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Breaking head bolts every time 13 May 2011 22:41 #450823

  • elfmagic17
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Kenny Hicks
74 Honda CB550
75 Honda CB360 (runs and rides good but not a show bike)
77 KZ650B1 (Runs Great, but needs painted and a little work.)

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Last edit: by elfmagic17. Reason: Add specs

Breaking head bolts every time 13 May 2011 23:12 #450828

  • staniel
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It's helpful to hear that the torque specs are wrong. I'll go up to 18 or so with the ones I have on the way in the mail.

Is it madness to torque the head nuts to 30? They seem to hold up to it pretty well...
1983 KZ750 L3 with 4-1 Kerker pipe and pods
1983 KZ750 L3 parts bike

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Breaking head bolts every time 13 May 2011 23:32 #450829

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Sounds like two passes for the nuts, 18 lb ft first pass, 29 lb ft second pass in sequence both torque settings, may be a good idea to recheck the 29 after a couple of warm-up and cool-down cycles so they don't loosen. Don't forget on the bolts, your going into aluminum, it pulls threads out easier then steel or iron, think i'd stay around 15 lb ft or a little less.
Kenny Hicks
74 Honda CB550
75 Honda CB360 (runs and rides good but not a show bike)
77 KZ650B1 (Runs Great, but needs painted and a little work.)

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Breaking head bolts every time 14 May 2011 02:47 #450869

  • wireman
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tinlizzie37 wrote: I would never replace any of the bolts with stainless. Most stainless steel is much softer than carbon steel ones. That's probably why they broke off. You can see the stretch that caused it. Bob

are we going there again? theres not a hardened bolt anywhere on these bikes from the factory,even the main cap bolts on a 900/1000 are like a grade 2 bolt! :woohoo:
posting from deep under a non-descript barn in an undisclosed location southwest of Omaha.

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Breaking head bolts every time 14 May 2011 08:47 #450893

  • mark1122
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staniel wrote: It's helpful to hear that the torque specs are wrong. I'll go up to 18 or so with the ones I have on the way in the mail.

Is it madness to torque the head nuts to 30? They seem to hold up to it pretty well...


i would stick to the specs for the nuts. 29 is not too much for them. i have APE heavy duty studs in my KZ1200, as do all guys who biuld big motors. they are speced at 42 ft lbs. and they do not pull out of the aluminum cases.
if u go light on them u may experiance head leaks.
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.

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Breaking head bolts every time 14 May 2011 09:35 #450898

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mark1122 wrote:

staniel wrote: It's helpful to hear that the torque specs are wrong. I'll go up to 18 or so with the ones I have on the way in the mail.

Is it madness to torque the head nuts to 30? They seem to hold up to it pretty well...


i would stick to the specs for the nuts. 29 is not too much for them. i have APE heavy duty studs in my KZ1200, as do all guys who biuld big motors. they are speced at 42 ft lbs. and they do not pull out of the aluminum cases.
if u go light on them u may experiance head leaks.


Yeah and the studs get torqued to like 20-22 ft-lbs
'78 KZ1075 LTD
stage 1 head by Larry Cavanaugh
race built crank by John Pearson
Mikuni rs34's
k410 cams
back cut tranny
8" over D&G swinger
proving once again that age and treachery is better than youth and enthusiasm

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Breaking head bolts every time 14 May 2011 15:13 #450931

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Andy9802gt, What is the cause for the discrepancy between 29, the spec, and 22, the torque on the studs? That the friction of the nut on the washer adds an additional 8 ft-lbs?
1983 KZ750 L3 with 4-1 Kerker pipe and pods
1983 KZ750 L3 parts bike

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Breaking head bolts every time 14 May 2011 17:45 #450951

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staniel wrote: Andy9802gt, What is the cause for the discrepancy between 29, the spec, and 22, the torque on the studs? That the friction of the nut on the washer adds an additional 8 ft-lbs?


u are looking at 2 dif specs. 22 was for the bolts, 29 was for the nuts.2 dif sizes
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.

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~ (k) / (z)

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Breaking head bolts every time 14 May 2011 22:27 #451030

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K, I was confused by Andy's wording. He meant the head bolts are 22 and the head nuts are 29. My understanding is that the studs are the threaded rods that come up from the crank case and the head nuts tighten onto them.
1983 KZ750 L3 with 4-1 Kerker pipe and pods
1983 KZ750 L3 parts bike

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Breaking head bolts every time 15 May 2011 16:19 #451228

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staniel wrote: K, I was confused by Andy's wording. He meant the head bolts are 22 and the head nuts are 29. My understanding is that the studs are the threaded rods that come up from the crank case and the head nuts tighten onto them.


OK U HAVE ME CONFUSED NOW. LOL
when andy was replying to my post he meant the studs which thread into the cases are only torqued to 22ft. lbs. (because they go into an alum case). and the nuts that go onto the studs get torqued to a higher #. (29lbs.) in your motor. 42ft.lbs in mine.
i think thats where were at now :)
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.

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~ (k) / (z)

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Breaking head bolts every time 15 May 2011 17:32 #451237

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That's what I meant mark
'78 KZ1075 LTD
stage 1 head by Larry Cavanaugh
race built crank by John Pearson
Mikuni rs34's
k410 cams
back cut tranny
8" over D&G swinger
proving once again that age and treachery is better than youth and enthusiasm

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Breaking head bolts every time 29 May 2011 13:10 #454174

  • staniel
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I finally got a pair of replacement head bolts. I have a spare set sitting on my desk and more on the way. I will never reuse head bolts again. These things are clearly designed to be one-use.

I used my nice torque wrench to torque them up in 15 in-lbs increments, starting at about 100. The first one made it to 240 (20 ft-lbs). The second one got up to about 200, then when I turned the wrench up, it spun farther than it had on previous torque increases, so I stopped, landing somewhere around 216.
1983 KZ750 L3 with 4-1 Kerker pipe and pods
1983 KZ750 L3 parts bike

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