That ring looks suspiciously dirty, carbonized. Very possible "some event" convinced dad something was going bad, he parked the bike and decades later junior finished the job.
Bent valves are often very subtle don't see the bend till it's removed and spun.
The debris from what ever destroyed the piston could bend a valve also. The minimal damage from such a big event is almost odd. Results of a sticking valve event in a "it just stopped running" bike I bought.
In any case might be a lesson here about how quickly to go back to WFO operation in a recently out of the barn bike?
I'm big on internal lubing and several hundred times spinning over the motor by foot or starter before firing it up.
You'll have check the bores then see what piston might be the best fit, desired compression for your use. Hint there are still big bore kits to be found at a reasonable price https://yamahaxs650.com/product/447-big-bore-kit-80mm-750cc/
Bent valves are often very subtle don't see the bend till it's removed and spun.
The debris from what ever destroyed the piston could bend a valve also. The minimal damage from such a big event is almost odd. Results of a sticking valve event in a "it just stopped running" bike I bought.
In any case might be a lesson here about how quickly to go back to WFO operation in a recently out of the barn bike?
I'm big on internal lubing and several hundred times spinning over the motor by foot or starter before firing it up.
You'll have check the bores then see what piston might be the best fit, desired compression for your use. Hint there are still big bore kits to be found at a reasonable price https://yamahaxs650.com/product/447-big-bore-kit-80mm-750cc/
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