Yesterday i decided to change the oil myself since i had the free time. My last oil changed was done at the local yamaha-kawi dealer that i purchased my bike from.

Upon removing the oil filter i noticed that there was no washer between the spring and the oil filter. Should i be worried about this? I have a lot of miles under my belt without that washer and i wonder if it cause any sort of negative wear. Unfortunately, since i had to have the bike back up and running by days end to go somewhere i reinstalled the filter and continued without the washer.

I even managed to strip the main oil filter bolt (it was a long/bad day) trying to untighten it. (I used 17mm but didn't remove fairing). Everything is back on and there are no leaks as of yet. I was just curious if i should be worried and just reorder the bolt and the washer and just change the oil again?

......I was just curious if i should be worried and just reorder the bolt and the washer and just change the oil again?

The washer protects the bottom of the filter from the direct contact of the spring, but most filters are strong enough at that point and suffer no damage.

You could file the head down to 16 mm, but only if you did not use a six-point socket for loosen the bolt as you should.