i have a briggs 19.5 twin and have rebuilt the motor due to someone running it with a broken oil slinger, once i had it all back together i can turn it by hand but once i put plugs in the starter will not spin it. i change batteries, changed the starter and still the same. i had looked in the book to see what it said about timing but only shows to line up the marks which i have done twice, i can get it to turn some but it will not fire and turns like it is out of time. is there anything special about setting the timing on these engines? is there a compression release in this engine?