Sorry, but the truth is, I never got PLA to work right on a makerbot without jams.
Typically, lower is better so for sure, do not run the heated bed above 80C. PLA actually melts and stays soft at about 140C so basically, at normal 100-115C heated bed, it won't cool and just make a giant blob. Some PLA runs near ABS temps, others need much lower and I tired running at 180C. Funny part here is that heat is the enemy because it makes the PLA soft through the pinch wheels and further, on a MK6, soft in the stainless tube which then also makes jams.
Also, I would think that 1.75 is damn near impossible with PLA, especially in a MK6. It's might work in the MK7 but that fan blowing on the fins had better be hard wired to 12 volts all the time. On off fan is not going to work and you will jam.