There has been some discussion in the club about primers lately and I would like to share a few facts for those interested.
As you may or may not know, the primer pumps fuel directly into the manifold upstream of the intake valve and does not go through the carburetor. If you leave the primer unlocked, fuel can get sucked through the primer in addition to the fuel going through the carburetor. That creates an extremely rich mixture. To the point where the engine may run rough or in extreme cases, not at all. Bottom line is that with an unlocked primer, you will run extremely rich to the point of running very rough.
Hope this clarifies the questions people have been asking.