Trailing 27-15 at the interval against last season's impressive Division 3 East champions, Abercynon had to work flat out to bridge the gap and avoid a second successive defeat at the start of the season.
Former Youth team lock Sean Brown had a debut to remember as he scored the first of his the visitors' tries, but ended the game in hospital after fracturing his collar bone. Other tries came from Gavin Hole and Garreg Legge to complete the fightback.
The only consolation for the home side, for who Chris Sulway scored two tries, were two losing bonus points as they outscored their visitors by five tries to four.
There were also nine tries in Llantrisant's 33-26 home win over Treorchy, who also picked up two losing bonus points, while Ynysybwl stayed on top of the table thanks to their 23-22 victory at Rhydyfelin.
The visitors had scrum half Nathan Ellis to thank for victory at the death as he kept his cool to land a last play penalty to win the game. The home side outscored their visitors by four tries to three and looked set to take maximum points, but in the end had to settle for a mere two losing bonus points.
Mountain Ash bagged four tries in their 22-0 home win over Penallta, while Llantwit Fardre were 25-15 victors on the road at Brynmawr. Tries from Dan Fox and David Davies earned Newport Saracens a 15-6 home triumph over Gilfach Goch.
Abergavenny ran in six tries in their 45-28 victory at Pill Harriers to ensure maximum points from their opening two games in Division 3 East, while Croesyceiliog were the only other side in the division to earn at attacking bonus point with their four tires in a 35-12 home win over Tredegar Ironsides.
There were eight tries for New Tredegar in their 46-5 home win over Nantyglo in Division 4 East, Craig Thomas getting two of them and also adding three conversions, while Abertillery BG, Abercarn and Monmouth also made it two wins out of two.
Aberbeeg and Forgeside shared eight tries in their 22-22 draw in Division 6 East, while Cefn Fforest ran in 11 in their 83-3 win at Blaina United in the same division.
In Division 6 Central, table topping Cambrian Welfare ran in seven tries in their 47-3 hammering of visitors Llandrindod Wells. Julian Huntely grabbed two of them and also knocked over six conversions for a match tally of 22 points.