u/BigChungai

Hey everyone, Im new to this sub so sorry if this post seems weird.

Im trying to help someone out with their 2004 Yamaha. star 650.
At idle and when decelerating from higher RPMs, the second cylinder constantly pops. When we tried doing a sync test on the carbs the second cylinder had almost no vacuum. Second cylinder also runs hotter (by touch) and the spark plug is slightly black like its running rich.
Verified cylinder timing and valve clearances, compression is around 150psi
I have checked all the vacuum lines, checked the carburetor diaphragms and cleaned the carbs multiple times. Im kinda running out of ideas on what could be causing this. Any help is appreciated