The 18-year Surban lived up to expectations especially after the top bet Eusebio Quiñones decided not to join the pre-SEA Games due to fever days before the staging of the event.
Surban was deadly yesterday and he dedicated his performance to his wife, who is expected to deliver their first baby next month.
He easily negotiated the 6-lap race course at 6.3 kilometers per lap in 2 hours, 7 minutes and 13.73 seconds.
The victory, on the other hand, came out sweeter as he was able to extract revenge to Thailand's Tawatchai Masae, who placed better than him in the last Asian Mountainbike Championships in Bali, Indonesia.
Masae clocked 2:11.06.65.
Fellow RP team member March McQuinn Aleanar also surprise the field to win the bronze in 2:15.10.50.
Singapore's Tan Hong Chun and Samuel Yang ended fourth and fifth respectively while RP bet Jojo Cortes was sixth.
Singapore rider Junaidi Bin Hashim stopped after the second lap and former Thailand track champion Thanawat Somana quit during the penultimate lap.
In the distaff side, veteran Marites Bitbit went way ahead of her opponents but crashed in the middle of the third of the four-lap race.
Bitbit looked so tensed and too wary of Thailand's Jirapon Jantharat that instead of concentrating on the route, she was seen looking behind several times that caused her the trouble. She did not finish.
Jantharat won the gold in 1:41.26.63 while Nitzel Montebon, the other RP female rider, who was way behind Bitbit, finished with a silver in 2:01.29.32. NATIONAL OPEN
Just like in the downhill event last Saturday, the experts class of the cross-country competition saw former RP mainstay Hilario Ladra dominating the field over former RP pool member, Evic Largo as Earl Vince Cadampog secured the third spot.
In the women's action, Jasmin Lasota's comeback was good enough after winning the title over another returning female rider, Grace Bascon as Salvie Lou Makiling went away with the third place honors.
Joseph Diez, on the other hand, crossed the finish line ahead of a strong field under the senior class including RP downhillers Michael Borja and Joey Barba who ended third and fourth placers, respectively.
In the junior side, Julius Diez outsmarted Earl Planta.
The other division saw Noel Famor coming out the fastest in the veterans class (30-34 years olds), Roland Pasaol in the 35-29 bracket and Jemuel Moreno winning the beginner's class.