First time joining a forum great to be here ok heres my headache I have a 8 hp tecumseh motor on a craftsman snow blower wasnt running so I did a carb rebuilt which ive done many times to simalar engines everything went well now it starts runs great for 2 minutes thrn backfires I directed my attention to the head gasket and spark plug after that I found my valves intake and exoust are out ....the exoust clearence from stem to valve lifter is .011 and intake is .012 ive done some reserch and found that the intake should be at .008 is this correct ??? If so what would be the steps for closeing that small gap!? The exoust valve could be filed down to achive the correct clearence but im some what stumped on the steps to close the gap if thrres to much ! New lifter? Valve seat re drilled pleas3 help !!!!!!!!!