Ashrita Furman has set more than 600 official Guinness records since 1979 and currently holds more than 200.
They include holding the world record for holding the most world records.
The New Yorker's latest stunt took place at the National Botanic Garden of Wales, in Llanarthne.
He beat the previous 20m (65ft) record of walking while balancing a running lawnmower on his chin, with a distance of 48.85m (160ft).
Mr Furman's other world records include:
Nearby, another world record was broken at a May Day event for the most people throwing wellington boots simultaneously.
The previous record of 431 was beaten with a total of 636.
Both attempts will be verified by Guinness World Records before they become official.
A daredevil has set a new world record in Carmarthenshire by walking almost 50m while balancing a running lawnmower on his chin.