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Discussion Starter · #1 ·
Hi all,

Sorry for the long ramble here, but I need some help/advice before I mess something up big time..

In the middle of valve clearance adjustment on my 2016 ER-6F, no big problems..

Come to put the cam holders back on and all going swimmingly until it comes to torqueing up (to 12Nm) after gradually tightening them down..

Following the service manual tightening sequence I get to bolt 6..

It's tightening, but taking longer than the others with no force seeming to come onto it.. I ease it back out and check it, run it in by hand and threads seem fine so proceed to torque it again.. I go in stages, getting it to 10Nm, keep going gently on it and then "ping!"..

"Bother!" I say to myself and nearly start to cry as I've only gone and broken the bolt...

I compose myself and come back to it, ease it out and luckily the broken end is still being held on by a thread and comes out with the head of the bolt.. "Result!" I say to myself..

Hmmm, why would the bolt break when I'm no-where near the torque? (it really wasn't tight at all).. I take one of the later bolts in the sequence and begin to tighten it down into hole 6 to see if it's just the bolt, but I can't seem to get it to tighten (I'm obviously being very cautious!) and don't want to risk breaking another bolt and getting it stuck in there!

So...

What to do now?

I've run a cotton bud with a bit of grease into the hole and no swarf came out so I don't think the threads are done (or are they??)

I've hand run another bolt down into there and it feels fine and easily gets hand tight..

Could the bolts be weak somehow?? (55k on the engine) and simply getting a new set of bolts will fix the problem??

Or do I need to stick a helicoil in the hole? (Something I really don't want to do unless absolutely necessary as I'll probably need to drop the engine as it's the hole in the front left corner so getting to it with a drillbit isn't really possible with it in the frame - unless I can just run the tap through without the drill bit first??)

Anyone else been here - thoughts/help??

Cheers...

139307


139308
 

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If the bolt broke that thread is 100% fine. The bolts fatigue quite a lot, technically cam and engine studs aren't supposed to be reused as they stretch the first time they are tightened down. Usually it's fine to reuse them but you just encountered the scenario when it isn't. Nothing to stress about really, just replace them. If you want piece of mind replace them all. They are M6x45mm and they cost about £1.50 each from OEM kawasaki. You need 12 in total (i'm sure you noticed haha). I've had the same happen to clutch bolts on an old yammie 2/4 bolts broke well before I reached the 12Nm torque, on of them immediately after going hand tight just sheared like butter... Fortunately those were just standard M6x25 hex head so I literally just replaced them with a pair of random ones I had at home, 0 problems 10k miles down the line before I got rid of it. That said, in the head I'd not go putting in random bolts, kawi originals are cheap enough.

Edit: technicalities and actually upon closer inspection of the bolt it's obvious that was the case, you can see right where it cracked the threads are stretched, I'd inspect the other bolts just in case but if they're up to torque specs then they've handled their jobs and should be fine.
 

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Discussion Starter · #3 ·
If the bolt broke that thread is 100% fine. The bolts fatigue quite a lot, technically cam and engine studs aren't supposed to be reused as they stretch the first time they are tightened down. Usually it's fine to reuse them but you just encountered the scenario when it isn't. Nothing to stress about really, just replace them. If you want piece of mind replace them all. They are M6x45mm and they cost about £1.50 each from OEM kawasaki. You need 12 in total (i'm sure you noticed haha). I've had the same happen to clutch bolts on an old yammie 2/4 bolts broke well before I reached the 12Nm torque, on of them immediately after going hand tight just sheared like butter... Fortunately those were just standard M6x25 hex head so I literally just replaced them with a pair of random ones I had at home, 0 problems 10k miles down the line before I got rid of it. That said, in the head I'd not go putting in random bolts, kawi originals are cheap enough.

Edit: technicalities and actually upon closer inspection of the bolt it's obvious that was the case, you can see right where it cracked the threads are stretched, I'd inspect the other bolts just in case but if they're up to torque specs then they've handled their jobs and should be fine.

Thanks man - I just needed some reassurance that that's what it is.. I have a history of seized bolts and damaged threads on this bike (ridden all year round) and really didn't want to disappear down a rabbit hole on this one.. Bolt broke so easily was the thing that freaked me out - 10Nm!! Totally felt like the thread going, but you're right - if the bolt broke then the threads must be fine (I hope)
 

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Thanks man - I just needed some reassurance that that's what it is.. I have a history of seized bolts and damaged threads on this bike (ridden all year round) and really didn't want to disappear down a rabbit hole on this one.. Bolt broke so easily was the thing that freaked me out - 10Nm!! Totally felt like the thread going, but you're right - if the bolt broke then the threads must be fine (I hope)
Well you said you had no issues putting in another bolt and there was no metal flakes so I highly doubt it's a matter of it getting stuck whilst cross threaded and then snapping.
 

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Discussion Starter · #5 ·
Well you said you had no issues putting in another bolt and there was no metal flakes so I highly doubt it's a matter of it getting stuck whilst cross threaded and then snapping.
Yeah - I can easily hand turn a bolt all the way to the bottom.. New set of bolts it is and give Cradley some more of my hard earned :ROFLMAO:
 

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Sounds like the Bolt may have Hydrauliced in the hole, What's all that Grey looking residue around the hole and on the cam lobes, Looks like Moly Grease..
 

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Discussion Starter · #7 · (Edited)
Sounds like the Bolt may have Hydrauliced in the hole, What's all that Grey looking residue around the hole and on the cam lobes, Looks like Moly Grease..
I only got the moly grease around the hole when i fished in there for any swarf.. There is moly grease on the cam lobes yes - as per service manual (moly on cams, moly/oil mix on journals and blocks).. Still for an M6 bolt to shear at 11Nm shows fatigue in the bolt surely? (Or am I missing something do you think?) (I did not grease the bolts on insert..)
 

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Yeah - I can easily hand turn a bolt all the way to the bottom.. New set of bolts it is and give Cradley some more of my hard earned :ROFLMAO:
I find Cradley to be pretty reasonable, use them for all low cost OEM parts.
 

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I only got the moly grease around the hole when i fished in there for any swarf.. There is moly grease on the cam lobes yes - as per service manual (moly on cams, moly/oil mix on journals and blocks).. Still for an M6 bolt to shear at 11Nm shows fatigue in the bolt surely? (Or am I missing something do you think?) (I did not grease the bolts on insert..)
In that case I would agree with Metal Fatigue but a 16 Plate with 55K seems more like sub standard material at production or commonly refered to as a Bad Batch ;)
Personally for peace of mind I'd replace all of them as this one was OK until this time round so how many are sitting there ready to let go :(
 

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Discussion Starter · #10 ·
New bolts arrived and job done.. Although I was shaking tightening them up.. They don’t “bite” and then tighten like normal bolts it seems - it’s like they stretch, took quite a bit of turning to get from 11Nm to 12Nm with me bricking it the whole way.. Thanks all!!
 
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