Paramotor engine out. Any ideas???

symptoms:
flew for around 35mins when the the engine just shuddered or felt like it stalled whilst at around 3/4 power. It then felt like it lost power in an intermittent bogging way.
I cruised it for another 30mins or so before it did it all again but bogged all the down to the engine conking out and I couldn't restart it.
On the ground the plug looked perfect. the HT cap had a small split in it and the carb looked clean however it was the original carb kit on a 129hr engine. primer bulb and hoses all new..
suggestions:
clunk
breather cap
HT cap
CDi unit
kill switch
air bubbles in fuel line
reed valve