best way to remove broken head bolt?

[lbo]

Doing my first BBK upgrade on my Kymco Super 9. Everything was going well, got beyond the wrist pin clip patience and everything. Setting the rings was a little challenging too but she turned over without a squeak.

Went to tighten the head bolts and wanted to make sure I torqued them down properly. I looked up the spec, 14-16N-m.


Noticed my wrench is only in Foot Pounds so I looked up the conversion and set it to 12.





Keep in mind I didn't have a 10mm 1/4" socket in 10mm, so I used an adapter. Then I used another adapter to fit the torque wrench. Not sure if this threw off the precision here;




Anyway I was going at it, using a cross pattern until they got more tight. Switched it up on another tightened bolt hoping to hear the wrench click.


Instead I heard the bolt snap;



Needless to say with this happening a short time ago I am a little bummed out and in shock. I understand this is just a little set back and part of doing a build for the first time, just hoping there is a relative easy way to get it out. There should be a way to drill some of it so I can then twist is back out right? And if so where I can I find replacement bolts.

Thanks in advance.

[90GTVert]

Remove the rest of the cylinder first and hope there's something left sticking out. If so, use vice grips to unscrew it. If not you'll need LH drill bits or a bolt extractor most likely.

[tango]

Bearing in mind that the bolts could very well be of poor quality, head bolts are rarely a single-shot procedure. Some manufacturers will tell you torque to A Nm wait a few minutes then torque it to B Nm or to a particular angle. Then wait a while again and talk to another angle and so on. This allows time for the bolt to stretch slowly. The manuals I am seeing don't specify any such procedure, but I would err on the side of caution. Torque to the lower figure first, then allow time for the bolt to stretch and then torque to the upper figure.

As for removing the bolt, my pal and yours, 90GTVert has a video:



My official tools tore (and likely that of 49ccscoot.com as well) has the extractor tool for a nice price (<$10):

www.harborfreight.com/13-piece-left-hand-drill-bit-set-95146.html

[lbo]

Thanks for the feedback so far everyone and the video is great tango, thanks 90. What a great resource of info you have provided to this site btw.

I also understand it doesn't help to use this 150ft/lb wrench for a deliate procedure, would still think it's accuratish. Maybe not but could see the calibration being off and my poor judgement being a factor here. Now, in hindsight.

I thought about something sticking out, looks as though it snapped where the thread starts. I guess it depends on how far down the case the threads start. The corroded part of the bolt is what is exposed to the elements so there is a good few inched of protected bolt...... the base of the jug slides down about far. Or so I am thinking.


I need to look up an easy out, and get the axis aligned properly.

[jmkjr72]

no that torque wrench will not be close at low settings
get your self a smaller one that is rated in inch lbs
i persoanly like screw in studs over bolts

[tango]

Another thing that some manufacturers will tell you (which the manuals I am seeing doesn't say) is to torque the bolts with or without lubricant under the bolt-head. I doubt this was an issue though since the bolt broke off at the thread, so low down on the shaft. Honestly, I'm thinking poor metallurgy here.

[lbo]

It looks like a semi clean break, at least accessible.



I put a few drops of oil on it to let that sit in today.

I have these;


Looks like the smallest will work. I need to pick up a spring loaded center punch and make sure I have an appropriate drill bit. Lastly I will need to pick up some replacement bolts. I have a broken off CVT bolt that is lodged in the case too, I will use that one as a practice run.

<crosses fingers>

[jmkjr72]

i have the same set of easy outs at the office
i like to start with a drill bit that my be too small and work my way up one size at a time
and a nice gently tap with a dead blow helps seat them and bring the busted bolt out

[lbo]

Thanks, I am going to try it out here in a few minutes.

On a side note I can't find a replacement bolt anywhere; 7mm 1.0X100mm

[1quikvento]

If the threaded part didnt bottom out in the case, sometimes you can tap on one side of the threads in off direction and it start to spin out easily enough for you to grab onto with channel locks or vise grips. I found a site recently that has your size bolt. I think theyre studs, Which you should change to anyway. I gotta find its name. Theyre outta san francisco and its a weird site... hold tight..

[1quikvento]

look on treatland.tv- I did a quick search so i didnt lead you in a wrong direction and they got all kinds of m7 stuff. they were like 3.00 or so I believe. I had to do a m7 heli coil in that same exact stud spot on my case and I still have the kit with 10 or so coils left. kits are expensive. Lemme know if the project goes south and I can send you wat u need.

[lbo]

Thanks for the help. I found a Kymco parts place that has them, getting 4. Not in stock and might take 3-5 days, thats OK because I am waiting on other stuff and have some go fast goodies to install in the mean time. I needed a couple other things including teh bolds for the CVT cover.

I have practiced on the CVT busted bolts (have 3 busted bolts, 3 working with helicoils, 3 original) and didn't make much progress. I was able to center punch and drill ok, the extractor doesn't want to grab it. I am going with a bigger drill bit and letting my battery charge in the mean time. Glad I have 3 bolts to test out before tackling that head bolt. I will try to move it around and see if it unscrews with some taps.

[bigjeff]

Rust and neglect is a scooter's biggest enemy. What he said about tapping the bolt before extraction is critical. Loosens up corrosion. Give it a decent whack with a dead blow before trying to turen it out. You may want to hit it with some penetrate and let it soak over night too.

[jmkjr72]

once you get it in there give it a few wacks with the hammer to help the ez out grab and loosens them up
i like an oil called freeze off www.autobarn.net/freeze-off-super-penetrant.html

good luck with getting the bolts i have had horrid luck getting the right stuff from kymco and have even been there when the dealer called the order in and personaly confirmed the pn was the right pn from a few diffrent parts manuals

[lbo]

Thanks everyone for the help!



I was a little nervous since my practice bolt didn't cooperate, took my time got proper tools and reviewed this thread a few times. Now just waiting on the replacement bolts.