Re: Is this SLOW? Video....
Re: Is this SLOW? Video....
Again, it looks to me like your running at about 1800 rpm under light load, when you load the motor or accelerate, it's either leaning out or dropping a coil or plug. Both can be affected by load and RPM, I've had many engines run fine at idle or low rpm, yet break up and shudder when under load or accelerated.
You need to determine whether it's fuel or spark that's causing it to drop a cylinder, a timing light is a good suggestion to check for spark. If you don't see the spark drop out on one of the coils, try as suggested above and spray some fuel mix into each carb to see if that smooths out the engine. It's not a rev limiter issue, you have a problem and it will takes some hands on diagnosis to find it.