I bought a "parts saw" on eBay, from a pretty clever seller, who alleged that since he wasn't mechanically inclined, and couldn't get the saw started, he thought he'd sell it "for parts or repair." Said, it "had compression" on hand cranking, and it was a Makita DCS-6800 -- the pictures were dark and small, and at the angle they were taken from, it was difficult to draw any conclusions on the condition ... of the saw. But I apparently didn't care. To make a long story short, I jumped on it, figuring that I could probably tweak it nice, and maybe have me a new toy. A week later, the saw arrived.
Boy, this seller, an eBay hooker named "Tim," or "Elliot" or something, from a place called Lakewood, must have seen me coming. This was a parts saw alright ... as in, some very ingenious eBay-hooker took the scrap parts from several saws, and made himself up a parts saw special. (The only other option is that this one saw suffered an amount of abuse which goes beyond the record books.)
As an indication of the abuse the saw has had, the shoulders on the bar nuts are almost completely rounded, and the threading in the crankcase wall for the chain catcher bolt has been completely stripped. One of the two long muffler screws was an original torx, the other was a hex head substitute. The muffler side screw was just missing. Remove the flywheel cover (secured by 2 original torx screws, and 2 hex head substitutes), and the flywheel has a broken fin. Pull the engine off the frame, and the handle bar is bent (but usable) and one of the two front anti-vib lugs is sheared straight thru. The clutch shoes are polished 360°, and the brake band is worn down to paper thin (and its edges razor! sharp). Not even a bubble of oil rises from the oil pump from hand cranking. The rails on both sides of the 18" Makita bar (a GB pro-top) are T'd out, scalloped, and heat burned. And, the saw "has compression," just like the hooker said ... but ahhah!, only in the lower end! D#%! The cylinder has no compression whatsoever! There is no way that saw was ever used as a saw with that little compression. In fact, it takes more effort to pull the piston back down out of the cylinder than it takes to push it up into the cylinder! The piston is so badly scored, and the rings so lock-frozen-burned-in-embedded into the ring grooves at the exhaust port (plus 20° on either side), that there is no resistance on the upstroke and no compression at the top. Zilch.
Hmm, composite "parts saw"-? Hmmm, it needs new flywheel ($100), new piston and clyinder ($170), new clutch, chain brake, anti-vib connector, maybe new oil pump. Not to mention, the "few markings" which the seller alluded to (which I figured were maybe dings and scratches) turn out to be 1" by 4" "ownership gouges" in the rear handle footrest, and again in the metal clutch cover (having different numbers also). So the saw ain't clean, like the darkened pictures suggested. D#%! I must have been real horny or something for a 6800. Looks like I got my first burn on eBay, so it may as well have been a good one. ... So, what to do?
I think the scoring of the piston was caused when "the owner" stuck a screwdriver or chisel or something into the exhaust port, after he snapped a fin on the flywheel, maybe to to pull the clutch. The top of the piston has a 1/16" deep gouge at the lip, and there is a snag in the top opening of the exhaust port in the cylinder wall, at exactly at same place. So, some kind of hard sharp object was jammed into the exhaust port, and then the crank was leaned on. I'm guessing that the last time the was started, the flame front "got around" to the side of the piston at that ding, where it quickly cooked the side of the piston at the exhaust port ... the side wall heat then accelerated into local seizure and buildup of more heat and carbon grunge, which further ground up the piston walls, and heat-compacted the metal-carbon grunge into the ring grooves, seizing the rings and killing compression (in the cylinder that is-- lol).
My first goal is to just get the thing started if I can ... so I rekkon I need me some compression. I tried straight 2-cycle oil. Hopeless! The gouges in the piston are too deep! Air just blows right by them. Amazingly, the cylinder walls are scratched up, as in not perfect, but they are not nearly as bad -- being of a *much harder material than the piston. So, I took some emery cloth to "polish" (LOL) the grunge and stuff off the cylinder walls just above the exhaust port. I also "smoothed" down the nick in the top lip of the exhaust port opening. (How much damage can I do to a cylinder that is probably going to be chucked anyway.) To free up the piston rings ... I tried heat (to no avail) and "circumferential pushing" where I inserted a solid copper spacer into each ring gap and then tried to mechanically squeeze the excess circumference around the piston to the seized up area, so as to push the ring out of the groove (also, to no avail). Those rings are heat seized into their grooves or something.
Anybody have any ideas on how I might free up the seized rings, so I can maybe get this thing started ... or, should I just ... heave it and call it a lesson learned? (Or, anybody have a used but serviceable type 'A1' piston for a 6800? Just about anything will do.) What should I do next? (I don't think I'm going to hassle with trying to "get justice" on eBay ... I'd rather get the saw running if I can.)
