cylinder studs overtorqued into crankcase, heli-coil repair?

[Chuck78]

So Greg, maybe you could clear things up for me a little bit from your post, are you saying yes, remove the stud and drill it out for a helicoil? Or are you saying just remove the stud and use a countersink bit to remove the raised portion of aluminum?
I am thinking that all of this stud's threads in the case are compromised at this point, and I don't think the stud itself is stretched in the thread area. Three studs total, the one with the Starrett straight edge and feeler gauges is the worst.

if the studs are still available from Suzuki, I will do that. If I cannot get the stud out without hurting it, I will just disassemble another one of my spare engines and hope those cases are better. This is the only one that probably has ever been apart and had the potential to be over torqued by an amateur home mechanic. 77 - 78 GS, same as KZ, where they would leak from the front of the cam chain tunnel area on the head gasket, I assume that is why it has and Athena base gasket on it from the previous owner. They pulled the top end and put and Athena base gasket in it for some reason or another. And then neglected to do any valve adjustments, was far out of spec when my wife got it. Needed valve job.

[bwringer]

I'd get the studs out first, clean the schmoo out of the threads, and see what the threads and the studs look and feel like.

I've had good luck getting these things out with double-nutting and a little heat to soften the thread locker (although it's hard to keep much heat in the stud when it's embedded in aluminum.)

This may sound a little odd, but try several different 10X1.25 nuts from various sources and suppliers. I've found that some fit looser or tighter than others.

The shock stud nuts are deep acorns and the same thread; may be worth a try.

[Chuck78]

Thanks for the guidance, all...

FYI the bikes with smaller displacement per cylinder use M8x1.25 instead of M10. The GS750+ fours & GS400+ twins are M10, while the 550/650& & presumably the GS125, 250, & perhaps the 300(? maybe not) are M8?
Making it a lot more critical to not over-torque the stud nuts!!!!

[GregT]

Yes, pull them and inspect. If you have to, helicoil. If not, just ensure the studs are bottoming in the tapped hole.
I'd lightly countersink all the stud holes just to ensure a true surface.

When torquing the head nuts up it's imperative to lube them well. With 8mm headstuds the difference dry/lubed can be about 6 ft/lb.
Small honda fours with 6mm studs, it's even worse....