Do you guys cut them off? Do you cut a hole in the firewall?

I am messing with a Kioritz chaninsaw engine. I put the sensor and magnent hidden behind the prop hub. I have no use for the PTO.

Cut it off.
I either use my dremel or a 4-1/2 inch angle grinder with a thin cutting disc on it.[angle grinders much faster.]
I hold the grinder at an angle and work my way all around the shaft going slow as to not heat up the shaft and cook the rear seal.
The reason to hold it at a downward angle is so after its cut off it will be below the case and wont interfear with the mountng setup.
Another thing i do is add cold water as i go around the shaft.Make 2 passes,cold water,2 passes,cold water,ect...

You need the PTO to make an inline twin engine!!! <grin>

Jack

Yup,that will be my next project after i finish my BME twin.I already have a boxer twin made from 2 Echo 14cc engines.