Hello, I have a turnigy 52cc engine with about 30 flights on it in my laser. I would start the engine with my glove on and flip it about 5 times with the choke on, it would kick, then choke off , one or two more flips and it starts.runs smooth, plenty of power.
Now when I start the engine it kicks back real bad , but after the kick back when I flip it again it starts up and runs perfect. I didn't change anything, same plug, never touched the carb settings, same timing. Same gas, same prop. Any ideas what it could be?

As the ring seats it gets a better seal that could result in getting more fuel into the engine. When the engine pops and then quits with the coke on it basically floods out. It sounds to me that the additional fuel is a contributing factor. You will want to check your timing as well as having the timing advanced past 30 degrees can also be a contributing factor. Usually 28 degrees is a good all around setting. The quick and easy things to try is first lean the low needle just a smidge. If the kick back remains then move the ignition sensor a tad counter clockwise.

Could be a low speed needle issue. Try leaning it a little. I believe these had cheap clone Walbro carbs so that could be an issue too.

Could be a failing ignition sensor causing the plug to fire too soon.

Thank you speedracer, you said if I need to move the timing , move it counter clockwise , are you looking at the motor from the front of the plane or from the tail?. I will try the low end needle first. Thank you again

As if looking at the airplane nose on.

This video will help you with the timing. Dan