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Author Topic: Hayabusa head stud problem  (Read 105 times)

Offline firemanjim

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Hayabusa head stud problem
« on: February 12, 2018, 10:18:07 PM »
I have been building a mild motor for my street bike with accumulated parts over time. Put in APE head studs--- cannot remember if the first set was brand new or not now, but torquing the head to the recommended per APE tech spec page of 65 lbs I snapped a dang stud. Broke part way down the top threaded area. Pulled the head and replaced it, only to break a second at about 60 lbs. Again, off with the head replaced it again, and-- you guessed it-- a third let go. Gave up and called APE as I was looking at their site and the catalog section calls for 60 lbs but the tech and spec section says 65. Pat was surprised to hear of the breakage and suggested maybe my torque wrench was off. I got a second wrench and torqued a wheel nut to compare and they are even. So-- WTF :?
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Offline Stainless1

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Re: Hayabusa head stud problem
« Reply #1 on: February 12, 2018, 10:39:59 PM »
Jim,  were you dry or lubed and were the threads lubed or the threads, nut and washer?  I don't remember what is called out on those, but if the lube is just threads and you lube nut to washer as well it is easy to over torque. 
And of course if they were previously over torqued.... all bets are off....
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Online RansomT

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Re: Hayabusa head stud problem
« Reply #2 on: February 13, 2018, 12:04:58 PM »
I've seen [reused] APE studs [10mm] break at just shy of 60lbs, like 59.  Had it happen on my "all motor bike" last year.  Don't know the history on the bolts, came with the engine I purchased.


On this winter build, I just purchased new ones, no issues.
« Last Edit: February 13, 2018, 12:10:55 PM by RansomT »
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Offline firemanjim

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Re: Hayabusa head stud problem
« Reply #3 on: February 13, 2018, 01:07:11 PM »
Looking at the APE instructions on line it does not really say oiled or dry--- and I think the first ones that broke were brand new, then a replacement from used bin broke so pretty sure from 2 separate batches?? Where did yours break?

Stainless, not headed to Aus this year-- saving for possibility of Bolivia.
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www.jtsperformance.com
Home of one of the fastest 750cc bikes in the world
239MPH faired, 209MPH naked!
Bonneville 200 Club
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Mojave Magnum 200 Club
NEDRA 100 MPH Club
Gairdner 200MPH Achiever 2013
2014 1st place Mojave Mile N/A bike
2015 top speed trophy at WOS
Colorado mile 200 MPH club
2017 DLRA 200 MPH club

Online RansomT

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Re: Hayabusa head stud problem
« Reply #4 on: February 13, 2018, 06:12:18 PM »
Broke same place.


Talk to Eric today at the shop and he confirmed that we have had several studs break over the years.  He said he usually can "feel" them give right before they break; he stops and then replaces them with new.  Happens typically on bikes that have unknown history.  60lbs is the correct torque valve for those.
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