try to catch a very small half moon/circle key that sits in a groove on the pin that locks that sprocket in place. if your lucky it will stay on the pin. THE KEY IS VERY EASY TO LOSE AND YOU S.O.L WITHOUT IT.

    To put the new sprocket on put the key, round side down in its slot on the pin(you will see how it's grooved). slide the sprocket on to the pin putting the grove around the key. tap with mallet or something of the sort. hard but not to hard, soft but not to soft. it will go right in place.

    Add the jagged washer and add the the nut. use your piece of chain to feed through sprocket in the bottom reverse positon and make the first link hit a wall to stop sprocket from turning. tighten the nut. remove chain links, put your chain on put your cover on. and your good to go.

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