then only thing that happens if you mess it up is it bends a pushrod. that's cheap to get replaced so not really a big deal to be honest. heck my mower engine bent a pushrod before adjusting the valves was even necessary. it was at like 299hrs and the manual says adjust them at 300hrs. you can't really mess up if you do it right. use the right feeler guage and use the above method. works every time.