Stripped head stud/engine disassembly

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LAguyyy

LAguyyy

Super Skilled Master Newb
Feb 25, 2013
37
0
0
Honolulu, hi
So my 80/66 china girl now has a stripped head stud in the lower block. This occurred by slight over torquing the steel bolt on the nice soft aluminum block. I seek help on how to efficiently repair the threads. This is the rear right stud which now spins freely. I have lost almost all compression with severe squeal coming from head cover so she is garaged. I have limited tools but love to shop for them. I heard helicoil is most effective or just drill tap to next larger sized. Is it a 6mm now and go 8mm. Any valid suggestions will help along with how to disasemble engine for the repair, I am a newbie and wish not destroy an engine with 50 miles on it that is a 40+mph engine with my arrow torquer II exhaust. :-||
 

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Wickedest1

Wickedest1

Member
Oct 31, 2012
688
7
18
41
connecticut
Exactly what you said In the first post...best 2 options...i personally have never used a helicoil...but have drilled and tapped...works very well...ditch the acorn nuts immediately...and bring the stud to the hardware store...should be able to tell you the size...
 
donphantasmo

donphantasmo

Member
Oct 3, 2010
372
11
18
Middleburg, FL
I had the same thing happen to me on a classic scooter (Vespa). I tried to find some Helicoils, but couldn't find any that were the correct size/tpi count (Teeth Per Inch). So, I decided to go a little bigger mounting bolts, and just re-tap it. I went to harbor freight, and got a great little Tap-n-dye set for $30. It payed for itself by now. Also, like Wicked said, ditch the acorns, and get some real nuts (no pun intended). And don't over torque. You're talking about cast aluminum, not very strong, so don't torque to 200 Ft/lbs.
 
LAguyyy

LAguyyy

Super Skilled Master Newb
Feb 25, 2013
37
0
0
Honolulu, hi
Picked up a huge tap and die kit at auto parts store. My head bolts are 8mm/1.25 so will see if a 10mm will fit through the head. I heard I can use a bolt threaded all down it and just destroy the mid threads if needed to torque it in. Couldn't find helicoils in Hawaii so I'll go larger and not over torque. I'm afraid of using alumni weld and heating the block to +750 degrees so I'll go old school. Got the new workbench set up about to pull engine and disassemble upper. Can't wait. If I'm wrong on this someone let me know. :-||
 
Otto

Otto

New Member
Nov 23, 2012
104
0
0
Forney, TX
LAguyyy said:
Picked up a huge tap and die kit at auto parts store. My head bolts are 8mm/1.25 so will see if a 10mm will fit through the head. I heard I can use a bolt threaded all down it and just destroy the mid threads if needed to torque it in. Couldn't find helicoils in Hawaii so I'll go larger and not over torque. I'm afraid of using alumni weld and heating the block to +750 degrees so I'll go old school. Got the new workbench set up about to pull engine and disassemble upper. Can't wait. If I'm wrong on this someone let me know. :-||
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Good luck with the larger studs. I'm guessing you might measure the 10mm nuts for clearance to the head fins as the slightly larger socket may not fit. Mine seems tight with the stock 8mm acorn socket.
 
LAguyyy

LAguyyy

Super Skilled Master Newb
Feb 25, 2013
37
0
0
Honolulu, hi
The 8mm sits loose so I might be lucky with a 10. After disassembly ill just take the head to the shop and cross my fingers. Thanks for the heads up.
 
LAguyyy

LAguyyy

Super Skilled Master Newb
Feb 25, 2013
37
0
0
Honolulu, hi
Just installed helicoil 8mm/1.25. It required no drilling and was so great I installed them on all my head bolts. The engine went back together like a champ and now I got to replace some gaskets and use seal so I'm happy. Haven't put it on the bike yet but she's a happy china girl now! Thanks for the help everyone.
 
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