1992 Yamaha Pro 50 electrical problem?

[gbftats7]

I have a 1992 yamaha pro 50 with TDR reeds, and a shaved head. Motor was just rebuilt and im having what seems to be an electrical issue.

When the motor is running there is a spark arcing off of the butterfly valve inside the carburetor. It happens randomly between all 3 carbs and it kills the cylinder when it happens. But it only happens at idle. I put a volt meter against the carb and it is showing voltage when the arc happens. I have went through the entire loom and fixed any open wires, i have checked the reeds and they are all seated perfectly, I have replaced the stator and still can not find the problem.

[99yam40]

could this be static electricity jumping to the engine caused by carbs not being grounded to the block?

air flow past the throttle plates builds up static electricity.
the gaskets and thread sealant on bolts keeping metal to metal contact?

where/what are your meter leads hooked to ?
and what is the voltage reading?