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Yz250 2 stroke barrel differences

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hi All,

has anyone had much to do with barrel differences in the Yz250's? i have a 1999 2 stroke barrel in reasonable shape, but its collecting dust.

i have a spare 2007 yz250 2 stroke that im rebuilding.

 

i know the 1999 barrel will bolt straight to the 2007 case, but im wondering about porting/powervalve differences. can anyone shed any light for me?

 

1999 part number; 5CU-11311-02

2007 part number; 5UP-11311-20

 

i have access to a machine shop, so im considering boring the 1999 barrel out to 72mm and fitting a 71.96mm wiseco piston to make a yz300.

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Porting supposedly changed in '03 to the current spec. Not sure about 99-02. If you slug out the cyl you're going to need a replate, but I'm sure you know that.

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