Help.. Broken Bottom engine casing.

Discussion in 'Motorized Bicycle General Discussion' started by Missmichelleb, Jul 25, 2010.

  1. Missmichelleb

    Missmichelleb New Member

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    Hey everyone,

    I really need some help, and i have learned so much from this site, but cant find anything pertaining to what i'm trying to fix at the moment. Oh and I should warn you, this is really the first engine i have ever worked on, so i'm not great with terms, but i do my best. Anywhoo...

    A piece of the outer casing that holds the clutch gears and the small bevel gear broke off, i believe it was caused by the half moon key that holds the small bevel gear in place came loose, this is my best guess. So i purchased a new bottom engine casing, thinking i could just change everything over. I have everything taken apart for the most part but i cannot figure out how to open the casing.. honestly i just feel alittle lost.

    I took pics of where i am at right now. Any help would be much appreciated. And if i can answer any questions that would help just let me know :)
     

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  2. corgi1

    corgi1 New Member

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    The cylinder and head have two bolts on each half
     
  3. corgi1

    corgi1 New Member

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    Is the break at the bottom of the case part we are looking at?
     
  4. Missmichelleb

    Missmichelleb New Member

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    yes.. the break is at the bottom of the casing where the circular part is. hope that makes sense. You can see it in the pics, just like a one inch piece missing.

    So i need to remove the top part, cylinder and everything, then ill be able to open the bottom casing?
     
  5. 2door

    2door Moderator
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    The broken, missing part is not in a critical area. The opening will allow dirt and grime to enter the clutch areas but it could be sealed with something. There is no compression loss or air leak into the intake at that point. Before you go to all the work of rebuilding the engine I would try sealing the broken area and riding the bike. If by some chance you have the piece that came out, it could be set back in place with a metalized epoxy such as Devcon Liquid Steel/Aluminum. That sure seems a lot simpler that tearing the engine completely apart especially if you have limited experience.
    Tom
     
  6. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I concur with 2door... do what he says! (^)
     
  7. Kevlarr

    Kevlarr New Member

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    And if you don't have the piece just use some aluminum tape to cover the hole.

    [​IMG]
     
  8. Missmichelleb

    Missmichelleb New Member

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    I dont have the missing piece and i guess i thought it was important to have a seal there. But if its not, then ill put it back together and test it out. Do you think the foil tape is strong enough or is there something else that would be better? I do have some JB Weld stuff.. just am not sure what would work best.

    Thanks for everyone's help.
     
  9. 2door

    2door Moderator
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    I'm not a big fan of JB Weld but many members swear by the stuff. For this repair it might work just fine. The trick is to get the area clean, free from any oil or grease and try building up the area where the piece is missing. You could try an old method whereby you use tape to back up the hole then fill it with the repair material of your choice. You'll need to smooth the edge where the clutch cover meets the case making it fit snuggly to seal out dirt. Wax paper between the case and cover can be used to keep the cover from being 'glued' to the case while you apply the epoxy. In all honesty the aluminum foil tape idea might work too. The idea being to keep the clutch from getting too dirty.
    There is a point that is being overlooked here and that is the loss of the woodruff (half-moon) key. Was it missing when you removed the small gear? Is the crankshaft/gear/key in good shape or is anything damaged. That key is an important item and must be installed correctly during reassembly. Good luck. Keep us posted on your progress.
    Tom
     
    #9 2door, Jul 26, 2010
    Last edited: Jul 26, 2010
  10. Missmichelleb

    Missmichelleb New Member

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    I had some JB Weld stuff that sort of works like clay. I used it to built up the area, and i did my best to smooth the area inside and where the cover touches. I think i did a pretty good job. see pics.

