unpaid vehicle

good eve attorney, just wanted to ask i sold a motorcycle to a friend back in 2009 we had a notarized letter stating he will pay the full amount of 10,000. after ondoy the paper was lost and he kept on making excuses that since he was also flooded he cannot pay us for the mean time.he still owes us 5000 pesos it came to a point were in he was using abusive language stating that we do not understand his situation which is absurd since we were also flood victims. we never saw him or heard of him again until yesterday we saw him using the motorcycle, it has been registered to lto already. do i have legal right to sue him since i have witnesses of the said agreement? what would be the steps that i can do to force him to pay.

send a demand letter by registered mail. if you live in the same city, file a case at his bgy first then a small claims case. rules on sc.judiciary.gov.ph