Advice on how to remove broken bolt

Discussion in 'Spare Parts, Tools & Product Developement' started by IINoxiousII, Apr 20, 2012.

  1. IINoxiousII

    IINoxiousII Member

    Hey guys,
    I'm new to this so forgive me if I am off on my terminology. I ordered a centrifugal clutch recently. Everything was going great. I had it installed and it was working perfect. I noticed at high RPMs that there was slipping, I think, with the clutch pads, so I disassembled the clutch, tightened the clutch and as I was re-assembling the centrifugal gear I broke off the main bolt that holds the centrifugal gear into place into the crankshaft..... :whistling: I took off the centrifugal gear and the bolt is broken flush with the crankshaft. I can't get it out and I don't think I will be able to bore it out. Hopefully I'm wrong.
    I was wondering what can I do? Your help and advice is greatly appreciated.

    I attached a pic of what I'm working with here.
    Thanks guys!
    Kind regards
     

    Attached Files:


  2. Al.Fisherman

    Al.Fisherman Active Member

    If that bolt was supplied with the clutch kit, it shouldn't be too much of a problem. The hardware supplied is c**p just soft junk...that the good side. You will need to take a center punch, and punch the end of the broken bolt as center as you can. Then start out with a small drill bit 1/16" and drill as far as you can go. (I'll measure for you how deep the hole is and report). Then step up to a larger drill bit. Keep going until the hole is ALMOST to the threads. Then remove the broken bolt with a easy out/screw extractor. When replacing the bolt use a metric grade 8.8. It NEVER amazes me the amount of riders that depend on the junk hardware supplied with these kits.....

    Update
    The hole in the crankshaft is 1/2" deep. When replacing the bolt, do not get one that will bottom out in the crankshaft. Thinking about it I'd see if a stud and then a locking nut, to hold the clutch on will work. If so, I think that would be a better set up. Keep the drill as straight as you can when drilling. Picture of stud and nut. Of course the stud has to be cut to length, and the threads are 8 X 1.0
     

    Attached Files:

    Last edited: Apr 20, 2012
  3. IINoxiousII

    IINoxiousII Member

    Wow, thanks Al!
    A lot more than I was hoping for. Definitely a newbie move on my part over torquing the cruddy hardware I was provided. I definitely will up grade all shoddy pieces that will be under more stress than they can hold. Your prompt reply is diligent and greatly appreciated!
    I hope my application is as good as your explanation. I will keep you updated.
    KR,
    P
     
  4. Al.Fisherman

    Al.Fisherman Active Member

    Here are some tips on installing a HT engine.
     
  5. Fabian

    Fabian Well-Known Member

    If you are installing a centrifugal clutch, there is a necessary modification for long term reliability.

    Send me a PM and i'll send you the web link.
     
  6. Fabian

    Fabian Well-Known Member

    From past experience, a broken clutch bolt is usually caused by the bolt bottoming out at the end of the crankshaft recess.
    I had to grind away the last three threads from the bolt to enable correct clamping pressure.
    An easy test: cover the last 10mm of the bolt with paint; let it dry and install the centrifugal clutch.
    Remove the bolt and see if any paint has been removed from the end of the bolt or the last few bolt threads.
     
  7. steveonbroadway

    steveonbroadway New Member

    I take out broken studs all day at work, "auto machine shop" you really only have to get the tip of easy out say about 4 mm or so.. hammer it in your drilled hole.. dont break off easy out in it... you have to FEEL it...:)
     
  8. IINoxiousII

    IINoxiousII Member

    Thanks guys,
    I feel like this is a title bout for the main event tomorrow. (That's when I have time to work on it lol). Good thing I have you all in my corner! All I need is the theme song from Rocky. Will keep you guys posted
     
  9. steveonbroadway

    steveonbroadway New Member

    If you like I can send link to drill bits I use they are made by Irwin double sides 1/8 and very Sharp.
     
  10. Al.Fisherman

    Al.Fisherman Active Member

    There are at times a "left handed" drill bit will work.
     
  11. IINoxiousII

    IINoxiousII Member

    So far no luck. I am going the easy out route since the left handed drill bit didn't grab the bolt enough to twist it out. However, these Ryobi easy out bits seem so brittle. It feels like it is going to snap off inside when I try and torque it manually. I'm afraid to use a drill and have it snap off. I'll keep trying. Today, I am going to try heating and cooling a few times to see if I can ease it out. Thanks for the help so far.
    P
     
  12. Lunardog

    Lunardog Member

    In the interim when your not working on it put a few drops of penetrating oil or WD-40 on the seam between the bolt and the shaft with the engine on it's side so gravity will draw the oil downward.It may not be visable to the eye but it will seep down along the threads with time and may assist with the extraction. Letting it sit overnight might be a good idea.
     
  13. Al.Fisherman

    Al.Fisherman Active Member

    That is why I recommend to step up the drill sizes. Enlarge the hole as far as you can without getting into the case threads. This will enable you to use a larger screw extractor.
     
  14. steveonbroadway

    steveonbroadway New Member

  15. IINoxiousII

    IINoxiousII Member

    I enlarged it to as far as I can go. Anymore and I am afraid I might be eating away at the threads. I had used loctite on the bolt that had broken off. I'm hoping by heating it I can release its hold.
     
  16. Al.Fisherman

    Al.Fisherman Active Member

    Ummm, I don't think you ever mentioned using locktite on the bolt. Now you may need heat. Heat it up, and spray some PB Blaster (always good to have a can around the house), let cool and repeat. Then heat and go with the screw extractor. Do NOT heat with the screw extractor installed in the broken bolt. With heat, you will need to replace the seal, which isn't a problem.

    I would remove the clutch gear, and remove the seal before heating it.
     
    Last edited: Apr 24, 2012
  17. IINoxiousII

    IINoxiousII Member

    OK! I am finally finished. Here's the skinny on what happened and why it took so long... The bolt would not budge. I tried heating it and spraying PB blaster on it, but I think it was just holding on too tight. The easy out would have worked, but I think I may have drilled too large a hole and when I was trying to screw it out with the easy out, there just wasn't enough bolt left to prevent any expansion so it was just digging into the threads. (My humble hypothesis). What I ended up doing was drilling practically all the way to the threads (The center punch idea came in handy bc I was able to get it centered practically perfectly). A friend of mine is a dentist so I asked him the other day if he had any used tools (The hardened steel tools with a hook on either end). Fortunately he had a few that he gave to me and they did the trick. I was able to pick out the metal from in between the threads and the loctite residue that was left over. Worked like a charm. Afterwards I re-assembled and took the bike out for a long stroll lol! Good to have her back running again. Thanks again for all your help guys. I hope this thread can help out others too.
    Kind regards,
    P
     
  18. Al.Fisherman

    Al.Fisherman Active Member

    Good for you......:idea:
     
  19. DeathProof

    DeathProof Member

    another successful story case closed!
     
  20. V 35

    V 35 Member

    I've had good luck ' bunging ' broken bolts. Center punch outer edge, than take a long, sharp punch, and a light hammer, you might want to drill a little into the punch marks, just drill enough, aprox. 1 mm for tool to grip. with a few deft taps, the stub spins out. when a bolt breaks, tension against threads relaxes, and bolt spins easy. When a bolt breaks because of a jammed thread, the stub is not going anywhere, drilling the center takes pressure off threads. The Unicorn style easy outs tend to snap flush, I bought name brand ones at a lumber store, and they snapped flush, ruining expensive castings.
     
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