    I did lose the half moon key, but i bought new ones. So i have them, i did have the halfmoon key come loose on me before so i am sort of familiar with it, i know that its very important. But i think that maybe last time i re-installed it i must have not done a very good job because i'm pretty sure it was that key coming loose and getting caught up in the gears that caused this. I would really welcome any instruction or suggestions on how to install the half moon key, everything seems to be in good conditions, gears and everything.
    oh i did also buy a seal thing, i dont know what its called. I took a pic, i'm pointing to it with the pen. It looked a little worn to me, i'm not sure how hard it is to change or how important it is, but at the time i was thinking it was going to be rebuilding the whole thing.. so i thought i should just change it. Suggestions?

    Again.. thanks so much!!
     

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  11. 2door

    2door Moderator
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    Your repair looks good. It should hold but keep an eye on it too.
    That is indeed a seal. It seperates the crankcase from the atmosphere. If it looks bad and you have a new one, now is the time to replace it. You can pry it out of the case easily with a small screwdriver or similar tool. Clean the bore where the seal rests. Installing the new one just takes a little patients, a socket just a little smaller than the outside diameter of the seal. Apply a little oil, your engine oil is okay to use, to the inner lip of the seal and the end of the crankshaft and carefully center the seal on the crank with the open side facing in. Push it in as far as you can with your fingers, keeping it centered in the bore then tap it all the way down with the socket and light taps with a hammer until it is flush with the case. I should have said earlier to use a deep well socket so you don't damage the end of the crankshaft. Good luck. You should be good to go.
    Tom
     
  12. Missmichelleb

    Missmichelleb New Member

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    Thank you Tom.. i'm going to change out that seal when i get home, and put everything back together. Do you have any suggestions for the best way to install the halfmoon key? I want to get it right this time, so the little bugger doesnt come out again. :)
     
  13. 2door

    2door Moderator
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    The woodruff key should fit fairly snug in the groove (keyway) provided in the crankshaft. If it doesn't you might consider replacing it. If the keyway is worn then we have a more serious problem. I'm sure someone is going to suggest JB Weld for this fix too but as I said before, I'm not a JB user. There are epoxy based products with much more strength that I would use to hold the key tight. Devcon makes an industrial metal repair material, Liquid Steel, that would assure the key would stay. Let's determine first how well the key fits the keyways in the crankshaft and gear. If you find the fit good, no slop, you can try a small dab of superglue to hold it in place while you install the gear. If the key rattles around in the grooves get back to us for more detailed help.
    Tom
     
  14. Al.Fisherman

    Al.Fisherman New Member

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    Not quite finished, but here you go...

    http://s982.photobucket.com/albums/ae309/Ron-Becker/Chinese HT breakdown/

    Super glue the woodruff key in place, let dry, and slide the part over the shaft. This method is almost needed when replacing the magnet in the magneto. 2Door...I didn't read your whole post..like minds and yes JB Wield for the most part is c.r.a.p. Although there are applications where it is useful, and I keep some at the house for those such times.
     
    #14 Al.Fisherman, Jul 26, 2010
    Last edited: Jul 26, 2010
  15. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    JB Weld is the shizziola when used correctly and in the correct application. I have model airplane engines I have fixed broken crankcases on and then run for years.

    Don't use it to put the woodruff key in though.
     
    #15 Bikeguy Joe, Jul 26, 2010
    Last edited: Jul 27, 2010
  16. BarelyAWake

    BarelyAWake New Member

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    o.o

    I'm soooo gonna burn fer this, but... I CAN'T HALP MESELF >.<

    [​IMG]


    ZOMGBBQCHICKINSONASTICK THEY'RE GETTIN' TEH TORCHES OUT [​IMG]

    /fleez in terror




    [​IMG]
     
  17. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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  18. BarelyAWake

    BarelyAWake New Member

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    I know a mod can ban a mod... DON'T DO EEET JOE, please step away from the button kfnx :D

    I have cake *nods*
     
  19. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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  20. BarelyAWake

    BarelyAWake New Member

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    *BAW gives the sacrificial pie and all is well in modland again*

    o_O Wow... I've set an epic example by spammin' this poor guy's thread eh? Sorry 'bout that all...

    I've had WAAAY too much cawfee this morn' :oops:
     

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