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Author Topic: Snapped bolt CB400f breather cover, what to do?  (Read 459 times)

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Offline Frogger

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Snapped bolt CB400f breather cover, what to do?
« on: April 14, 2014, 11:40:42 pm »
Hi, I have recently acquired a '75 CB400f and was going to open her up and have a look at least in the top end (have rudimentarily started it with leaky carbs and seems to be running strong enough) - when undoing the breather cover, found one bolt missing and underneath was the remnants of it being snapped of in the head. Any recommendations on how or if I can extract this. I am limited on tools and mechanical experience.
Many thanks.
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Offline calj737

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Re: Snapped bolt CB400f breather cover, what to do?
« Reply #1 on: April 15, 2014, 04:30:04 am »
The easiest method with that bolt is to remove the gasket and weld another bolt end-to-head. Then you can turn the new, extended bolt.

If you don't have access to a welder, you can use a left-handed drill bit. Have to get those a quality store. Pre-soak the bolt with some penetrating oil, as the first few threads below the snap are generally the only source of corrosion. You may even be able to get some vise grips on the exposed head. (It may have been sheared from over-tightening).

Check with some mates and see if any can weld. If not, drag it to a machine shop and have them do it?
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Offline LesterPiglet

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Re: Snapped bolt CB400f breather cover, what to do?
« Reply #2 on: April 15, 2014, 04:51:10 am »
It looks to me that there is enough sticking out to grab it with vice grips.
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oldbob

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Re: Snapped bolt CB400f breather cover, what to do?
« Reply #3 on: April 15, 2014, 11:07:39 am »
My 400's PO broke off several of the screws in the clutch cover. I had some success with drilling them and then using a screw extractor.

Bob
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Offline flybox1

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Re: Snapped bolt CB400f breather cover, what to do?
« Reply #4 on: April 15, 2014, 11:17:44 am »
+1 on welding a bolt or nut right to it.   take him a few cold beers.
those screw extractors can really ufk things up if not done properly.
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Offline dave500

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Re: Snapped bolt CB400f breather cover, what to do?
« Reply #5 on: April 15, 2014, 01:45:23 pm »
gday Brendan,id try giving it a gentle rap downwards with a hammer after crc soaking for a while,then with a carefully positioned sharp punch or chisel try and drive it in the undo direction,you may find itll start turning then once you have a enough to get a decent grab with vice grips its out,never torque 6mm bolts,just nip them down and be sure any blind holes are dug out and blown clear so the bolt doesent bottom out in them.
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Offline Christo

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Re: Snapped bolt CB400f breather cover, what to do?
« Reply #6 on: April 15, 2014, 02:08:52 pm »
Hey Brendan, could you carefully grind a slot in it to accept a flat head screwdriver and then try and unscrew?
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