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Help Please! Snapped a bolt!

  • Thread starter Thread starter KnuckleBuster
  • Start date Start date
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KnuckleBuster

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I was putting the engine back together today after replacing a cracked piston in my '78 GS1000 when one of the "hardened" bolts that holds the exhaust camshaft in the head snapped off pretty much level with the surface of the head. It is one of the bolts that goes through the locating pins, so when I say level, that means recessed into the head about 1/8" with about 1/16" all the way around it. How the heck can I get the rest of the bolt out of the head? I'd hate to take it all apart again and buy a whole new gasket set, but if I must, I must.

My father's been helping me with this and he thinks the bolts may have stretched. It seems as though they bottom out before really becoming tight against the blocks that hold the cams. Any thoughts on this?

Thanks so much for any help. I was on the verge of tears this afternoon - the darned bike only has 18,000 miles on it. This broken bolt has really got me down.

Thanks,
Jay
 
If it bottomed out you've got a tough one on your hands. I had the same thing happen with an exhaust bolt. Initially I drilled and tapped the broken bolt to accept a smaller diameter bolt. Recently I drilled and tapped that to accept the right size bolt. Needless to say you have to be accurate with the drill. You may not even have room to drill depending on which bearing is involved. An easy out isn't going to do you much good either if it bottomed out. Then if you bust that off you're really screwed. Drilling and tapping is probably your best bet if you can get a drill in the space you have to work with.
 
Bolts DO stretch, but not usually so much that they will bottom out and break. Normally, they stretch under torque, and when you reach the tension limit, the metal breaks.

As to your situation......you can try to centre-drill the bolt and back it out with an Easy-out, or similar tool (NEVER use the ones with a threaded body....use only the ones with a squared shaft and sharpened edge, and ONLY use a recognized professional brand)

That idea works....sometimes....and the drilling is best done on a drill press to get the most accuracy.

Generally, you consider whether the bolt was put in dry or with a lubricant.
If it was lubricated, this method may work, and there is always the chance of breaking the removal tool. If if was put in dry, the odds are reversed... you will probably break the tool.

BTW.....if you break the removal tool, you are best to quit all efforts, pick up your work and go to a machine shop. A standard HSS (high-speed steel) drill bit will not cut through the hardened tool steel, and if the bit you are using slips off to the side you will cause damage...quite possibly irreversible damage.

Other than that, you still need a drill press, and you centre-drill the broken part, then use a bit with a diameter that matches the body of the threaded bolt. The body is the part under the threads.

Then you may be able to use a tap to clean the original threads. Touchy, as the start point of the tap may not exactly match your original threads.

Still not working? Two choices

Tap it slightly oversize, and use the next size bolt to fit.

Buy a thread insert kit. Follow the instructions. Basically, these are: Drill out the broken part completely and screw in the insert. Reassemble as per normal.

Use a torque wrench.

Always, always, always, lubricate the threads before assembly. Use light oil, or, if loosening due to vibration is a concern, use a thread locker, such as Loctite. Be sure you use the correct one. It acts as a lubricant, and a thread sealer/locker, and keeps the bolt in place once the chemical sets up.


Lubricating the threads is the ONLY way to get a dependably accurate torque reading.
 
my standard response, get it tig welded out. i personally have gotten bolts broken down as far as one and a half inches in a 3/8 "dia hole all you do is build up a little T on the end and put vise grips, cresent wrench, pliars ,whatever to it and back it out ,i do this on a daily basis,even machine shops that could do the job right in a mill or edm send it to me beacause it is cheeper, faster,better than they could do it inhouse. are you in the toledo area? i could show ya. Mark
 
I have broken 2 or 3 of these. I each case I was able to drill a small hole in them and back them out 'easily' with with an an Easy-out. In every case, as I was drilling them, the broken bolt twisted in a little further, which tells me mine didn't bottom out and break. I always used a torque wrench for assembly and the threads are lubricated. I think these bolts are just weak.
 
Going with an easy out works sometimes. Good advice on the type of easy out (square type). I also have a set of left handed drill bits that are just for my easy outs. About half of the time they get the bolt out all by themselves.
 
Great News! I was able to get the bolt out. It cost me the price of a right angle drill from Sears, but the sucker is out. My father drilled a small hole down through the center of the bolt and used an easy out to extract the bolt. Both the reversed drill bit and the easy out were from MAC tools that a coworker lent my father for the evening.

Does anyone know what the torque Specs are for these bolts. My Clymer manual just says, "tighten all bolts evenly," but doesn't give a torque spec.

Thanks for all the help,
Jay
 
If these are the bolts for the caps (also called the cam holder) the torque for a 1980 GS750 is 7 lbs-ft or 1.0 kg-m. I would think the 1100 series would be the same.
 
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