Motorcycle Questions? Ask a Mechanic.
a 100 psi reading is pretty low so that certainly won't help
have you tried adding a little engine oil to each cylinder and repeating the measurement?
as if the compression pressure leaps up then you know its an issue with the bore and piston rings
if it stays low with oil then you know its the valves not sealing
so if thats what you get its worth pulling the cylinder head off and replacing the valves and lapping them in to repair any damage to the valve seats