Allen head bolts

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Kevlarr

Kevlarr

New Member
Jul 22, 2009
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Just wondering if this has happened to anyone else.
Last year I switched out my front studs to allen head bolts since a lot of people here had suggested it, I went a step further and added collars between the motor and the front strap so there wouldn't be any side pressure from tightening the the bolts. Well a week after I put them in the head on one of the allen bolts pops off as I was doing my pre-flight torquing routine so I switched back to a spare stud I had laying around plus I added a sheet metal screw through the strap into the frame for insurance.

Well my insurance payed off last night in the middle of a ride. I was cruising along when I heard a little "pop", there didn't seem to be anything wrong as far as how the bike ran or felt so I chalked it up as maybe hitting a stone and it popped out from the side of the tire. It was after dark when I got home so I just parked the bike in the garage. This morning I noticed that the surviving allen head bolt was missing the head and the only thing that kept me from being stranded about 10 miles from home was my little sheet metal screw "insurance".

I'm beginning to think that the allen head bolts are too brittle to use for motor mounts.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
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Littleton, Colorado
Kev,
Any fastener can be over stressed with resulting failure. I do not subscribe to the idea of tightening fasteners. You can visually inspect the critical ones looking for open lock washers or any signs that they are loose but the mistake that I see so many people make is to try to get a turn, even a slight amout of turn on fasteners after they have been tightened correctly initially. There is a big difference between checking a fastener and tightening one. Constant retightening is an invitation for failure. That being said you should also check the quality of the fasteners you're using. All too often the big box stores and even some hardware stores sell poor quality items. I don't want to mention any country of origin but most of those bad bolts come from the same place your engine did. :)
Tom
 
bairdco

bairdco

a guy who makes cool bikes
Aug 18, 2009
6,537
264
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living the dream in southern california
only allen bolt i broke was when my chain came off and whipped into my motor mount, breaking both of them. i use them on all my builds and never had any other problem with them.

if it wasn't for that motor mount in the way, the chain probably would broke my ankle, or my a$$.

i agree with Tom, if any of my bolts look loose, i put a wrench on them and see if they'll turn. if they don't, i don't force them. i think i've only tightened a motor mount bolt once, and it was maybe 1/8th of a turn.

i also seem to do my pre-ride checks when i'm 30 miles from home, while stopping to stretch and have a smoke. luckily, my chains only seem to break within 4 blocks of my house.
 
GoFastBicycles

GoFastBicycles

New Member
Jul 29, 2008
557
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West Point PA.
I was thinking to myself today that I must be lucky with all my builds(13). I have had no issues with loose nuts. I think some are over thinking on this,which leeds to paranoia,which leeds to over tight fasteners. I do check before all rides to be safe.

Adam
 
Maxvision

Maxvision

New Member
Jun 13, 2009
551
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San Diego, CA
I don't know who's luckier. My bike started running weird one day. Right when it started running weird I saw this brown thing fly off the bike. I turned around and picked it up to see what it was. It was dog poop that flew off my wheel...ewww...stink finger all the way home!
 
M

meowy84

Member
Jul 18, 2009
239
0
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Canada
2door said:
I don't want to mention any country of origin but most of those bad bolts come from the same place your engine did. :)
Tom
Click to expand...
You're a sneaky one trying to get that one past our sharp intellects :) LOL

In the words of a great President:
"There's an old saying in Tennessee — I know it's in Texas, probably in Tennessee — that says, fool me once, shame on — shame on you. Fool me — you can't get fooled again."
 
Last edited:
charles.paskell

charles.paskell

New Member
Feb 25, 2010
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NC
Maxvision said:
I don't know who's luckier. My bike started running weird one day. Right when it started running weird I saw this brown thing fly off the bike. I turned around and picked it up to see what it was. It was dog poop that flew off my wheel...ewww...stink finger all the way home!
Click to expand...
Sorry man I had to say that was funny
 
mapbike

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Kevlarr said:
Just wondering if this has happened to anyone else.
Last year I switched out my front studs to allen head bolts since a lot of people here had suggested it, I went a step further and added collars between the motor and the front strap so there wouldn't be any side pressure from tightening the the bolts. Well a week after I put them in the head on one of the allen bolts pops off as I was doing my pre-flight torquing routine so I switched back to a spare stud I had laying around plus I added a sheet metal screw through the strap into the frame for insurance.

Well my insurance payed off last night in the middle of a ride. I was cruising along when I heard a little "pop", there didn't seem to be anything wrong as far as how the bike ran or felt so I chalked it up as maybe hitting a stone and it popped out from the side of the tire. It was after dark when I got home so I just parked the bike in the garage. This morning I noticed that the surviving allen head bolt was missing the head and the only thing that kept me from being stranded about 10 miles from home was my little sheet metal screw "insurance".

I'm beginning to think that the allen head bolts are too brittle to use for motor mounts.
Click to expand...
I use grade 5 allen head bolts on every area I can get them for on my motors and have not had any issues with them, only problems I have ever had was trying to use the original studs that that were so soft they would strip out or break from vibration, My Allen Bolts are holding up well on my bike with 653miles on it and not even a hick-up with the bolts. I just put some Loc-tite (blue) on mine snug them up good and then give them a slight tweak and they stay put, I dont even use loc-tite on the side cover bolts and they have never came out or got loose.
hope you get it all worked out.
Shan
 
B

Buzzard

Member
Jul 9, 2008
264
5
18
Lincoln, NE
All American made bolts have an SAE standard torque value in relevance to hardness. Always use a torque wrench for the fastener being used and you know it will be set right. If you have ever worked on carbon fiber bikes you won't touch them with a 10ft pole without a torque wrench. Either in inch pounds or foot pounds
 
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