Breaking head bolts every time

I will never reuse head bolts again

/me thinks that it's a good decision... especially a snapped head bolt could turn a 1st grader operation into a machinist nightmare !

I don't mine changing cam caps bolts, head bolts and exhaust stud each time i part my engine... just buy a good quantity (50 +) and your are good for lifetime

best regards,
laurent

EDIT:

just buy a good quantity (50 +)

... yeah i know I've been diagnosed with a breakophobia syndrome :laugh: ... fear of anything breaking again (from badly past nightmares!!) !! I change studs, bolts when i see even a small rust dot on it !

There's also a price issue to consider... a new set of studs costs almost as much as the replacement parts engine I bought!

Also, apart from these head bolts, I'd be more afraid of stripping threads out of the aluminum engine than breaking a bolt.

There's also a price issue to consider... a new set of studs costs almost as much as the replacement parts engine I bought!

This is why we need a group buy section on this site !! Imagine a set of stud at 20 $ each ! Higher the quantities lower the price!

I have been following this thread and have wondered why those bolts in the second picture are tapered like they are? I would be afraid to put much torque at all on those bolts!

Hi.
New to the forum and just wanted to say to "Staniel" that someone else is indeed having the same problems with the cylinder head bolts shearing, so you are not alone. My bike is a 1982 z750 ltd but same bolts and the same problem.
Interesting that your story is exactly like mine, I even had the spare bolts from another engine like you!
Also, like you, I stopped tightening the bolts when things started to "feel wrong". Less than 15ft lb sometimes.
Thanks for posting with the part number as that was very useful. I have ordered new ones but think the bolts may resemble the one you cracked your head with, as they seem to have been superseded by non "necked in" bolts.
Thanks also for all the pics, very useful.
Hope this reaches you 2 years after your original post!
Gary.

Thank you for posting here! You reminded me to post an update!

Beware OEM head bolts for small engine KZs!

I heard from a fellow at a Kawasaki dealer that the OEM bolts manufactured over a certain period of time are indeed not up to snuff. He said he's had this problem and has heard of it from others. He might be a BSer, but it felt good to have someone confirm the problem exists.

Also, GPz550D1, the reason the bolts are tapered is that they're meant to neck out at torque. The bolts are supposed to be single-use and their taper ensures that.

Thanks for your reply. Not sure why Kawasaki don't trust us with these 2 bolts. Every other bolt
on the bike relies on us using torque settings and/or common sense, but with these 2 we need
a fail-safe!
I am wondering why your head cracked using the stainless bolt, as I am sure you would have used
the same torque settings. A puzzle indeed! When my new bolts arrive in a couple of days I will let you know
what they look like.
Did you establish that 22ft Lb is the correct setting? In your original post someone suggested this
might be wrong. They suggested about 8ft Lb but I believe they may have been thinking of the
external type bolts that are much smaller. That type were fitted to my gpz550.
Gary

From what this dude says, it's not that they don't trust us - it's that they effed up.

I do get it about why these are the way they are. A lot of heat changes happen in there, and this is a critical piece, which runs into some really thin-wall aluminum.

My recommendation is to do what I do:

Use the OEM head bolts. I set my torque wrench way low, turn it 'til it pops. Turn the wrench up a couple inch pounds, go it again. You'll get a sense of how many more degrees you can turn the wrench before it pops since the last increase. For me it's maybe 10 degrees. At some point around 75% spec, you'll turn the wrench to 15 degrees, you'll get suspicious, turn it to 20 and panic. That's when you stop. You leave them in there at below spec torque and you finish the job.

Be sure to put some black permatex on the oval o-rings in the oil channels at the head gasket level in addition to what the manual specifies (which I believe is in the back only, where the cam chain tensioner pushes). These things are why I've had to do my head gasket so many times.

I did this last time, just like I wrote here, and I have not sprung a leak (at least from the top end).

DON'T USE STRUCTURAL STAINLESS BOLTS. My guess is that SS behaves differently with heat. In fact I know this to be true from welding. It doesn't conduct heat well, and it warps a LOT locally when cooling. The OEM head bolts are designed for their job, which surely includes dealing with some serious temperature changes.

Like I said - ignore spec torque. You might get up to 19 or so. The 8ft-lbs is almost certainly not about head bolts. That's extremely low.

Thanks for that additional info. Makes good sense what you have said about the Stainless bolts.
The bolts I have ordered are OE so should be fine.
I learned a couple more things today whilst scouring the internet. First thing is to not over-tighten cam caps
as this reduces valve clearances significantly and can also damage the caps and bearing surfaces. I usually
over-tighten everything!!
The other thing is the position of cam lobes when checking clearances. My manual (Haines) just says check
the ones pointing away from the followers but it seems that I should be checking the ones that are almost
horizontal and pointing forwards for exhaust and backwards for inlet.
What are your thoughts on this?

Also, new head bolts every time. Definitely single-use. Which is a major drag.

I wish someone had given me advice like that about the cams. I wrote a post about my second top end breakdown here, and I wrote something like that I turn the crankshaft until the cams "settle" with a snap. Then I measure them. As far as I know this doesn't work at all and my measurements are all over the place.

So basically you measure while the cams are facing outward? Awesome.

We're totally off topic.

Yes you are right, off topic!
Will post again when new bolts arrive.
Thanks again for your help.

lol, that is funny, I broke that same bolt in my 750 last year while I was taking the valve cover off.