The visitors looked to be cruising after building a 17-0 lead, but a brave home fight back saw Ynysybwl cut the deficit to seven points coming into a nervous final few minutes. RGC1404 had the last word with a penalty and now sit proudly on top of the table ahead of their first home game of the season this weekend against Tredegar.
Tredegar, meanwhile, remain stuck at the other end of the table after suffering a crushing 32-7 home defeat against Mountain Ash, who rounded off their first win of the campaign with a try bonus point.
Rhydyfelin lost ground on the leaders as they were overpowered 31-18 at home by Penallta, while there were wins on the road for Ystrad Rhondda, 16-12, and Rumney, 17-9, at Treorchy.
In Division 2 East, Nelson hit Fleur de Lys for six as they secured the full five points in a 39-17 away win. That victory moved them past Pill Harriers to the top of the table. Following their narrow 20-14 defeat at Bedlinog, the Harriers now lie in third place behind the unbeaten Senghenydd, who were the bye team this weekend.
Caerphilly moved to the top of Division 3 East thanks to a hard fought 14-8 home victory over Abercarn, while Gwernyfed just edged it over Croesyceilliog to win 30-28. Their try bonus allowed them to move away from the bottom.
In Division 5 East, Nantyglo cruised past Usk 60-17 to remain at the top and are now the only unbeaten team in the division. Elsewhere, there was late drama at Llanhilleth as three tries were scored in the last five minutes to give the home side a 19-14 triumph over Brynithel.
Pontyclun were comfortable winners in Division 3 South East as they scored eight tries in a 55-0 home romp against Porth. Tonyrefail picked up their first points of the campaign courtesy of a 21-21 draw at home to Fairwater.