[Mike Taylor 3601]

When lap valve if valve is good will have ring all the way around valve, if it does valve is good,seat can be off and valve will lap in,it will contact highest spot on seat and leave ring all the way around valve.
seat should have ring all the way around seat 360*,if doesn't seat needs to be cut or ground so you have 45* all the way around, will most likely end up wide on one side narrow on other,then take 30* and 60* and narrow 45 until it is even width all the way around,probably .075-.100'' wide.
Should be able to lap valve about 30 seconds by hand and it have rings all the way around valve and seat,when correct. Can use machinist dye/layout fluid if needed to see better.

Billy,
I agree with you most of the time,but I half way disagree on this,exhaust get away with a little leak,intake not gonna get away with much of a leak,with out blowing fuel back up the runners.
Or is there more to your comment,like buddy of mine that worked on mowers,came in one day while I was putting seats in a Briggs twin,common for them to fall out,he told me electronic ignition caused that,???? he said when had points,got a set yearly,got all grass cleaned out of cooling fins,electronic doesn't get cleaned out so runs hot seats fall out,LOL
Mike Taylor 3601