Boy, this seller, an eBay hooker named "Tim," or "Elliot" or something, from a place called Lakewood, must have seen me coming. This was a parts saw alright ... as in, some very ingenious eBay-hooker took the scrap parts from several saws, and made himself up a parts saw special. (The only other option is that this one saw suffered an amount of abuse which goes beyond the record books.)
As an indication of the abuse the saw has had, the shoulders on the bar nuts are almost completely rounded, and the threading in the crankcase wall for the chain catcher bolt has been completely stripped. One of the two long muffler screws was an original torx, the other was a hex head substitute. The muffler side screw was just missing. Remove the flywheel cover (secured by 2 original torx screws, and 2 hex head substitutes), and the flywheel has a broken fin. Pull the engine off the frame, and the handle bar is bent (but usable) and one of the two front anti-vib lugs is sheared straight thru. The clutch shoes are polished 360°, and the brake band is worn down to paper thin (and its edges razor! sharp). Not even a bubble of oil rises from the oil pump from hand cranking. The rails on both sides of the 18" Makita bar (a GB pro-top) are T'd out, scalloped, and heat burned. And, the saw "has compression," just like the hooker said ... but ahhah!, only in the lower end! D#%! The cylinder has no compression whatsoever! There is no way that saw was ever used as a saw with that little compression. In fact, it takes more effort to pull the piston back down out of the cylinder than it takes to push it up into the cylinder! The piston is so badly scored, and the rings so lock-frozen-burned-in-embedded into the ring grooves at the exhaust port (plus 20° on either side), that there is no resistance on the upstroke and no compression at the top. Zilch.
Hmm, composite "parts saw"-? Hmmm, it needs new flywheel ($100), new piston and clyinder ($170), new clutch, chain brake, anti-vib connector, maybe new oil pump. Not to mention, the "few markings" which the seller alluded to (which I figured were maybe dings and scratches) turn out to be 1" by 4" "ownership gouges" in the rear handle footrest, and again in the metal clutch cover (having different numbers also). So the saw ain't clean, like the darkened pictures suggested. D#%! I must have been real horny or something for a 6800. Looks like I got my first burn on eBay, so it may as well have been a good one. ... So, what to do?
I think the scoring of the piston was caused when "the owner" stuck a screwdriver or chisel or something into the exhaust port, after he snapped a fin on the flywheel, maybe to to pull the clutch. The top of the piston has a 1/16" deep gouge at the lip, and there is a snag in the top opening of the exhaust port in the cylinder wall, at exactly at same place. So, some kind of hard sharp object was jammed into the exhaust port, and then the crank was leaned on. I'm guessing that the last time the was started, the flame front "got around" to the side of the piston at that ding, where it quickly cooked the side of the piston at the exhaust port ... the side wall heat then accelerated into local seizure and buildup of more heat and carbon grunge, which further ground up the piston walls, and heat-compacted the metal-carbon grunge into the ring grooves, seizing the rings and killing compression (in the cylinder that is-- lol).
My first goal is to just get the thing started if I can ... so I rekkon I need me some compression. I tried straight 2-cycle oil. Hopeless! The gouges in the piston are too deep! Air just blows right by them. Amazingly, the cylinder walls are scratched up, as in not perfect, but they are not nearly as bad -- being of a *much harder material than the piston. So, I took some emery cloth to "polish" (LOL) the grunge and stuff off the cylinder walls just above the exhaust port. I also "smoothed" down the nick in the top lip of the exhaust port opening. (How much damage can I do to a cylinder that is probably going to be chucked anyway.) To free up the piston rings ... I tried heat (to no avail) and "circumferential pushing" where I inserted a solid copper spacer into each ring gap and then tried to mechanically squeeze the excess circumference around the piston to the seized up area, so as to push the ring out of the groove (also, to no avail). Those rings are heat seized into their grooves or something.
Anybody have any ideas on how I might free up the seized rings, so I can maybe get this thing started ... or, should I just ... heave it and call it a lesson learned? (Or, anybody have a used but serviceable type 'A1' piston for a 6800? Just about anything will do.) What should I do next? (I don't think I'm going to hassle with trying to "get justice" on eBay ... I'd rather get the saw running if I can.)
And that's what buying saws on Ebay, on the chance of a quick fix, is. On the up side, you already got an offer for $50 for some parts, and you could probably part out the rest, to ease a little pain. Before you put any $$ into it, I'd have the bottom end checked out. You could also shelve it and wait for another one to come up in running but smashed condition and then combine the two. 
