Yz450f 2015 intermittent issue heureuse needed

[nicky-san]

Here are the symptoms

motor shuts-off ramdomly on Landings then reignites 

motor weak on bottom end but normal at peak

motor sound like muffler packing is burnt at bottom, ok on top

i cleaned the pickup coil to spark plug electrical connections and changes the plug for good measure 

It worked ok in the beginning but at 35 min it start to get worst until it shuts of on Landings and then  re-ignites

other symptoms re-appeared 

needless to say i am scared of running it again until i Know what it is

can someone Help me with diagnostic?

I ordered a new set of wires to the pickup coil since the connection is not tigth

 

Tks in advance