For moto travel to Mexico, bring both the passport and the passport card.
Use one or the other for the TVIP/tourist card, keep the other hidden on the bike as your "get out of jail free" token should you lose the primary.
Once you get to the Guatemala border, they'll want to see your passport book with an exit stamp from Mexico. You can ice your passport card once you get here, it's of no use Guatemala on down.
No stamp, no entry into Guatemala.