X-carve 500mm pulley

I bought only the core and rail kit thinking i have the equivalent of everything else.I saw on the assembly tutorial i need a pulley GT2 with 18 teeth but i have a pulley GT2 with 20 teeth.
Do i have to mod the grbl firmware for the one with the 200 teeth?
Thank you.

Yes, $100, $101, $102.

thank you for information

The standard Xcarve pulley is a 20 tooth pulley I think…


Yep. If you look at the instructions for the Xcarve 1.0, it lists “Aluminum GT2 Pulley 20T 1/4in” as its pulleys for the steppers.