Join Date: Nov 2009
Location: Lander, Wyoming
It kind of depends on the design of the tap. Its apparently deep enough to thread a 8 x1.25 Helicoil re-tap into, which incidentally is ever So Close to the same Diameter as a true 10 x 1.25 tap it ain't funny. If the tap has a non-essential pointy tip on it, they can be blunted/squared-off on with a grinder.
I can see about 5-6 mm of space between the frame rail & the backside of the stock captured nuts on my bike. Thats about 3-4 threads of available protrusion.
That should be enough space for most 10 x 1.25 taps to fully cut the threads.
Modify at "YOUR OWN RISK"!
Still riding my 1987 KL650-A1. 85,000+ miles & counting