Black spark plug!?

[Deleted]

I have a 72cc kit, original air filter but open no restriction.
My scooter run #1, top speed 47 mph!
Today i check the spark plug and it was black, the motor was turn idle around 3 minutes

Pilot jet # 35
Main jet # 88
Needle jet clip : middle

The mixture screw is adjust only at ½ turn (open) if i give more the idle is rough or the motor die. But at ½ turn, when the motor is hot no problem with the idle or acceleration. When the motor is cold the idle is up and down until the motor is hot, after that it's #1!

Did something can i do to have a better adjustement ?

Thank's

[90GTVert]

It's possible that it's a little rich somewhere, but if it's doing that speed and you have no complaints riding I'd be tempted to leave it alone. It's pretty normal for engines to run rich at idle anyway. I think all GY6 50s do that stupid cold idle. My old one seemed to do that no matter what I tried and I had a lot of setups on it. It might have stopped with the 150 carb, but I'm not sure on that, it's been a while. Not worth swapping carbs anyway, I got worse gas mileage and worse throttle response. I'd rather have a rough cold idle.