1990 kx125 with 91 piston?

[kdxohio]

I just bought 2 1990 125 rolling chassis' with one motor and yes they are for sure 90s. I pulled the numbers on the piston that came with the motor today and its a wiseco for a 1991 engine...Is there a way I can tell what year this engine is for sure because the 90 and 91 seem to have different pistons from what I've found. I haven't found any serial number on the engine but anyone can throw a 91 piston in a 90 motor so I just want to make sure I put the correct one in.

[sandblaster]

Without a engine ID number it will be hard.
88-90 kx125 used KX125FE00xxxx
91 used KX125HE00XXXX
If you don't have the number, look at the cylinder.
A 90 cylinder will have 1602 embossed on the cylinder behind the left exhaust valve cover.
A 91 cylinder will have 1645 embossed on the cylinder behind the left exhaust valve cover.
A 90 will use a KEIHIN PWK V56 carburetor.
A 91 will use a KEIHIN PWK V675 carburetor.
A 90 head should have 1316 embossed on it.
A 91 head should have 1344 embossed on it.
More info here:
http://www.oem-cycle.com/KX125KAWASAKIBIKEID.shtml

[kdxohio]

Awesome thanks for the response man Ill check that out tonight when I get home I need to make my formal introduction to the site still too. I may have overlooked the number on the cases but I'm pretty sure its not there.

[kdxohio]

Well Ive got the 1645 on the cylinder and v675 on the carb that along with the 91 piston safe to assume its a 91 motor

[sandblaster]

Yep