Different piston types?

[2 strokes 4 life]

On this parts display there are different pistons for the same bike. My guess is that the A size is STD size and all the sizes going down are slightly bigger requiring a borring and plating. My question, am i right with my therory and if so which one is stock and wich one is 1st and 2nd size over?
http://www.gofasters.com/index.php?...77_539&zenid=02f9b72868c1882a710fd819d55672d0

Thanks for any help.

 

[Cruiser]

The a, b, c, etc is very slightly bigger,, and does not require boring/plating. These are to keep the tight clearances as the cylinder wears.. I think they were like,,, .0005" difference?

 

[SpeedyManiac]

They change by 0.02mm I believe. Most bikes come fitted with an 'A' piston when new (check the cylinder - it's stamped on it) and then when you rebuild it down the road you'll change to the larger pistons.

 

[2 strokes 4 life]

So i will not have to re-bore? Just mabe a replate if bad enough? If so thats realy cool. Thanks.