last winter i made 1 engine out of 3 11 hp briggs and come up with enough parts to have 1 complete.it runs rough for a while and always throws the keeper on the intake valve.could this be a clerance problem or some other problem causing this.the parts engines were all identical i honed the cilinder and installed new rings also did the valves.i dont know what the valve clerance should be and how to go about corecting it.any info on this project greatly apreciated as to why it would throw the keeper