The gasket between the carb and block is different, and the pulse channel in some of the blocks doesn't go far enough and is too close to the hole for the carb, so if the gasket is missing or not exactly in place the pulse will leak...Horizon needs to look closer at the blocks they supply t
They have the right idea, the execution leaves something to be desired..
The carb would fill with fuel when choked if there were no pulse channel at all, and sometimes will barely run with the pulse channel completely closed...did it yesterday, forgot to put the pulse channel in a carb block I made for a conversion...