I too have a 3W which sometimes kicks back, and does it hard. Mine is a 75i, with about 5 hours running, and has done it since new. I have run it with a friend's (new) ignition unit, with the same result. The ignition units are not getting hot. The static ignition timing is set at a few degrees after TDC. After a number of painful experiences I finally came to my senses and started to use a chicken stick rather than a glove. I have sent the engine back to 3W but they returned it with no fault found. It is still kicking back and I have just broken a second prop on the stick during a kickback. It is getting expensive! With the carb set to the factory settings it does not kick back, but the main needle is way too rich. With the needle set 5/8 of a turn out rather than one, the engine runs well but kicks.

Can anyone help please?