KZ750 Staying on high revs.
 

Hi, guys.
I own a 1980 KZ750.
The bike ran fine when i bought it, but a couple weeks ago the carbs were leaking gas, I changed the neoprene needles and readjust the floaters and that was it, no more leaks.
Since I fixed that, while riding (no choke), the bike suddenly gets up to 3k to 4k RPM and wont go down, even in neutral shift. Also, this problem sometimes presents in the opposite way. When I stop or when I **** to neutral, the bike's RPM start decreasing until the bike turns off.

Do you know what could cause this and how to fix it?

Best regards.
Ride safe.