90% of plug fouling is caused by a too rich a fuel mixture.
Check the float level and make sure that the needle and seat is clean and cutting off the fuel supply.
The idle must too be adjusted correctly.
Set float level, make sure that all jets are clean and fuel flows freely from the float bowl drain when the screw is cracked open.
Start with air screw 1.5 turns out.
Set idle screw so that it has some sort of idle. With TORS it is the big screw under seat on top of unit. With no TORS is is the brass screw midway down carb body.
Warm up motor and then set idle screw for a faster idle, 2000rpm+
Adjust air screw either way to get the fastest idle.
Adjust air screw a little at a time leaving 10 secs or until the motor responds.
Re adjust idle screw for desired idle .