I have a 2016 Powermore (MTD) 140cc 21" push mower that I'm using to cut a 15,000 sqft lawn. I've never really bothered to mess with the spark plug on this thing. It's never fired up on the first pull, and it's been running a bit off this year with worse cold starts, occasional misfires, and feeling down on power in general. I finally decided to look at the spark plug which was a Torch brand F5RTC plug. It didn't look bad aside from having a tight gap of just .018". I replaced it with what was available at my local O'Reilly's which was an NGK BPR5EIX-11 iridium plug with a .043" gap. The first pull after replacing that plug, it fired right up, and has fired up on the first pull ever since. No more misfires and it seems to have some pep back to it as it holds rpm better in thicker grass.
To see if the gap was the issue, not the plug, I opened the gap on the Torch plug to .035" and put it back in. The hard starts and misfires came back so it was definitely the plug, not the gap.
To see if the gap was the issue, not the plug, I opened the gap on the Torch plug to .035" and put it back in. The hard starts and misfires came back so it was definitely the plug, not the gap.