Bolt that holds on jug has broken!

Jewell

Sponsoring Member
Oct 23, 2000
118
0
My 97 Kx 125 has seen better days. One of the bolts that holds on the jug has broken off down inside the case. I'm sending my whole engine to Mr. Gorr this winter and was wondering if this is something he can take care of when he does the case split. Has this happened to anyone else? I haven't tried an easy-out on it but I think it might work. Any suggestions.

By the way I'm back!:p
 

MikeT

~SPONSOR~
Jan 17, 2001
4,112
11
Ask Eric, but how about anti-seize. Would that work?
 

smb_racing

Master of None
LIFETIME SPONSOR
Jul 31, 2000
2,085
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hey jewell good to see ya back buddy, eric can remove the broken part and put in a new stud when he does the other engine work, just make sure you tell him to do so. It's not a very complex process really, you could probably fix it yourself with a left handed drill or an ez out.
 

Coach in ND

Member
Mar 19, 2001
212
0
I had this happen on my '98 KX 125. Both cylinder mounting studs on the front of the cylinder let go about half way through a moto.

I used an E-Z out to remove them. Came out real easy.

Anybody have any idea why this happens??? I was told it was cause I over torqued them but I have only heard of it happening on KX's!!

Coach
 

smooth sail

Member
Dec 10, 2001
42
0
I'm really interested on this thread. I have owned a 97 KX-125, a 2000 KX-250 and my boy has an 01 KX-125. I have never had a cylinder stud failure. However, when I recently disassembled the cylinder/head for a trip to Eric's shop on my boys 01, when I removed the power valve linkage cover, I was shocked, and amazed to find no nut on the stud at all. It was not floating around in the cover either, which leads me to believe that it was never present from the original assembly in Japan. The cylinder was being retained by 3 nuts! This bike has always run well, and was not babied, except for break-in.There was no evidence of blow-by, or leakage at the base either. I checked the parts list, and it indicates a nut should be there (I thought so too, but needed to confirm it), so when it goes back together, it will have one on it. Could these studs be breaking from frame flex torquing the head/cylinder at the headstays?
Smooth
 

jmics19067

LIFETIME SPONSOR
Jan 22, 2002
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I personally dont belive that overtorquing the bolt will break the stud. When I did that mistake I pulled the stud out of the case. The steel stud being stronger than the threads in the aluminum case.
 

whyzee

Never enough time !
LIFETIME SPONSOR
Dec 24, 2001
2,282
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personally dont belive that overtorquing the bolt will break the stud. When I did that mistake I pulled the stud out of the case. The steel stud being stronger than the threads in the aluminum case.
Are you really a mechanic? No, really? FYI it’s spelled “fleet”

The reason this happens is aluminum oxidation from the case and rust from the stud create pressure on the stud, and heat is going to weaken the stud, pressure as you remove a heat stressed nut, it snaps. Penetrating oils are our friends.

I had trouble with a dowel pin, drove me crazy. Time and patience.
 

jmics19067

LIFETIME SPONSOR
Jan 22, 2002
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Are you really a mechanic? No, really? FYI it’s spelled “fleet”


sorry I am not as perfect as you. I am talking about mistakes I have made Thought I learned something from it and wishing someone doesnt have to make the same mistake I did.


The reason this happens is aluminum oxidation from the case and rust from the stud create pressure on the stud, and heat is going to weaken the stud,


So you are saying the stud failed because it outlived its useful life in its environment . Or are you saying that proper precautions wasn't taken to prevent dissimilar metal corrosion?So it wasn't from tightening the bolt too much? Which was the issue I was addressing
 

whyzee

Never enough time !
LIFETIME SPONSOR
Dec 24, 2001
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Sorry if I came across the wrong way. I’m not claiming to be anything close to perfect, what is up with that? A mechanic would know what heat stress on a stud that has been subjected to dirt-penetration, oxidation and rust will do. Heck, all it takes is a spec of dust to lodge a bolt with a close tolerance.

I have heard of bolt and stud fractures in both installation and extraction so it is an over torque problem. You can over stress the stud on removal, THAT is over stress as well, if it breaks.

Lastly, bolts, studs, nuts, and other fasteners have a period of useful life. If the conditions are severe, then their length of service is greatly reduced. I can’t imagine applying so much torque to a stud that you would rip out the threads unless the thing was cross-threaded and had weakened the case threads
 

jmics19067

LIFETIME SPONSOR
Jan 22, 2002
2,097
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Yes I am mechanic. Yes I do make mistakes. Yes I will admit them when I believe I am wrong and someone shows me what is right. I didnt think that the opening statement of yours was very friendly.

When I am on the computer I am usually having a beer or two . I guess I took offense and tried to play captain budwieser with his beer muscles . I Am Truly Sorry.Anyway as a mechanic the main purpose of my job is to figure out what is wrong and then fix it. Not nessecarily<God I know I spelled that one wrong >
to try and figure out why it went wrong. In other words I need to crankout the wok and not think about it.

And I do know from plenty experiance that when I grab a couple of NEW nuts and bolts and the impact gun . Then proceed to have a brain fart on occasion and crank them too tight . I strip the threads off the bolt usually more so than the nut but I end up stripping something out. The only time I have broken new bolts while tightening is because something isn't lned up right . Either way you may laugh and snort at some of my work practices

If the original question of this thread<forum thread that is> is why it snapped while installing I would say that the stud had a crack in it. in which he could of looked at the broken edge of the stud and seen if there was an indication of rust that went deeper then the thread depth. If the problem was on disassambly I would say that either the threads of the nut rusted onto the stud or that the last time it was assembled the threads galled up from lack of lubrication and welded themslves together.
The dissimilar metal corrosion and the galvanic erosion because of it< I believe would be the actual terms ,but i have been wrong before and as long as I draw breath I will be wrong again> could very well pose a problem in corroding the stud away and weakening it.

I must admit that I believe I was wrong it saying it was broken because the nut was tighten to much causing the failure. I was under the impression of just the act of tightening the nut past the strength of the stud. Thinking about it more and more, I tend to beleive that the nut was tighten a little too much at last installation. I believe that with the expansion differences between aluminum and steel when hot <aluminum expanding more than the steel> put a greater stress on the bolt than it can handle from it being to close to begin with. That with corrosion weakening the stud and locking the threads together it is no wonder it failed.
If all I say comes out to be true then I would say use antisieze.a flat washer and Nylock type locknut, and a torque wrench when assembling. When disassembling look for pits in the stud from rust and or stretchmarks and cracks from the aluminum expanding from heat also from constantly trying to stretch the bolt longer each time you tighten it.That should be more than enough overkill to keep it from snapping again.
 
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