Can I Notarize A Letter About Someone Wanting To Take Over Payments On A Vehicle?

It's up to you, but it is still "not" going to release the owner of the motorcycle from the responsibility of the original loan. It would be better for the guy to have the bike refinanced into his name. The finance company is not going to honor that notarized paper if the payments are not made. They will come after the original owner for payment and his credit will be ruined if he does not pay. Also there is the matter of license tag and insurance. If the original owner has the bike financed then his name is on the title until the loan is paid off. What if the new owner wrecks the motorcycle? It would be better if they go to the company where the motorcycle is financed through.

Yes. Notarizing something is just stating that you have looked at the persons I.D. And the signature on the letter/document is theirs. Have both parties involved sign the letter of intent.

You would have to take it to a notary public... I would call your local courthouse