How much metal can you remove from a piston top?

[MX?]

I need to deepen the valve cutaways in my XL piston. Assuming I work out how much meat I have in the crown of the piston is there some kind of "safe" thickness of material to leave?

[Curly3]

Ckeck the standard clearence and take as little as is needed, don't forget you'll reduce the compression.

[vmx42]

Hey MX,
A bit of a chicken and egg senario here [IMHO].

I would first measure the clearance between the valves and the piston [using putty and sliver solder]. After careful measurement if there isn't enough clearance I would measure the thickness of the piston crown.

Other more knowledgeable OzVMXers can probably tell you the minimum clearance numbers for your engine. But I think you need to know the extent of the problem first…

Good luck
VMX42

[noisy toy]

Maybe go to the wreckers and get an old piston and drill a hole in it. I have a buggered xt600 Wiseco piston if yours is Wiseco, I can drill a hole through the crown and measure if you want.