353 e-tech

Can anyone tell me the purpose of the circled part in the attached picture? Nothing was attached to it when dissembled and can't find anything in manuals so far. Also, any opinions of the 44.3mm vs 45mm top ends? This saw will be mostly used for cutting eastern white pine regen and invasive...

Hi all. I have a 353 e-tech, stock. I've had it a couple years now, no problems until today. I was using it the other day cutting some railroad ties (just a couple cuts), no problem, until the very end of the last cut, when I let off the throttle it just died. I didn't think much of it but did...