YZ250K Piston differences

[Boyracer]

So I got this K and bought a barrel off ebay and a piston from the US, just wondering why some 250 pistons have cut outs and some dont, it looks like J to T are the same pistons?
Thanks for any help.

[PeterC]

I suggest a search of the Wiseco pistons. Often later pistons, forged have weight reducing citouts around the wrist pin area, probably to reduce weight and make the exoansion rate uniform. It may be some are cast and some forged

[skypig]

The cutouts on the intake side of the skirt are for port timing aren’t they?
The YZ80D had an extra one above the two on the C model.

The RZ500 has different cutouts on the front pistons compared to the rear. It’s a bizarre engine with different induction F and R (case v piston port)

[2T]

Apologies for butting in with an off-topic comment.

Re: RZ500 induction.

I owned an RZ500 in the late 80's and the front cylinders always ran slightly differently from the rear, evidenced by different spark plug conditions. I always thought it was because of the different shaped expansion chambers from front to rear, making the carbies harder to tune equally. I had no idea of the other configuration differences.

Again, sorry to butt in... carry on!