what to do about intake head threads?

[moboman2003]

Hi everyone. I'm working on my 600's head right now and one of the
problems is that all the threads on the top are shot. For the two
above the exhaust I put in a couple of helicoils that are m6-1.5.
For the two next to the intake this is impossible. I pulled out a
spare junk head to test and as I tapped the new threads in for the
helicoil the wall of the intake cracked.
So I was wondering, what have you done to to replace the threads in
the head? It seems the threads around the intake are shot on all my heads.
here are a couple of pictures.
http://i6.photobucket.com/albums/y229/m ... ge0074.jpg
The one I drilled then tapped.
http://i6.photobucket.com/albums/y229/m ... ge0075.jpg
The couple of ideas I had were maybe to add just a little bit of meat
with the welder, or to use smaller bolts and smaller helicoils. Your
thoughts?
Thanks for the help,
David

[zayjspeed]

Hi
There is a repair that Kawasaki came up with in the 70's I think
called "Time-Sert" It is now in the "K&L Supply" they are way beyond
what you are doing. Yes the "H coil" will brake stuff and strip more.
Refer to page 106 of the "K&L" book 2007
:::::::::::::::::::::Zay