dont think we ever concluded whether or not Swiss Intervalves from Motobins were a good upgrade.
What appealed to me I think was that they were not 2 part
I had a valve break on an old ex plod 80 rt. completely knackered the head, piston and barrel. soon fixed though. I would never take the chance again. My current RT has done 55000 so I have done the valves and guides.
It is actually the wear in the guides that causes the problem, not the valve.
the wear in the guide allows the stem to move side to side which puts a strain on the head of the valve. Exhaust valves seen to suffer more than the inlet valve.