DT125R '89 Engine Number

Hi guys,

Anyone out there with an 89 DT125R which they know still has the original block in it. I've just checked mine and it has 3MB00 on it. I cant find anything on tinterwebz that says this is right (in fact things that say its wrong).

I need to do the top end and know that the piston sizes differ 88-89 (56.40mm) and 90 onwards (56.00mm).

Then i guess then ive gotta see if its already been bored total PITA getting a 2nd hand bike, i wanna know everything

Thanks in advance guys

$t0F