In the off chance there is anyone interested in the continuing progress of clearing the dead Oak threatening my utility lines, I offer this update:
Yesterday after a refresher vacation at the beach I awoke to temps in the 50's and decided to saw up the tops and haul them to a more convenient place to split and stack them.
I had used my Dolmar ps 421 on the Maple limb that fell on our Church building last week and knew it had half a tank of mix and I believed the 16" bar would be sufficient for most of this cutting. I filled the bar oil and fuel in the garage (clue 1). And Scout and I strolled down the drive to the farthest tree. I sawed that tree top up handily and began sawing next farthest tree top. Eventually my chain jumped the bar. I shut down the saw and noticed (clue 2) the bar oil cap was missing:
Hmmm, don't think that ever happened to me before, and can't imagine the combination of forces required to unscrew and then pull the cap and tether out of the tank.
Next I pulled the sprocket cover to reset the chain. That's when I noticed the chain was bone dry (clue 3) as a result of running dry. When I removed the chain it was so dry and stiff there were links that wouldn't straighten out (clue 4):
Not good, I couldn't get it to track straight in the bar groove. My usual response to this kind of puzzle: lunch break. After lunch Scout and I went back to scene of the jumped chain in search of the cap. I'll include two pics from that tree as (clue 5 & 6) in case one of you have better eyes and spot it laying there among the saw dust, rounds, and poison ivy:
I couldn't find it, but guessed the saw probably ran for a while before it got so dry it spit the chain. I move back in reverse order of sawing sites till I found these rounds with significant oil spill ( clue 7):
I thought I finally was in the right area and searched thoroughly but found nothing.
Then Scout reminded me that these oiled rounds are certainly where the cap loosened, but the cap probably stayed tethered for some time before popping out and dropping.
Smart dog, we searched for a while, but soon decided it was futile.
So, back to the house and Google where I found part number 181 114 202, list price $5.62 plus about twice that much shipping.
Fortunately, my local dealer had a cap which though Dolmar (Now Makita) have different part numbers, we quickly determined the cap for a PS 5105 was the same functional part. This dealer declared the chain "end of useful life" so I replaced it, he also was concerned the oil pump was probably destroyed by running dry for any length of time. We filled it with mix and bar oil and quickly verified the pump was working fine.
Back out this morning fully expecting to find the cap now that I have replaced it. No problem, I'll have a spare.
My much smarter dog has watched me sweat, slip, slide, and grunt a bunch of these rounds up the steep incline to my ATV and cart. He'll just stay up there and observe.
Thanks for all comments, related or not. And thanks for checking out my long posts with probably too many pictures.