I've never bought parts using any VIN number or motor ID number. Year, make, and model are all that should be needed. I just looked up a piston for a kd80. From 1980 to 1985 is the same part number.
As far as being on the fence with the site, well, that's understandable. It's a quirky place with a core group of oddballs. One either feels comfortable here, or they leave.
And that is why we are still here (maybe in and out) after all these years.
I'm on the fence about you, too. Not alot about this shows you have mechanical knowledge.
Engine numbers are irrelevant, nobody is asking you for engine numbers.
In the real world
You measure a removed piston and cylinder to see what size they currently have installed.
Then you see if there is a reason to bore, hone, or replate.
If so, you purchase the appropriately sized piston based on the measurements taken, or OEM and send off for a re-plate/bore job. you only need a year make and model.
once all the new components are there, you measure them again and see that the clearances are correct per the manual.
So tell me again.
How was the 1985 piston "wrong?"
Were you even going to consider the wrist pin bearing?
-BIG DAN
Mechanics 101, Did lovesick change his name and reappear?
OP only wanted to know the year of his bike from the vin!
But starts off with an engine number.
I just want to see pics of this fabulous time machine.
And I just want to see Nurse Lisa again.
So, OP got his answer, and is gone like a fart in the wind.