It`s possible I did not explain the situation well.

The engine runs great with the balance tube installed. And has for many years and hours. Smooth at all RPM`s.

When I connect the Carbmate it floods and runs really rough. In fact it won`t even keep running.

I wouldn`t think the carbs would be that far out of sync when it has been running so smoothly all along.

You may be right, though! I will start from scratch with a manual sync and adjust it from there.

Thanks for the suggestion.

Cheers
Don