Has anyone experience this. Since I have rebuilt my engine I've had this problem it happens about 90 percent of the time when trying to start the engine. I don't have problems starting.....actually starts like in it normally should. Initially, I checked the timing...I purposely moved the dist. one tooth back and the engine ran pretty bad. The same thing happened when the moving it the other direction. I think it has a vaccum leak somewhere or a hose in the wrong place but can not figure out which one. The vaccum advance has been replaced as well. Any ideas?