Damn't I broke a bolt

"450X_FTW" (mistermic) 05/04/2016 at 09:36 • Filed to: None

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Was converting my dirt bike to supermoto yesterday evening, I took the chain guard off and the bolt holding the front sprocket to the transmission output shaft fell out. At first I thought I did not tighten it well enough months ago, but then I realized the bolt was broken mid thread. Very lucky no additional damage was done considering I just did a 40 mile race on Sunday and a 60 mile trail loop the previous weekend.

My friend out west who builds race bikes said they replace that bolt every time they replace the sprockets, I didn’t know that, and this is my 3rd set of sprockets. Likely it was torqued to yield and failed, but I’d like to think that it broke as a result of too much engine torque from my recent motor rebuild I just completed.

Either way, extractor kit is on order.

Hammerdown > 450X_FTW 05/04/2016 at 10:06

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That sucks. Looks like it broke off way in there. What’s the torque spec on that bolt? How bad do you think it will be to get it out?

450X_FTW > Hammerdown 05/04/2016 at 10:13

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Off the top of my head I think it’s 25 ft lbs. It broke off right where the threads stop on the female end. I’m planning to lean the bike on it’s side and fill that hole full of PB blaster, let it eat away at any possible corrosion holding it in, making it easier to remove. Hoping a center punch, drill and extractor will make it easier, Just nervous about it is all. If I can’t get it out, then it’s going to be a HUGE PITA to remove. #2 in the schematic.

Hammerdown > 450X_FTW 05/04/2016 at 10:15

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yea that looks rough. Left handed drill bits are your friend.

450X_FTW > Hammerdown 05/04/2016 at 10:16

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Yep just ordered a set, will arrive tomorrow with extractor bits and the center punch

Meatcoma > Hammerdown 05/04/2016 at 10:26

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When I replaced the exhaust manifolds on my truck, I used left handed drill bits and damn if they aren’t your best friend.

It’s odd how many people I talk to that are somewhat mechanically inclined that look at you like you are crazy when you mention them. I mean they actually think you are fuckin with em.

brianbrannon > 450X_FTW 05/04/2016 at 11:25

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It should come out pretty easily if you didn’t cross thread it. Try two picks and a little pressure or a drill on reverse and a flat head screwdriver bit

Luc - The Acadian Oppo > Meatcoma 05/04/2016 at 11:42

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I had the hardest fucking time finding left hand bits. Everyone thought I was fucking nuts! “I’ve been selling bits for 30 years and you have no idea what you are talking about” I ended it drilling the bolt out completely and tapping the hole bigger. If I would of hand left handed bits I would’ve solved the problem in 10 seconds instead it took me 4 days of swearing.

http://oppositelock.kinja.com/help-im-desper…

Meatcoma > Luc - The Acadian Oppo 05/04/2016 at 11:55

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Ouch. Yea I drilled a hole in one, broke an extractor in it because apparently I used too small of one and had to drill a hole beside that one which dislodged the broken extractor, allowing me to drill a bigger hole through the two previous holes and then use 2 size bigger extractor. That was before I bought a set of left handed bits and removed 4 other ones super easy..

Here is a pic of the bolt with 2 holes drilled in it.

And one with the extractor finally in it.

and how close it actually was lol.

And... Left handed Drill bit to the rescue!

BobintheMtns > 450X_FTW 05/04/2016 at 12:22

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The chain will hold the sprocket in place, I wouldn’t worry about it.. and anyway, the bike will be lighter without the bolt...

450X_FTW > brianbrannon 05/04/2016 at 12:47

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The other half of the bolt is deep in there. Not cross threaded thankfully. There’s nothing to grab ahold of with the flathead