what am I unintentionally doing to my lawnmower?

Factual Questions
1

Not long ago I started to notice a correlation between when I sharpened on lawnmower blade (while on the mower) and having a hard time cranking it there after. I thought it was because I turned the mower up on its side to gain access to the blades. I saw some similar hard to start behavior if I had to momentarily turn the mower on its side to remove a vine or something that wrapped around the blade.

So today, I put it up on sawhorses and crawled underneath with my dremel tool to sharpen the blades. I sat it back down, and still my normally one pull to start mower dang near gave me a stroke trying to get it to start needing 20-30 pulls, then take out the plug, a little starter fluid and another 20-30 pulls. Finally it sluggishly, reluctantly, wheezily started running.

So apparently the problematic thing is something I do while sharpening the blade. I usually spin the blade around 180 degrees to sharpen the other side of the blade. Am I messing something up by spinning the blade around?

2

if you turn the mower on its side - you may be causing oil to bypass the cylandar/valves - the proper way to turn a mower up to access the bottom is with the sparkplug always facing ‘up’.

On turning the blade - first thought is that you may be allowing just enough gas into the chamber (by activating the intake valve) that it is essentially flooding it.

3

+1
Try doing it without turning the blade, or if you need to to access both of them, pull the spark plug and if there’s a strong smell of petrol, she’s flooded, and the starting fluid probably ain’t helping much.
If it is flooded, try turning off the fuel tap and pull it over 4-5 times, or until it tries to fire, should help empty the cylinder for another try.