There is a youtube video of someone doing it to a honda hr215 like you have. I am not sure if you have the origional hr215 or the hr215k1 mower as the valve clearance MAY be different but I cannot remember. If you look at your model # and Serial #, robert@honda here on the forum could probably get you some written instructions on how to do it to spec. Make sure you use good quality feeler gauges when you do it. Good Luck:thumbsup: Look at youtube and type Lawn mower repair valve adjustment. video is by IFIXIT4U but I would rather see you get all the info from robert@honda here on the forum as he IS the honda man!
