Sawdustmaker
Addicted to ArboristSite
This is a Pro Mac 850 that a freind of mine bought new in '77. It has alot of sentimental value to him. but it locked up on him. so now i have to find a pm850 p/c for it. but what caused this?
Is this a ring snag, or what?
- Thread starter Sawdustmaker
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Nope. Ring snag will usually break the ring and tear up the ring grooves with it. That looks like lack of lube or a lean seizure.
Or is that a huge groove in the piston deeper than the ring groove? Still doesn't look like ring snag to me. May have something to do with all the carbon too. Reguardless, I don't think that cylinder will live to run another day anyway.
ericjeeper
Addicted to ArboristSite
Looks like if he cared about it.. He should have mixed some oil in his gasoline.
gink595
Addicted to ArboristSite
Eric, you're so PC and gentle with your opinions. Kind of reminds me of my myself sometimes
Sawdustmaker
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He loaned it out, And it came back like this. any tips on unlocking it to get the jug off?
ericjeeper
Addicted to ArboristSite
If you love something never loan it out..especially anything two stroked.
as for getting it to release the jug? Might take an old sparkplug and knock the porcelain out and weld in a grease zerk. and pump it full . Note the will only move it to below the highest port.
as for getting it to release the jug? Might take an old sparkplug and knock the porcelain out and weld in a grease zerk. and pump it full . Note the will only move it to below the highest port.
It ran with straight gas. I'm sorry it happened, but do not loan out saws.
7oaks
DRUGSTORE LOGGER
Tzed250
Addicted to ArboristSite
McCullochs of that vintage are unit construction, or "clamshell" designs. No separate cylinder. 850 crankcases go for high dollar.
I would say you have a pretty slim chance of getting it apart.After saying that,here is what I might try.Carefully use acid in the cylinder to try and weaken or break some of the adhesion points.If this is a clamshell design,as was suggested,drop the pan and see if there is enough clearance to twist the piston in the bore.You might have to pull the bearings to gain enough clearance to turn the crank side to side and get the piston moving in the bore.All in all,a lot of trouble and potentially dangerous, but I know you are familiar with using the acid and will work out a safe plan.Once you get it (the piston) moving a bit,even just side to side,you have a chance of getting it out.Good luck and be safe,take it slow if you try this.
stinkbait
Addicted to ArboristSite
I would tell your friend that he needs to find a parts saw with a good engine. If it's worth a lot to him, that would be an easy fix.
I think I recall reading about somebody's father in law toasting the saw anyway. "Seein as how you was loanin me your saw and all, I couldn't see using up your gas too, so I bought my own and straight gassed your saw for ya."
Getting it apart is no problem. Take the saw all the way down and pull the crank. You will be left with the top half of the cylinder/crankcase. Cut the top off the cylinder of and drive the piston and rod assembly out. Most likely the cylinder is gone so I would not worry about hurting it. The saw could have had a cracked intake boot and caused the lean run.
Biker Dude
Addicted to ArboristSite
Good luck finding a P&C for an 850! The last parts saw that came up on feebay went for $255. I've been looking for one for a few months now without any luck. Bob in NY might have a P&C for $200 or so.
Yet another example of the violation of Rule #1. Never loan your saws. :chainsawguy:
